From Carnegie Mellon University: “Prototype Particle Detector Project Smashes Milestone”

From Carnegie Mellon University

1.31.23
Jocelyn Duffy
Mellon College of Science
jhduffy@andrew.cmu.edu
412-268-9982

Carnegie Mellon University physicists are one step closer to a major upgrade for the Large Hadron Collider’s Compact Muon Solenoid experiment.

A team based in the Department of Physics has built and tested prototypes for the High-Granularity Calorimeter (HGC), an upgrade to the current Compact Muon Solenoid detector at CERN’s Large Hadron Collider. The team includes, from left, first row: Amy Germer, a senior in physics and mathematical sciences; Valentina Dutta, an assistant professor; second row: John Alison, an assistant professor; Sindhu Murthy, a doctoral student; Manfred Paulini, a professor of physics; third row: Eric Day, a technician; Jessica Parshook, an engineer on the project; Patrick Bryant, a research associate; and Andrew Roberts, a doctoral student. Credit: CMU.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map. Credit: CERN.

https://cms.cern/news/w-z-and-higgs-bosons-portals-exotic-physics

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Compact Muon Solenoid Detector.

SixTRack CERN LHC particles.

A team led by John Alison, an assistant professor in physics, and Manfred Paulini, a professor of physics and the Mellon College of Science associate dean for faculty and graduate affairs, has successfully built and tested prototypes for the High-Granularity Calorimeter (HGC), an upgrade to the current CMS detector. On the one hand, building functional prototypes is a major milestone several years in the making. On the other hand, the milestone is the first step in a manufacturing project that will take place over the next three years.

“CMS can be thought of as a large 3D camera that records the products of the proton-proton collisions provided by the LHC,” Alison said. “For example, images collected from the detector were used to discover the Higgs boson in 2012.”

Since the discovery of the Higgs boson, a major focus of the particle physics has been in studying the properties of the Higgs boson in detail and searching for new particles not predicted by the standard model of particle physics.

European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) ATLAS Higgs Event June 18, 2012.

European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)CMS Higgs Event May 27, 2012.

Comparing measurements to predictions will allow new theories to be tested but more data is needed.

The LHC has a 15-year program to increase the total number of proton collisions by a factor of 20. This program requires collecting more data faster and comes at a significant cost: increased radiation. In addition to producing new exotic states of matter — like the Higgs boson — LHC proton collisions produce large amounts of ionizing radiation. This radiation is similar to that produced by a nuclear reactor and is damaging to people and the instrumentation that makes up the detector.

Built almost 20 years ago, the current CMS detector was not designed to handle the amount of radiation damage anticipated during future LHC runs. New, upgraded detectors are needed both to improve the quality of the recorded images and cope with the more challenging radiation environment. This is where the High-Granularity Calorimeter upgrade comes in.

High-Granularity Calorimeter. Credit: CERN.

Big Data Gets Bigger

The HGC will replace current CMS detectors in regions that face the most radiation. A next-generation imaging calorimeter, the HGC will significantly increase the precision with which the LHC collisions are imaged. The number of individual measurements per picture will increase from about 20,000 in current detectors to about 6 million in the HGC. The measurements of individual particles will go from the handful of numbers that the current detector provides to a high-resolution 3D movie of how the particles interact when traversing the detector.

The HGC will be built in the next five years, and Carnegie Mellon is playing a leading role in its construction. The HGC will be composed of 30,000 20-centimeter hexagonal modules. The modules — essentially radiation tolerant digital cameras — will be tiled to form wheels several meters in diameter. The wheels will then be stacked to form the full 3D detector. In total, the HGC will require 600 square meters of active silicon sensors.

Alison, Paulini and Valentina Dutta, a new assistant professor in physics, will build and test 5,000 of these modules in Wean Hall laboratory with the help of engineers, technicians and students. The remaining modules will be produced by CMS collaborators at The University of California-Santa Barbara and Texas Tech University in the U.S., and by groups in China, India and Taiwan. Each module consists of a silicon sensor attached to a printed circuit board housing readout electronics and to a base plate, which provides overall stability.

Module construction will be performed with a series of automated robots that use pattern-recognition algorithms for assembly and then the required approximately 500 electrical connections per module are established. After a series of testing at CMU the modules are tiled onto wheels at Fermilab — a particle physics lab outside of Chicago — and then sent to CERN in Switzerland for installation in the CMS detector.

The production of the first working modules this fall was part of a qualifying exercise in which the various assembly centers demonstrated that they are ready and able to build the high-quality modules needed by HGC.

The CMU group established a class 1,000 clean room on the eighth floor of Wean Hall, expanding an existing space used by the medium-energy physics group. They have installed and commissioned an 8,000-pound gantry robot to attach the different module layers and an automated wire bonder to make the electrical connections within the modules. The prototype modules allowed the group to test its automated assembly procedures and exercise the full production chain.

“It is great to see our group achieving this qualification milestone,” Paulini said. “I had been working diligently for some years to bring this project to CMU since it also offers opportunities for graduate and especially undergraduate students to obtain hands-on instrumentation experience working in our lab during the semester or for summer research.”

Producing a handful of modules to specification is just the beginning. During full-scale module production — starting in 2024 — CMU will produce 12 modules per day until early 2026. A major challenge in ramping throughput will be recruiting and onboarding local talent.

“To meet production needs we have to grow the group with hiring four more full-time technicians and engineers who will work on the daily production line,” said Jessica Parshook, the lead engineer for Carnegie Mellon’s project team.

Developing and implementing reliable test procedures for quality control is another major challenge going forward. The production pipeline requires several days to build each module. Catching and fixing any flaws in production quickly will be critical. Postdoctoral fellows and graduate students will create most of the assembly and quality control procedures that will provide opportunities for a significant number of CMU undergraduates to get hands-on experience testing modern particle physics detectors.

“Our efforts here could lead to the next big discovery in physics and that excites me,” said Sindhu Murthy, a doctoral student in physics. “In these early stages of setting up production, I get to see the different aspects of an engineering project of this scale. It’s a great experience and a privilege to contribute to this upgrade. I’m always thinking about how we can optimize module assembly so that everything goes as planned.”

Alison, Dutta and Paulini said that recent advances in image processing from machine learning will be crucial in assuring quality control during production.

“This work, a mix of computer science, machine learning and robotics, is a perfect fit for CMU and we plan to tap into resources throughout the university,” Alison said.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Carnegie Mellon University is a global research university with more than 12,000 students, 95,000 alumni, and 5,000 faculty and staff.

Carnegie Mellon University has been a birthplace of innovation since its founding in 1900.

Today, we are a global leader bringing groundbreaking ideas to market and creating successful startup businesses.

Our award-winning faculty members are renowned for working closely with students to solve major scientific, technological and societal challenges. We put a strong emphasis on creating things—from art to robots. Our students are recruited by some of the world’s most innovative companies.

We have campuses in Pittsburgh, Qatar and Silicon Valley, and degree-granting programs around the world, including Africa, Asia, Australia, Europe and Latin America.

The Carnegie Mellon University was established by Andrew Carnegie as the Carnegie Technical Schools, the university became the Carnegie Institute of Technology in 1912 and began granting four-year degrees. In 1967, the Carnegie Institute of Technology merged with the Mellon Institute of Industrial Research, formerly a part of the The University of Pittsburgh. Since then, the university has operated as a single institution.

The Carnegie Mellon University has seven colleges and independent schools, including the College of Engineering, College of Fine Arts, Dietrich College of Humanities and Social Sciences, Mellon College of Science, Tepper School of Business, Heinz College of Information Systems and Public Policy, and the School of Computer Science. The Carnegie Mellon University has its main campus located 3 miles (5 km) from Downtown Pittsburgh, and the university also has over a dozen degree-granting locations in six continents, including degree-granting campuses in Qatar and Silicon Valley.

Past and present faculty and alumni include 20 Nobel Prize laureates, 13 Turing Award winners, 23 Members of the American Academy of Arts and Sciences, 22 Fellows of the American Association for the Advancement of Science , 79 Members of the National Academies, 124 Emmy Award winners, 47 Tony Award laureates, and 10 Academy Award winners. Carnegie Mellon enrolls 14,799 students from 117 countries and employs 1,400 faculty members.

Research

Carnegie Mellon University is classified among “R1: Doctoral Universities – Very High Research Activity”. For the 2006 fiscal year, the Carnegie Mellon University spent $315 million on research. The primary recipients of this funding were the School of Computer Science ($100.3 million), the Software Engineering Institute ($71.7 million), the College of Engineering ($48.5 million), and the Mellon College of Science ($47.7 million). The research money comes largely from federal sources, with a federal investment of $277.6 million. The federal agencies that invest the most money are the National Science Foundation and the Department of Defense, which contribute 26% and 23.4% of the total Carnegie Mellon University research budget respectively.

The recognition of Carnegie Mellon University as one of the best research facilities in the nation has a long history—as early as the 1987 Federal budget Carnegie Mellon University was ranked as third in the amount of research dollars with $41.5 million, with only Massachusetts Institute of Technology and Johns Hopkins University receiving more research funds from the Department of Defense.

The Pittsburgh Supercomputing Center is a joint effort between Carnegie Mellon University, University of Pittsburgh, and Westinghouse Electric Company. Pittsburgh Supercomputing Center was founded in 1986 by its two scientific directors, Dr. Ralph Roskies of the University of Pittsburgh and Dr. Michael Levine of Carnegie Mellon. Pittsburgh Supercomputing Center is a leading partner in the TeraGrid, The National Science Foundation’s cyberinfrastructure program.

Scarab lunar rover is being developed by the RI.

The Robotics Institute (RI) is a division of the School of Computer Science and considered to be one of the leading centers of robotics research in the world. The Field Robotics Center (FRC) has developed a number of significant robots, including Sandstorm and H1ghlander, which finished second and third in the DARPA Grand Challenge, and Boss, which won the DARPA Urban Challenge. The Robotics Institute has partnered with a spinoff company, Astrobotic Technology Inc., to land a CMU robot on the moon by 2016 in pursuit of the Google Lunar XPrize. The robot, known as Andy, is designed to explore lunar pits, which might include entrances to caves. The RI is primarily sited at Carnegie Mellon University ‘s main campus in Newell-Simon hall.

The Software Engineering Institute (SEI) is a federally funded research and development center sponsored by the U.S. Department of Defense and operated by Carnegie Mellon University, with offices in Pittsburgh, Pennsylvania, USA; Arlington, Virginia, and Frankfurt, Germany. The SEI publishes books on software engineering for industry, government and military applications and practices. The organization is known for its Capability Maturity Model (CMM) and Capability Maturity Model Integration (CMMI), which identify essential elements of effective system and software engineering processes and can be used to rate the level of an organization’s capability for producing quality systems. The SEI is also the home of CERT/CC, the federally funded computer security organization. The CERT Program’s primary goals are to ensure that appropriate technology and systems management practices are used to resist attacks on networked systems and to limit damage and ensure continuity of critical services subsequent to attacks, accidents, or failures.

The Human–Computer Interaction Institute (HCII) is a division of the School of Computer Science and is considered one of the leading centers of human–computer interaction research, integrating computer science, design, social science, and learning science. Such interdisciplinary collaboration is the hallmark of research done throughout the university.

The Language Technologies Institute (LTI) is another unit of the School of Computer Science and is famous for being one of the leading research centers in the area of language technologies. The primary research focus of the institute is on machine translation, speech recognition, speech synthesis, information retrieval, parsing and information extraction. Until 1996, the institute existed as the Center for Machine Translation that was established in 1986. From 1996 onwards, it started awarding graduate degrees and the name was changed to Language Technologies Institute.

Carnegie Mellon is also home to the Carnegie School of management and economics. This intellectual school grew out of the Tepper School of Business in the 1950s and 1960s and focused on the intersection of behavioralism and management. Several management theories, most notably bounded rationality and the behavioral theory of the firm, were established by Carnegie School management scientists and economists.

Carnegie Mellon also develops cross-disciplinary and university-wide institutes and initiatives to take advantage of strengths in various colleges and departments and develop solutions in critical social and technical problems. To date, these have included the Cylab Security and Privacy Institute, the Wilton E. Scott Institute for Energy Innovation, the Neuroscience Institute (formerly known as BrainHub), the Simon Initiative, and the Disruptive Healthcare Technology Institute.

Carnegie Mellon has made a concerted effort to attract corporate research labs, offices, and partnerships to the Pittsburgh campus. Apple Inc., Intel, Google, Microsoft, Disney, Facebook, IBM, General Motors, Bombardier Inc., Yahoo!, Uber, Tata Consultancy Services, Ansys, Boeing, Robert Bosch GmbH, and the Rand Corporation have established a presence on or near campus. In collaboration with Intel, Carnegie Mellon has pioneered research into claytronics.

From CERN [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH): “7.2-m-long niobium–tin quadrupole magnet manufactured at CERN reaches nominal current for the first time”

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

From CERN [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)

1.25.23

The 7.2-metre-long version of this vital HL-LHC component reached nominal current plus an operational margin corresponding to a coil peak field of 11.5 T at 1.9 K during a test in SM18.

The MQXFBP3 magnet after the test, during assembly with the nested dipole orbit corrector. (Image: CERN)

Another success for the HL-LHC magnet programme: after the successful endurance test of a 4.2-metre-long niobium–tin quadrupole magnet in the United States in spring 2022, the HL-LHC quadrupole’s longer version proved its worth later in the year.

The MQXFA05 magnet enters the vertical cryostat at the Brookhaven National Laboratory for its endurance test (Image: BNL)

“MQXFBP3”, the third full-length quadrupole prototype to be tested at SM18, reached nominal current plus an operational margin in September–October 2022, confirming the success of the niobium–tin technology for superconducting magnets.

MQXFBP3 is the third in the series of HL-LHC triplet quadrupoles that have been produced and tested at CERN in recent years. These 7.2-metre-long superconducting magnets, along with their shorter counterparts currently being produced in the United States, will focus proton beams more tightly around the ATLAS and CMS collision points to allow the tenfold increase in integrated luminosity (the number of collisions) targeted by the HL-LHC.

The first two magnets tested at CERN fell short of reaching nominal current, which prompted the Accelerator Technology department’s magnet group to improve the design and the assembly processes of its prototypes as part of the so-called “three-leg strategy”. The magnet cold mass was reworked to reduce the coupling between the welded outer stainless-steel shell and the aluminium structure of the magnet.

The MQXFBP3 magnet on its way to reaching nominal current in SM18. (Image: CERN)

This updated version – the third prototype – was able to reach nominal current (corresponding to 7 TeV in operation) plus 300 A of operational margin with only one training quench at 1.9 K. This is the first MQXF cold mass assembly, tested horizontally with a welded outer shell (as in the final configuration), to achieve this performance, which corresponds to a peak field in the coil of 11.5 T. The magnet has been subjected to two warm-up–cooldown cycles, showing no performance degradation. Even though the magnet satisfies the acceptance criteria for operation in HL-LHC, the magnet was limited 3% below nominal current at 4.5 K. The localisation and phenomenology of these quenches is very similar to those of the limiting quenches of the first and second MQXFB prototypes.

After the test, the magnet was removed from its stainless steel shell and is now being assembled with the nested dipole orbit corrector, which was provided by the Spanish institution CIEMAT. A new test in this configuration will be carried out in mid-2023. Should the test confirm its performance, MQXFBP3 will be the second Q2 cryomagnet to be installed in the IT (inner triplet) STRING.

The positive outcome of the recent test is cause for satisfaction and relief, especially as niobium–tin technologies, known to be more brittle than niobium–copper components, have come under particular scrutiny. Even so, engineers in the magnet group have more tricks up their sleeves to bring the performance of the 7.2-m-long MQXFB to the same levels obtained in the short models and in the 4.2-m-long magnets manufactured in the US: MQXFB02, the stage-two magnet of the three-leg strategy, will include further technical improvements in the magnet assembly to eliminate the coil overstress during keying and bladdering operations that was observed on the first three prototypes. The magnet community is eagerly awaiting the outcome of the magnet’s powering tests, which will continue throughout the first months of 2023 at SM18 – stay tuned!

High-Luminosity Third Nb3Sn quadrupole prototype timelapse insertion.

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

Meet CERN in a variety of places:

Quantum Diaries

Cern Courier

The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator. (Image: Julien Ordan/CERN).

THE FOUR MAJOR PROJECT COLLABORATIONS

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ATLAS another view Image Claudia Marcelloni ATLAS CERN.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALICE.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CMS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] LHCb.

LHC

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

CERN Large Electron Positron Collider

3D cut of the LHC dipole CERN LHC underground tunnel and tube.

The LHC magnets surround the beampipe along its 27 km circumference- Image CERN

CERN SixTrack LHC particles.

OTHER PROJECTS AT CERN

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AEGIS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALPHA Antimatter Factory.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALPHA-g Detector.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AMS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ASACUSA.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ATRAP.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Antiproton Decelerator.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AWAKE.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] BASE: Baryon Antibaryon Symmetry Experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] BASE instrument.

The European Organization for Nuclear Research [Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] [CERN] BASE: Baryon Antibaryon Symmetry Experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CAST Axion Solar Telescope.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CLOUD.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] COMPASS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CRIS experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] DIRAC.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] FASER experiment schematic.

CERN FASER is designed to study the interactions of high-energy neutrinos and search for new as-yet-undiscovered light and weakly interacting particles. Such particles are dominantly produced along the beam collision axis and may be long-lived particles, travelling hundreds of metres before decaying. The existence of such new particles is predicted by many models beyond the Standard Model that attempt to solve some of the biggest puzzles in physics, such as the nature of dark matter and the origin of neutrino masses.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] GBAR.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ISOLDE Looking down into the ISOLDE experimental hall.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] LHCf.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] The MoEDAL experiment- a new light on the high-energy frontier.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] NA62.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] NA64.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] n_TOF.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] TOTEM.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] UA9.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] The SPS’s new RF system.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Proto Dune.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] HiRadMat-High Radiation to Materials.

The SND@LHC experiment consists of an emulsion/tungsten target for neutrinos (yellow) interleaved with electronic tracking devices (grey), followed downstream by a detector (brown) to identify muons and measure the energy of the neutrinos. (Image: Antonio Crupano/SND@LHC)

From “CERN (CH) Courier” : “A NEW ATLAS FOR THE HIGH-LUMINOSITY ERA”

From “CERN (CH) Courier”

1.9.23
Stefan Guindon
Christian Ohm
Caterina Vernieri

Pixel perfection The ATLAS ITk, comprising strip (outer layers) and pixel (inner layers) detectors with more than five billion readout channels.

Pileup A simulated tt– event in a proton–proton collision at 14 TeV at the HL-LHC, including approximately 200 pileup interactions in the same bunch crossing. No fewer than 88 primary vertices (blue balls) are reconstructed along
the beam line, each producing many particles (orange tracks). In total, more than 2000 tracks are reconstructed in the proton–proton interactions.

ATLAS Phase II Schematic of the major upgrades to the ATLAS detector for the
HL-LHC era. (Credit: ATLAS)

The discovery of the Higgs boson at the LHC in 2012 changed the landscape of high-energy physics forever. After just a few short years of data-taking by the ATLAS and CMS experiments, this last piece of the Standard Model (SM) was proven to exist.

Standard Model of Particle Physics, Quantum Diaries.

Since then, the Higgs sector has been studied using a rapidly growing dataset and, so far, all measurements agree with the SM predictions within the experimental uncertainties. In parallel, a comprehensive programme of searches for beyond-SM processes has been carried out, resulting in strong constraints on new physics. A harvest of precise measurements of a large variety of processes, confronted with state-of-the-art theoretical predictions, has further supported the SM. However, the theory lacks explanations for, among others, the nature of dark matter, the cosmological baryon asymmetry and neutrino masses.

Importantly, the Higgs sector is related to “naturalness” problems that suggest the existence of new physics at the
TeV scale, which the LHC can probe (CERN Courier July/August 2022 p47).

The high-luminosity phase of the LHC (HL-LHC) will provide an order of magnitude more data starting from 2029, allowing precision tests of the properties of the Higgs boson and improved sensitivity to a wealth of new-physics scenarios.

The HL-LHC will deliver to each of the ATLAS and CMS experiments approximately 170 million Higgs bosons and 120,000 Higgs-boson pairs over a period of about 10 years. By extrapolating Run 2 results to the HL-LHC dataset, this will increase the precision of most Higgs-boson coupling measurements: 2–4% precision on the couplings to W, Z and third-generation fermions; and approximately 50% precision on the self-coupling by combining the ATLAS andCMS datasets. The larger dataset will also give improved sensitivity to rare vector-boson scattering processes that will offer further insights into the Higgs sector. These precision measurements could reveal discrepancies with the SM predictions, which in turn could inform us about the energy scale of beyond-SM physics. In addition to improving SM measurements, the upgraded detectors and rigger systems being developed and constructed for the HL-LHC era will enable direct searches to better target new physics with challenging signatures. To achieve these goals, it will be essential to achieve a detailed understanding ofthe detector performance as well as to measure the integrated luminosity of the collected dataset to 1% precision.

Rising to the challenge

To cope with the increased number of interactions when proton bunches collide at the HL-LHC , the ATLAS collaboration is working hard to upgrade its detectors withstate-of-the-art instrumentation and technologies. These new detectors will need to cope with challenging radiation levels, higher data rates and an extreme high-occupancy environment with up to 200 proton–proton interactions per bunch crossing (see “Pileup” figure). Upgrades will include changes to the trigger and data-acquisition systems, a completely new inner tracker, as well as a new silicon timing detector (see “ATLAS Phase II” figure).

ITk prototyping Loaded prototypes for (left) a pixel end-cap ring of the inner system and (right) a strip barrel stave of the ITk detector. Credit: ATLAS.

Clocking tracks An 8-inch prototype wafer of low-gain avalanche diodes for the High Granularity Timing Detector. Credit: ATLAS .

The trigger and data-acquisition system will need to cope with a readout rate of 1 MHz, which is about 10 times higher
than today. To achieve this, ATLAS will use a new architecture with a level-0 trigger (the first-level hardware trigger)
based on the calorimeter and muon systems. Building on the upgrades for Run 3, which started in July 2022, the calorimeter will include capabilities for triggering at higher pseudorapidity, up to |η| = 4. During HL-LHC running, the
global trigger system will be required to handle 50 Tb/s as input and to decide within 10μs whether each event should be recorded or discarded, allowing for more sophisticated algorithms to be run online for particle identification. All
the detectors will require substantial upgrades to handle the additional acceptance rates from the trigger. The readout electronics for the electromagnetic, forward and hadronic end-cap liquid-argon calorimeters, along with the hadronic tile calorimeter, will be replaced. The full calorimeter systems, segmented into 192,320 cells that are read out individually, will be read out for every bunch crossing at the full 40 MHz to provide full-granularity information to the trigger. This will require changes to both front-end electronics and off-detector components. The muon system will also see significant upgrades to the on-detector electronics of the resistive plate chambers (RPCs) and thin-gap chambers (TGCs) responsible
for triggering on muons, as well as the muon drift tubes (MDTs) responsible for measuring the curvature of the tracks precisely. The MDTs will also be used for the first time in the level-0 trigger decisions. These improvements will allow all data to be sent to the back-end at 40 MHz, removing the need for readout buffers on the detector itself. All hits in the detector will be used to perform trigger logic in hardware using field programmable gate-arrays. Additional improvements to increase the trigger acceptance for muons will come in the form of a new layer of RPCs to be installed in the inner barrel layer, along with new MDTs in the small sectors. The Muon New Small Wheel system was installed during Long Shutdown 2 (LS2) from 2019 to 2022 (CERN Courier November/December 2021 p27) and is located inside the end-cap toroid magnet containing both triggering and precision tracking chambers. Additional RPC upgrades were also made in the barrel leading up to Run 3, and the TGCs will be upgraded in the endcap region of the muon system during LS3.

State-of-the-art tracking

The success of the research programme at the HL-LHC will strongly rely on the tracking performance, which in
turn determines the ability to efficiently identify hadrons containing b and c quarks, in addition to tau and
other charged leptons. Reconstructing individual particles in the HL-LHC collision environment with thousands
of charged particles being produced within a region of about 10 cm will be very challenging. The entire tracking
system, presently consisting of pixel and strip detectors and the transition radiation tracker, will be replaced by
a new all-silicon pixel and strip tracker – the ITk. This will feature higher granularity, increased radiation hard-
ness and readout electronics that allow higher data rates and a longer trigger latency. The new pixel detector will
also extend the pseudorapidity coverage in the forward region from |η| < 2.5 to |η| < 4, increasing the acceptance
for important physics processes like vector-boson fusion (see “Pixel perfection” image, p22).

The ITk will comprise nine barrel layers, positioned at radii from 33 mm out to 1 m from the beam line, plus end-cap
rings. It will be much more complex with respect to the present ATLAS tracker, featuring 10 times the number of
strip channels and 60 times the number of pixel channels. The strip detectors will cover a total surface of 160 m^2
with 60 million readout channels, and the pixels an area of 13 m^2 with more than five billion readout channels. The
innermost layer will be populated with radiation-hard 3D sensors, with pixel cells of 25 × 100 μm 2 in the barrel
part and 50 × 50 μm 2 in the forward parts for improved tracking capabilities in the central and forward regions.
Prototypes of the end-cap ring for the inner system and of the strip barrel stave are at an advanced stage (see
“ITk prototyping” image). A unique feature of the trackers at the HL-LHC is that they will be operated for the first
time with a serial powering scheme, in which a chain of modules is powered by a constant current. If the modules
were to be powered in parallel, the high total current would lead to either high power losses or a large mass of cables
within the volume of the detector, which would impact the tracking performance.

Given the challenging conditions posed by the HL-LHC, ATLAS will construct a novel precision-timing silicon detector, the High-Granularity Timing Detector (HGTD), which provides a time resolution of 30 to 50 ps for charged particles. The detector will cover a pseudorapidity range of 2.4 < |η| < 4 and will comprise two double-sided silicon layers on each side of ATLAS with a total active area of 6.4 m^2 . The precise timing information will allow the collaboration to disentangle proton–proton interactions in the same bunch crossing in the time dimension, complementing the impressive spatial resolution of the ITk. Low-gain avalanche diodes (see “Clocking tracks” image) provide timing information that can be associated with tracks in the forward regions, where they are more difficult to assign to individual interactions using spatial information. With a timing resolution six times smaller than the temporal spread of the beam spot, tracks emanating from collisions occurring very close in space but well-separated in time can be distinguished. This is particularly important in the forward region, where reduced longitudinal impact-parameter resolution limits the performance.

Building upon the insertable B-layer cooling system used since the start of Run 2, and to reduce the material
budget, ATLAS will use a two-phase CO 2 cooling system for the entire silicon ITk and HGTD detectors. These will
allow the detectors to be cooled to around –35 °C during the entire lifetime of the HL-LHC. The low temperature is required to protect the silicon sensors from the expected high radiation dose received during their lifetime.

Two-phase CO 2 cooling is an environmentally friendly option compared to other suitable coolants. It provides a
high heat transfer at reasonable flow parameters, a low viscosity (thus reducing the material used in the detector
construction) and a well-suited temperature range for detector operations.

Luminous future

Precise knowledge of the luminosity is key for the ATLAS physics programme. To reach the goal of percent-level precision at the HL-LHC, ATLAS will upgrade the LUCID (Luminosity Cherenkov Integrating Detector) detector, a luminometer that is sensitive to charged particles produced at the interaction point. This is incredibly challenging given the number of interactions expected to be delivered by the machine, and the requirements on radiation hardness and long-term stability for the lifetime of the experiment. The HGTD will also provide online luminosity measurements on a bunch-by-bunch basis, and additional detector prototypes are being tested to provide the best possible precision for luminosity determination during HL-LHC running.

Luminometers in ATLAS provide luminosity monitoring to the LHC every one to two seconds, which is required for
efficient beam steering, machine optimisation and fast checking of running conditions. In the forward region, the
zero-degree calorimeter, which is particularly important for determining the centrality in heavy-ion collisions, is
also being redesigned for HL-LHC running.

The HL-LHC will deliver luminosities of up to 7.5 × 10^34 cm^–2 s^–1 , and ATLAS will record data at a rate 10 times higher than in Run 2. The ability to process and analyze these data depends heavily on R&D in software and computing, to make use of resource-efficient storage solutions and opportunities that paradigm-shifting improvements like heterogeneous computing, hardware accelerators and artificial intelligence can bring. This is needed to simulate and process the high-occupancy HL-LHC events, but also to provide a better theoretical description of the kinematics.

New era
The Phase-II upgrade projects described are only possible through collaborative efforts between universities
and laboratories across the world. The research teams are currently working intensely to finalize the designs,
establish the assembly and testing procedures, and in some cases start construction. They will all be installed and
commissioned during LS3 in time for the start of Run 4, currently planned for 2029.

The HL-LHC will provide an order of magnitude more data recorded with a dramatically improved ATLAS detector. It will usher in a new era of precision tests of the SM, and of the Higgs sector in particular, while also enhancing sensitivity to rare processes and beyond-SM signatures. The HL-LHC physics programme relies on the successful and timely completion of the ambitious detector upgrade projects, pioneering full-scale systems with state-of-the-art detector technologies. If nature is harboring physics beyond the SM at the TeV scale, then the HL-LHC will provide the chance to find it in the
coming decades.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

From CERN [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) LHCb Via “phys.org” : “CERN LHCb presents new measurements of rare decays that provide a high-precision test of lepton flavor universality”

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

LHCb

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] LHCb.

From CERN [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) LHCb

Via

“phys.org”

12.20.22

The LHCb experiment. Credit: CERN

Today the international LHCb collaboration at the Large Hadron Collider (LHC) presented new measurements of rare particle transformations, or decays, that provide one of the highest-precision tests yet of a key property of the Standard Model of particle physics, known as lepton flavor universality.

Standard Model of Particle Physics, Quantum Diaries.

Previous studies of these decays had hinted at intriguing tensions with the theoretical predictions, potentially due to the effects of new particles or forces. The results of the improved and wider-reaching analysis based on the full LHC dataset collected by the experiment during Run 1 and Run 2, which were presented at a seminar at CERN held this morning, are in line with the Standard Model expectation.

A central mystery of particle physics is why the 12 elementary quarks and leptons are arranged in pairs across three generations that are identical in all but mass, with ordinary matter comprising particles from the first, lightest generation. Lepton flavor universality states that the fundamental forces are blind to the generation to which a lepton belongs.

In recent years, however, an accumulation of results from LHCb and experiments in Japan and the U.S. have suggested that this might not be the case, generating cautious excitement among physicists that a more fundamental theory—perhaps one that sheds light on the Standard Model’s mysterious flavor structure—might reveal itself at the LHC.

Interest in the “flavor anomalies” peaked in March 2021, when LHCb presented new results comparing the rates at which certain B mesons, composite particles that contain beauty quarks, decay into muons and electrons. According to the theory, decays involving muons and electrons should occur at the same rate, once differences in the leptons’ masses are accounted for. But the LHCb results hinted that B mesons decay into muons at a lower rate than predicted, as indicated by the results’ statistical significance of 3.1 standard deviations from the Standard Model prediction.

The new LHCb analysis, which has been ongoing for the past five years, is more comprehensive. It considers two different B-meson decay modes simultaneously for the first time and provides better control of the background processes that can mimic the decays of B-mesons to electrons. In addition, the two decay modes are measured in two different mass regions, thus yielding four independent comparisons of the decays. The results, which supersede previous comparisons, are in excellent agreement with the principle of lepton flavor universality.

“Measurements of the ratios of rare B-meson decays to electrons and muons have generated much interest in recent years because they are theoretically ‘clean’ and show consistency with a pattern of anomalies seen in other flavor processes,” explains LHCb spokesperson Chris Parkes of the University of Manchester and CERN. “The results shown today are the product of a comprehensive study of the two main modes using our full data sample and applying new, more robust techniques. These results are compatible with the expectation of our theory.”

New datasets will allow LHCb—one of the four large experiments at the LHC at CERN—to investigate lepton flavor universality further, in addition to conducting a wider research program that includes studies of new hadrons, including the search for exotic tetraquarks and pentaquarks and investigation of the differences between matter and antimatter. An upgraded version of the experiment now in operation for LHC Run 3 will collect larger datasets that will allow even higher-precision tests of rare particle decays.

“Earlier LHCb indications of anomalies concerning lepton flavor universality triggered excitement,” says theoretical physicist Michelangelo Mangano of CERN.

“That such anomalies could potentially have been real shows just how much remains unknown, since theoretical interpretations exposed a myriad of unanticipated possible phenomena. The latest LHCb findings take nothing away from our mission to push the boundary of our knowledge further, and the search for anomalies, guided by experimental hints, goes on.”

Related research is available on the arXiv.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Meet CERN (CH) in a variety of places:

Quantum Diaries

Cern Courier (CH)

From CERN (CH) ATLAS: “ATLAS moves into top gear for Run 3”

European Organization for Nuclear Research [La Agencia Espacial Europea][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN]

Iconic view of the The European Southern Observatory [La Observatorio Europeo Austral][Observatoire européen austral][Europäische Südsternwarte](EU)(CL) CERN ATLAS detector

CERN ATLAS another view Image Claudia Marcelloni ATLAS CERN.

From CERN (CH) ATLAS

12.16.22

Event display of a pair of top quarks decaying, recorded in the ATLAS detector on 18 July 2022. (Image: CERN)

After over three years of upgrade and maintenance work, the Large Hadron Collider began its third period of operation (Run 3) in July 2022. Since then, the world’s most powerful particle accelerator has been colliding protons at a record-breaking energy of 13.6 TeV. The ATLAS collaboration has just released its first measurements of these record collisions, studying data collected in the first half of August 2022.

The researchers measured the rates of two well-known processes: the production of top-quark pairs and the production of a Z boson, which proceed through strong and electroweak interactions, respectively. The ratio of their cross sections is sensitive to the inner structure of the proton, and their measurement sets constraints on the relative probabilities that reactions are initiated by quarks and gluons.

These early measurements also validate the functionality of the ATLAS detector and its reconstruction software, which underwent many improvements in preparation for Run 3.

Physicists focused on Z-boson decays to electron and muon pairs, and on top-quark decays to a W boson and a jet – collimated sprays of particles – originating from a bottom quark. The W boson subsequently decays into one electron or muon and an invisible neutrino. As the analysis uses very early Run 3 data, physicists relied on preliminary calibrations of the leptons, jets and luminosity. These were derived promptly after the first data became available.

Figure 1: Ratio of production rates for the two processes (top-quark-pair production and Z production) for the first time at a centre-of-mass energy of 13.6 TeV. The band represents the measurement, while the square marker with the dotted error bar indicates the Standard Model prediction. Triangular markers with a dashed error bar represent the results of subsets of the data, shown separately for 4 runs of the LHC between 6 to 9 August, and for analyses considering just one of the two lepton flavours. (Image: ATLAS Collaboration/CERN)

ATLAS measured a top-quark pair to Z boson production ratio that is consistent with the Standard Model prediction within the current experimental uncertainty of 4.7%.

The calibration and corresponding uncertainties will be improved as more data is processed. Future updates of the calibration will allow researchers to measure the cross sections with greater precision.

To validate their results, physicists performed a series of cross-checks. These included measuring the ratio of the cross section each time the LHC was injected with a new fill of protons for a data-taking run.

More analyses using the Run 3 data will follow, exploiting the unprecedented energies and the increased LHC data set.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

CERN Courier (CH)

Quantum Diaries

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

CERN LHC underground tunnel and tube.

SixTRack CERN LHC particles

From CERN (CH) CMS: “CMS completes the release of its entire Run 1 proton-proton data”

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

From CERN (CH) CMS

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Compact Muon Solenoid Detector.

12.14.22

CMS has now released the complete set of proton-proton data taken from LHC Run 1, including the original findings used in the Higgs boson discovery.

European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)CMS Higgs Event May 27, 2012.

A collision event recorded by CMS in 2012, available in the latest release of CMS open data (Image: CERN)

The CMS experiment is one of the largest international scientific collaborations in history, with a broad programme of activities at the forefront of particle physics research. As of 5 December 2022, all of the proton-proton data collected by CMS during Run 1 of the Large Hadron Collider (LHC) is now available through the CERN Open Data Portal. This completes the process that started in 2014 with the experiment’s very first open data release in experimental particle physics.

Completing the delivery of its Run 1 data within 10 years reaffirms the CMS collaboration’s commitment to an open data policy. This policy embodies values laid down in the CERN Convention, which states that all research undertaken at the Laboratory must be open and available to everyone.

The newly released CMS data consists of 42 collision datasets, representing a total of 491 terabytes, taken in early and late 2012 towards the end of LHC Run 1. This data includes some of the original findings from CMS that were used to confirm the existence of the Higgs boson, which earned François Englert and Peter Higgs the 2013 Nobel Prize in Physics.

Included in the release are examples of code used to extract physics. This software has been successfully used to demonstrate the intricacies of experimental particle data taking in the CMS Open Data workshops held over the last three years. In addition, the CMS Open Data guide covers details of how physics objects can be accessed using this software, giving users the possibility to expand on this sample code for studies of their own interest.

Adaptable software samples are one of the most efficient ways of passing on the knowledge needed for research on the CMS data. “The software included in this release helps us preserve the huge efforts of the CMS Run 1 data analysts,” says Julie Hogan, one of the key contributors to the CMS Open Data workshops.

”The code samples are essential ingredients for any serious effort to use this data for research,” adds Edgar Carrera, the lead organiser of the latest workshops. “We therefore do our best to allow users of the data to follow the original CMS procedures as closely as possible.”

The preparations for the next CMS data releases are under way. The collaboration looks forward to providing additional heavy-ion open data from Run 1 and to proceeding with further Run-2 releases.

CMS Open Data workshop 2022!

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

Meet CERN (CH) in a variety of places:

Quantum Diaries

Cern Courier (CH)

From The DOE’s Brookhaven National Laboratory: “Comparison Suggests Particles of Light May Create Fluid Flow and Data-Theory”

From The DOE’s Brookhaven National Laboratory

12.13.22

Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Brookhaven Lab theorist Bjoern Schenke’s hydrodynamic calculations match up with data from collisions of photons with atomic nuclei at the Large Hadron Collider’s ATLAS detector, suggesting those collisions create a fluid of “strongly interacting” particles.

Studying “Little Bangs”: exotic collisions probe the size of quark-gluon plasma. https://atlas.cern/updates/briefing/studying-little-bangs

CERN LHC ATLAS schematic. https://www.bnl.gov/atlas/

A new computational analysis by theorists at the U.S. Department of Energy’s Brookhaven National Laboratory and Wayne State University supports the idea that photons (a.k.a. particles of light) colliding with heavy ions can create a fluid of “strongly interacting” particles. In a paper just published in Physical Review Letters [below], they show that calculations describing such a system match up with data collected by the ATLAS detector [below] at Europe’s Large Hadron Collider (LHC) [below].

As the paper explains, the calculations are based on the hydrodynamic particle flow seen in head-on collisions of various types of ions at both the LHC and the Relativistic Heavy Ion Collider (RHIC) [below], a DOE Office of Science user facility for nuclear physics research at Brookhaven Lab.

BNL RHIC. https://www.bnl.gov/rhic/

With only modest changes, these calculations also describe flow patterns seen in near-miss collisions, where photons that form a cloud around the speeding ions collide with the ions in the opposite beam.

“The upshot is that, using the same framework we use to describe lead-lead and proton-lead collisions, we can describe the data of these ultra-peripheral collisions where we have a photon colliding with a lead nucleus,” said Brookhaven Lab theorist Bjoern Schenke, a coauthor of the paper. “That tells you there’s a possibility that, in these photon-ion collisions, we create a small dense strongly interacting medium that is well described by hydrodynamics—just like in the larger systems.”

Fluid signatures

Observations of particles flowing in characteristic ways have been key evidence that the larger collision systems (lead-lead and proton-lead collisions at the LHC; and gold-gold and proton-gold collisions at RHIC) create a nearly perfect fluid. The flow patterns were thought to stem from the enormous pressure gradients created by the large number of strongly interacting particles produced where the colliding ions overlap.

“By smashing these high-energy nuclei together we’re creating such high energy density—compressing the kinetic energy of these guys into such a small space—that this stuff essentially behaves like a fluid,” Schenke said.

Spherical particles (including protons and nuclei) colliding head on are expected to generate a uniform pressure gradient. But partially overlapping collisions generate an oblong, almond-shaped pressure gradient that pushes more high-energy particles out along the short axis than perpendicular to it.

This “elliptic flow” pattern was one of the earliest hints that particle collisions at RHIC could create a quark-gluon plasma, or QGP—a hot soup of the fundamental building blocks that make up the protons and neutrons of nuclei/ions.

An image of the debris left over after the creation of a quark-gluon plasma in the collision of two nuclei at Brookhaven National Laboratory. Image courtesy of Brookhaven National Laboratory.

Scientists were at first surprised by the QGP’s liquid-like behavior. But they later established elliptic flow as a defining feature of QGP, and evidence that the quarks and gluons were still interacting strongly, even when free from confinement within individual protons and neutrons. Later observations of similar flow patterns in collisions of protons with large nuclei, intriguingly suggest that these proton-nucleus collision systems can also create tiny specks of quark-gluon soup.

“Our new paper is about pushing this to even further extremes, looking at collisions between photons and nuclei,” Schenke said.

Changing the projectile

It has long been known that that ultra-peripheral collisions could create photon-nucleus interactions, using the nuclei themselves as the source of the photons. That’s because charged particles accelerated to high energies, like the lead nuclei/ions accelerated at the LHC (and gold ions at RHIC), emit electromagnetic waves—particles of light. So, each accelerated lead ion at the LHC is essentially surrounded by a cloud of photons.

“When two of these ions pass each other very closely without colliding, you can think of one as emitting a photon, which then hits the lead ion going the other way,” Schenke said. “Those events happen a lot; it’s easier for the ions to barely miss than to precisely hit one another!”

This graphic shows the energy density at different times during the hydrodynamic evolution of the matter created in a collision of a lead nucleus (moving to the left) with a photon emitted from the other lead nucleus (moving to the right). Yellow represents the highest energy density and purple the lowest.

ATLAS scientists recently published data [Physical Review C (below)] on intriguing flow-like signals from these photon-nucleus collisions.

“We had to set up special data collection techniques to pick out these unique collisions,” said Blair Seidlitz, a Columbia University physicist who helped set up the ATLAS trigger system for the analysis when he was a graduate student at the University of Colorado-Boulder. “After collecting enough data, we were surprised to find flow-like signals that were similar to those observed in lead-lead and proton-lead collisions, although they were a little smaller.”

Schenke and his collaborators set out to see whether their theoretical calculations could accurately describe the particle flow patterns.

They used the same hydrodynamic calculations that describe the behavior of particles produced in lead-lead and proton-lead collision systems. But they made a few adjustments to account for the “projectile” striking the lead nucleus changing from a proton to a photon.

According to the laws of physics (specifically, quantum electrodynamics), a photon can undergo quantum fluctuations to become another particle with the same quantum numbers. A rho meson, a particle made of a particular combination of a quark and antiquark held together by gluons, is one of the most likely results of those photon fluctuations.

If you think back to the proton—made of three quarks—this two-quark rho particle is just a step down the complexity ladder.

“Instead of having a gluon distribution around three quarks inside a proton, we have the two quarks (quark-antiquark) with a gluon distribution around those to collide with the nucleus,” Schenke said.

Accounting for energy

The calculations also had to account for the big difference in energy in these photon-nucleus collision systems, compared to proton-lead and especially lead-lead.

“The emitted photon that’s colliding with the lead won’t carry the entire momentum of the lead nucleus it came from, but only a tiny fraction of that. So, the collision energy will be much lower,” Schenke said.

That energy difference turned out to be even more important than the change of projectile.

In the most energetic lead-lead or gold-gold heavy ion collisions, the pattern of particles emerging in the plane transverse to the colliding beams generally persists no matter how far you look from the collision point along the beamline (in the longitudinal direction). But when Schenke and collaborators modeled the patterns of particles expected to emerge from lower-energy photon-lead collisions, it became apparent that including the 3D details of the longitudinal direction made a difference. The model showed that the geometry of the particle distributions changes rapidly with increasing longitudinal distance; the particles become “decorrelated.”

“The particles see different pressure gradients depending on their longitudinal position,” Schenke explained.

“So, for these low energy photon-lead collisions, it is important to run a full 3D hydrodynamic model (which is more computationally demanding) because the particle distribution changes more rapidly as you go out in the longitudinal direction,” he said.

When the theorists compared their predictions using this lower-energy, full 3D, hydrodynamic model with the particle flow patterns observed in photon-lead collisions by the ATLAS detector, the data and theory matched up nicely, at least for the most obvious elliptic flow pattern, Schenke said.

Implications and the future

“From this result, it looks like it’s conceivable that, even in photon-heavy ion collisions, we have a strongly interacting fluid that responds to the initial collision geometry, as described by hydrodynamics,” Schenke said. “If the energies and temperatures are high enough,” he added, “there will be a quark-gluon plasma.”

Seidlitz, the ATLAS physicist, commented, “It was very interesting to see these results suggesting the formation of a small droplet of quark-gluon plasma, as well as how this theoretical analysis offers concrete explanations as to why the flow signatures are a bit smaller in photon-lead collisions.”

Additional data to be collected by ATLAS and other experiments at RHIC and the LHC over the next several years will enable more detailed analyses of particles flowing from photon-nucleus collisions. These analyses will help distinguish the hydrodynamic calculation from another possible explanation, in which the flow patterns are not a result of the system’s response to the initial geometry.

In the longer-term future, experiments at an Electron-Ion Collider (EIC) [below], a facility planned to replace RHIC sometime in the next decade at Brookhaven Lab, could provide more definitive conclusions.

Schenke’s theoretical work was funded by the DOE Office of Science (NP). Operations at RHIC, a DOE Office of Science user facility, and planning for the future EIC are also funded by the Office of Science. Brookhaven Lab physicists play many roles in the ATLAS experiment, also funded by the Office of Science (HEP and NP) and the National Science Foundation.

Science papers:
Physical Review Letters
Physical Review C
If you have credentials, see the science papers for instructive material with images.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC].

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL RHIC’s newly enhanced STAR detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

From The DOE’s Brookhaven National Laboratory: “Nuclear Theorists Collaborate to Explore ‘Heavy Flavor’ Particles”

From The DOE’s Brookhaven National Laboratory

12.7.22
Karen McNulty Walsh
kmcnulty@bnl.gov
(631) 344-8350

Peter Genzer
genzer@bnl.gov
(631) 344-3174

Leading U.S. researchers will develop framework for describing exotic particles’ behavior at various stages in the evolution of hot nuclear matter.

Tracking Heavy Quarks Collisions at the Relativistic Heavy Ion Collider (RHIC) produce a hot soup of quarks and gluons (center)—and ultimately thousands of new particles. A new theory collaboration seeks to understand how heavy quarks (Q) and antiquarks (Q-bar) interact with this quark-gluon plasma (QGP) and transform into composite particles that strike the detector. Tracking these “heavy flavor” particles can help scientists unravel the underlying microscopic processes that drive the properties of the QGP.

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory will participate in a new Topical Theory Collaboration funded by DOE’s Office of Nuclear Physics to explore the behavior of so-called “heavy flavor” particles. These particles are made of quarks of the “charm” and “bottom” varieties, which are heavier and rarer than the “up” and “down” quarks that make up the protons and neutrons of ordinary atomic nuclei. By understanding how these exotic particles form, evolve, and interact with the medium created during powerful particle collisions, scientists will gain a deeper understanding of a unique form of matter known as a quark-gluon plasma (QGP) that filled the early universe.

These experiments take place at the Relativistic Heavy Ion Collider (RHIC)[below] at Brookhaven Lab and the Large Hadron Collider (LHC) at Europe’s CERN laboratory [below]. Scientists accelerate and smash together the nuclei of heavy atoms at energies high enough to set free the quarks and gluelike “gluons” that hold ordinary matter together. These collisions create a soup of quarks and gluons much like the matter that existed just after the Big Bang, some 14 billion years ago.

A powerful theory, known as quantum chromodynamics (QCD), describes very accurately how the plasma’s quarks and gluons interact. But understanding how those fundamental interactions lead to the complex characteristics of the plasma—a trillion-degree, dense medium that flows like a fluid with no resistance—remains a great challenge in modern research.

The Heavy-Flavor Theory (HEFTY) for QCD Matter Topical Theory Collaboration, which will be led by Ralf Rapp from Texas A&M University, seeks to close that gap in understanding by developing a rigorous and comprehensive theoretical framework for describing how heavy-flavor particles interact with the QGP.

“With a heavy-flavor framework in place, experiments tracking these particles can be used to precisely probe the plasma’s properties,” said Peter Petreczky, a theorist at Brookhaven Lab, who will serve as co-spokesperson for the collaboration along with Ramona Vogt from The DOE’s Lawrence Livermore National Laboratory. “Our framework will also provide a foundation for using heavy-flavor particles as a probe at the future Electron-Ion Collider (EIC) [below]. Future experiments at the EIC will probe different forms of cold nuclear matter which are the precursors of the QGP in the laboratory,” Petreczky said.

In heavy ion collisions at RHIC and the LHC, heavy charm and bottom quarks are produced upon initial impact of the colliding nuclei. Their large masses cause a diffusive motion that can serve as a marker of the interactions in the QGP, including the fundamental process of quarks binding together to form composite particles called hadrons.

“The framework needs to describe these particles from their initial production when the nuclei first collide, through their subsequent diffusion through the QGP and hadroniziation,” Petreczky said. “And these descriptions need to be embedded into realistic numerical simulations that enable quantitative comparisons to experimental data.”

Swagato Mukherjee of Brookhaven Lab will be a co-principal investigator in the collaboration, responsible for lattice QCD computations. These calculations require some of the world’s most powerful supercomputers to handle the complex array of variables involved in quark-gluon interactions.

“Recently there has been significant progress in lattice QCD calculations related to heavy flavor probes of QGP,” Mukherjee said. “We are in an exciting time when the exascale computing facilities and the support provided by the topical collaboration will enable us to perform realistic calculations of the key quantities needed for theoretical interpretation of experimental results on heavy flavor probes.”

In addition to lattice QCD the collaboration will use variety of theoretical approaches, including rigorous statistical data analysis to obtain the transport properties of QGP.

“The resulting framework will help us unravel the underlying microscopic processes that drive the properties of the QGP, thereby providing unprecedented insights into the inner workings of nuclear matter based on QCD,” said Rapp of Texas A&M, the principal investigator of the project.

The HEFTY collaboration will receive $2.5 Million from the DOE Office of Science, Office of Nuclear Physics, over five years. That funding will provide partial support for six graduate students and three postdoctoral fellows at 10 institutions, as well as a senior staff position at one of the national laboratories. It will also establish a bridge junior faculty position at Kent State University.

Partnering institutions include Brookhaven National Laboratory, Duke University, Florida State University, Kent State University, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Massachusetts Institute of Technology, Texas A&M University, and The DOE’s Thomas Jefferson National Accelerator Facility.

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Brookhaven Campus

One of ten national laboratories overseen and primarily funded by the The DOE Office of Science, The DOE’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world. Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.

Research at BNL specializes in nuclear and high energy physics, energy science and technology, environmental and bioscience, nanoscience and national security. The 5300 acre campus contains several large research facilities, including the Relativistic Heavy Ion Collider [below] and National Synchrotron Light Source II [below]. Seven Nobel prizes have been awarded for work conducted at Brookhaven lab.

BNL is staffed by approximately 2,750 scientists, engineers, technicians, and support personnel, and hosts 4,000 guest investigators every year. The laboratory has its own police station, fire department, and ZIP code (11973). In total, the lab spans a 5,265-acre (21 km^2) area that is mostly coterminous with the hamlet of Upton, New York. BNL is served by a rail spur operated as-needed by the New York and Atlantic Railway. Co-located with the laboratory is the Upton, New York, forecast office of the National Weather Service.

Major programs

Although originally conceived as a nuclear research facility, Brookhaven Lab’s mission has greatly expanded. Its foci are now:

Nuclear and high-energy physics
Physics and chemistry of materials
Environmental and climate research
Nanomaterials
Energy research
Nonproliferation
Structural biology
Accelerator physics

Operation

Brookhaven National Lab was originally owned by the Atomic Energy Commission and is now owned by that agency’s successor, the United States Department of Energy (DOE). DOE subcontracts the research and operation to universities and research organizations. It is currently operated by Brookhaven Science Associates LLC, which is an equal partnership of Stony Brook University and Battelle Memorial Institute. From 1947 to 1998, it was operated by Associated Universities, Inc. (AUI), but AUI lost its contract in the wake of two incidents: a 1994 fire at the facility’s high-beam flux reactor that exposed several workers to radiation and reports in 1997 of a tritium leak into the groundwater of the Long Island Central Pine Barrens on which the facility sits.

Foundations

Following World War II, the US Atomic Energy Commission was created to support government-sponsored peacetime research on atomic energy. The effort to build a nuclear reactor in the American northeast was fostered largely by physicists Isidor Isaac Rabi and Norman Foster Ramsey Jr., who during the war witnessed many of their colleagues at Columbia University leave for new remote research sites following the departure of the Manhattan Project from its campus. Their effort to house this reactor near New York City was rivalled by a similar effort at the Massachusetts Institute of Technology to have a facility near Boston, Massachusetts. Involvement was quickly solicited from representatives of northeastern universities to the south and west of New York City such that this city would be at their geographic center. In March 1946 a nonprofit corporation was established that consisted of representatives from nine major research universities — Columbia University, Cornell University, Harvard University, Johns Hopkins University, Massachusetts Institute of Technology, Princeton University, University of Pennsylvania, University of Rochester, and Yale University.

Out of 17 considered sites in the Boston-Washington corridor, Camp Upton on Long Island was eventually chosen as the most suitable in consideration of space, transportation, and availability. The camp had been a training center from the US Army during both World War I and World War II. After the latter war, Camp Upton was deemed no longer necessary and became available for reuse. A plan was conceived to convert the military camp into a research facility.

On March 21, 1947, the Camp Upton site was officially transferred from the U.S. War Department to the new U.S. Atomic Energy Commission (AEC), predecessor to the U.S. Department of Energy (DOE).

Research and facilities

Reactor history

In 1947 construction began on the first nuclear reactor at Brookhaven, the Brookhaven Graphite Research Reactor. This reactor, which opened in 1950, was the first reactor to be constructed in the United States after World War II. The High Flux Beam Reactor operated from 1965 to 1999. In 1959 Brookhaven built the first US reactor specifically tailored to medical research, the Brookhaven Medical Research Reactor, which operated until 2000.

Accelerator history

In 1952 Brookhaven began using its first particle accelerator, the Cosmotron. At the time the Cosmotron was the world’s highest energy accelerator, being the first to impart more than 1 GeV of energy to a particle.

BNL Cosmotron 1952-1966.

The Cosmotron was retired in 1966, after it was superseded in 1960 by the new Alternating Gradient Synchrotron (AGS).

BNL Alternating Gradient Synchrotron (AGS).

The AGS was used in research that resulted in 3 Nobel prizes, including the discovery of the muon neutrino, the charm quark, and CP violation.

In 1970 in BNL started the ISABELLE project to develop and build two proton intersecting storage rings.

The groundbreaking for the project was in October 1978. In 1981, with the tunnel for the accelerator already excavated, problems with the superconducting magnets needed for the ISABELLE accelerator brought the project to a halt, and the project was eventually cancelled in 1983.

The National Synchrotron Light Source operated from 1982 to 2014 and was involved with two Nobel Prize-winning discoveries. It has since been replaced by the National Synchrotron Light Source II. [below].

BNL National Synchrotron Light Source.

After ISABELLE’S cancellation, physicist at BNL proposed that the excavated tunnel and parts of the magnet assembly be used in another accelerator. In 1984 the first proposal for the accelerator now known as the Relativistic Heavy Ion Collider (RHIC)[below] was put forward. The construction got funded in 1991 and RHIC has been operational since 2000. One of the world’s only two operating heavy-ion colliders, RHIC is as of 2010 the second-highest-energy collider after the Large Hadron Collider (CH). RHIC is housed in a tunnel 2.4 miles (3.9 km) long and is visible from space.

On January 9, 2020, it was announced by Paul Dabbar, undersecretary of the US Department of Energy Office of Science, that the BNL eRHIC design has been selected over the conceptual design put forward by DOE’s Thomas Jefferson National Accelerator Facility [Jlab] as the future Electron–ion collider (EIC) in the United States.

Electron-Ion Collider (EIC) at DOE’s Brookhaven National Laboratory to be built inside the tunnel that currently houses the Relativistic Heavy Ion Collider [RHIC].

In addition to the site selection, it was announced that the BNL EIC had acquired CD-0 from the Department of Energy. BNL’s eRHIC design proposes upgrading the existing Relativistic Heavy Ion Collider, which collides beams light to heavy ions including polarized protons, with a polarized electron facility, to be housed in the same tunnel.

Other discoveries

In 1958, Brookhaven scientists created one of the world’s first video games, Tennis for Two. In 1968 Brookhaven scientists patented Maglev, a transportation technology that utilizes magnetic levitation.

Major facilities

Relativistic Heavy Ion Collider (RHIC), which was designed to research quark–gluon plasma and the sources of proton spin. Until 2009 it was the world’s most powerful heavy ion collider. It is the only collider of spin-polarized protons.

Center for Functional Nanomaterials (CFN), used for the study of nanoscale materials.

BNL National Synchrotron Light Source II, Brookhaven’s newest user facility, opened in 2015 to replace the National Synchrotron Light Source (NSLS), which had operated for 30 years. NSLS was involved in the work that won the 2003 and 2009 Nobel Prize in Chemistry.

Alternating Gradient Synchrotron, a particle accelerator that was used in three of the lab’s Nobel prizes.
Accelerator Test Facility, generates, accelerates and monitors particle beams.
Tandem Van de Graaff, once the world’s largest electrostatic accelerator.

Computational Science resources, including access to a massively parallel Blue Gene series supercomputer that is among the fastest in the world for scientific research, run jointly by Brookhaven National Laboratory and Stony Brook University-SUNY.

Interdisciplinary Science Building, with unique laboratories for studying high-temperature superconductors and other materials important for addressing energy challenges.
NASA Space Radiation Laboratory, where scientists use beams of ions to simulate cosmic rays and assess the risks of space radiation to human space travelers and equipment.

Off-site contributions

It is a contributing partner to the ATLAS experiment, one of the four detectors located at the The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Large Hadron Collider(LHC).

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

Iconic view of the European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] ATLAS detector.

It is currently operating at The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] near Geneva, Switzerland.

Brookhaven was also responsible for the design of the Spallation Neutron Source at DOE’s Oak Ridge National Laboratory, Tennessee.

DOE’s Oak Ridge National Laboratory Spallation Neutron Source annotated.

Brookhaven plays a role in a range of neutrino research projects around the world, including the Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China.

Daya Bay Neutrino Experiment (CN) nuclear power plant, approximately 52 kilometers northeast of Hong Kong and 45 kilometers east of Shenzhen, China .

DOE’s Fermi National Accelerator Laboratory DUNE LBNF from FNAL to Sanford Underground Research Facility, Lead, South Dakota.

BNL Center for Functional Nanomaterials.

BNL National Synchrotron Light Source II.

BNL NSLS II.

BNL Relative Heavy Ion Collider Campus.

BNL RHIC’s newly enhanced STAR detector.

BNL/RHIC Phenix detector.

Brookhaven sPhenix Assembly

BNL RHIC Schematic view of the proposed sPHENIX detector.

BNL RHIC inner hadronic calorimeter being installed in the sPHENIX Detector.

From CERN [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH): “LHC Report – The switch was flipped and the beams were dumped”

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

From CERN [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)

12.7.22
Rende Steerenberg

On Monday, 28 November at 6 o’clock in the morning, the LHC Engineer in Charge flipped the switch and the last proton beams of 2022 made a final turn around the LHC before being discarded into the dedicated beam dumps. This marked the end of the first of four years of Run 3 and the start of the year-end technical stop (YETS), a mere 21 weeks after the very first collision at 6.8 TeV per beam.

2022 was, without a doubt, a commissioning year: our teams encountered problems related to Long Shutdown 2 (LS2) updates, as well as beam intensity limitations due to heat load, in particular in sector 7-8. Thankfully, these issues were effectively addressed, and alternative beam schemes were tested and used to overcome the limitations.

All in all, the machine and beam performance exceeded initial expectations. The integrated luminosity prediction for 2022 was 25 fb^-1, based on a beam availability factor of 30%, which matches average values for commissioning years. In fact, the beam availability factor for a major part of the physics run was closer to 50%, despite two extended stops in May and August–September and the longer YETS, which was brought forward by two weeks due to the worldwide energy crisis. Along with the good beam performance, this availability resulted in the delivery of 40 fb-1 for both ATLAS and CMS. However, the four-week lead run, which was scheduled at the end of the year, was cancelled in favor of proton physics.

The LHC would not have achieved this impressive number of collisions without the considerable flexibility and good performance of the injector complex, which concluded its second year of Run 3 (already!) on 28 November 2022. The injectors are reaping the benefits of the LHC Injector Upgrade undertaken during LS2, and the intensity ramp-up towards HL-LHC beam parameters has made commendable progress over the past few months – the PS and its Booster have actually reached these parameters already in 2022.

Besides feeding protons to the LHC, the injectors have once again served the rich and varied fixed-target physics programmes of ISOLDE [below], the East Area, the n_TOF facility [below], the Antiproton factory [below], AWAKE [below], HiRadMat [below] and the North Area. As an example, the SPS [below] provided a record 2.3×10^19 protons to the North Area while improving the quality of the beam spill, as requested by the users.

Left: The integrated number of protons sent to the North Area in the years 2017–2022. Right: The weekly number of protons sent to the North Area, with a record during summer 2022. (Courtesy of K. Li)

Although the lead ion run was cancelled at the LHC, lead ions were successfully fed to the North Area for a two-week physics run, down from four weeks. In addition, the commissioning of the slip-stacked LHC ion beam in the SPS was completed, and LHC experiments did register some lead–lead collisions as part of a two-day lead ion test run in November, during which slip-stacked bunches were injected.

Today, instead of particles, technicians and engineers are whizzing around the tunnels to ensure that the accelerator complex is properly maintained, and to prepare it for 2023 – another year of hopefully efficient operation and promising data taking.

See the full article here.

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings
Please help promote STEM in your local schools.

Stem Education Coalition

Meet CERN in a variety of places:

Quantum Diaries

Cern Courier

The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator. (Image: Julien Ordan/CERN).

THE FOUR MAJOR PROJECT COLLABORATIONS

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ATLAS another view Image Claudia Marcelloni ATLAS CERN.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALICE.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CMS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] LHCb.

LHC

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

CERN Large Electron Positron Collider

3D cut of the LHC dipole CERN LHC underground tunnel and tube.

The LHC magnets surround the beampipe along its 27 km circumference- Image CERN

CERN SixTrack LHC particles.

OTHER PROJECTS AT CERN

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AEGIS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALPHA Antimatter Factory.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ALPHA-g Detector.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AMS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ASACUSA.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear] [ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ATRAP.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Antiproton Decelerator.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] AWAKE.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] BASE: Baryon Antibaryon Symmetry Experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] BASE instrument.

The European Organization for Nuclear Research [Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN] [CERN] BASE: Baryon Antibaryon Symmetry Experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CAST Axion Solar Telescope.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CLOUD.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] COMPASS.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] CRIS experiment.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] DIRAC.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] FASER experiment schematic.

CERN FASER is designed to study the interactions of high-energy neutrinos and search for new as-yet-undiscovered light and weakly interacting particles. Such particles are dominantly produced along the beam collision axis and may be long-lived particles, travelling hundreds of metres before decaying. The existence of such new particles is predicted by many models beyond the Standard Model that attempt to solve some of the biggest puzzles in physics, such as the nature of dark matter and the origin of neutrino masses.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] GBAR.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ISOLDE Looking down into the ISOLDE experimental hall.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] LHCf.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] The MoEDAL experiment- a new light on the high-energy frontier.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] NA62.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] NA64.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] n_TOF.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] TOTEM.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] UA9.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] The SPS’s new RF system.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] Proto Dune.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][ Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] HiRadMat-High Radiation to Materials.

The SND@LHC experiment consists of an emulsion/tungsten target for neutrinos (yellow) interleaved with electronic tracking devices (grey), followed downstream by a detector (brown) to identify muons and measure the energy of the neutrinos. (Image: Antonio Crupano/SND@LHC)

From “Symmetry”: “First-time ATLAS measurement provides new look at Higgs”

From “Symmetry”

DOE’s Fermi National Accelerator Laboratory Wilson Hall.

DOE’s SLAC National Accelerator Laboratory campus with world’s first x-ray laser- the Linac Coherent Light Source (LCLS) unveiled in 2009.

11.29.22
Madeleine O’Keefe

Event display depicting a particle collision in the ATLAS detector. Credit: ATLAS Collaboration.

For the first time physicists have a statistically significant measurement of the joint polarization of W and Z bosons.

W an Z bosons in Feynman diagram. Wikipedia.

Luka Selem says he was always a curious kid. Growing up in France, he was given copies of Science et vie junior, a science magazine for young people, by his parents.

“Since I was very young, I was always interested in quite a lot of things,” he says. “I was always asking, ‘Why? But why that? Why that, and then why that?’ I wanted to go all the way to the end. I was never satisfied by the answer.”

Particle physics, the study of the fundamental particles and forces that make up everything around us, turned out to be a good way for Selem to search for answers. “In particle physics, there is no other ‘why,’” he says. “No one can tell me the rest of the story. I have to find it myself with my colleagues.”

Selem recently found a new way to search for the rest of the story while doing research for his doctoral thesis. With other physicists on the ATLAS experiment at Europe’s CERN laboratory, Selem successfully made a measurement of particles called W and Z bosons that will allow physicists to further probe the mechanism that grants particles mass.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] ATLAS another view Image Claudia Marcelloni ATLAS CERN.

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH) [CERN].

3D cut of the LHC dipole CERN LHC underground tunnel and tube

The LHC magnets surround the beampipe along its 27 km circumference- Image CERN

The European Organization for Nuclear Research [La Organización Europea para la Investigación Nuclear][Organization européenne pour la recherche nucléaire] [Europäische Organization für Kernforschung](CH)[CERN] map.

SixTRack CERN LHC particles.

How the boson got its polarization

Bosons are a category of subatomic particles that are associated with the four fundamental forces in the universe: gravity, electromagnetism, the strong nuclear force and the weak nuclear force. The most familiar boson is the photon, the force carrier of light, that is responsible for electromagnetism. 

While photons are massless, massive bosons, such as the W and Z bosons, have properties that set them apart from other particles. One concerns their polarization, the degree by which the quantum spin of the boson is aligned in a given direction. A boson can be transversely or longitudinally polarized. (There are technically two types of transverse polarization—left and right—but they are not yet differentiable in the data for joint polarizations of two bosons.) Massive bosons can be longitudinally polarized, meaning that their spin can be oriented perpendicular to their direction of motion.

“Among physicists, polarization is something … you’re not sure you understand exactly what it is,” says Selem, who admits he was not very familiar with polarization himself when he chose his PhD project at Laboratoire d’Annecy de Physique des Particules, or LAPP.

The W and Z bosons enable the weak force, the force responsible for radioactive decay, the same way that photons enable the electromagnetic force. But, unlike photons, W and Z bosons have mass, thanks to their interactions with a field generated by yet another boson, the Higgs.

Higgs in Standard Model of Particle Physics

Fundamental particles’ interactions with the Higgs field are what physicists believe generate mass. 

This is what makes polarization so interesting. “It’s a very indirect way of probing the Higgs mechanism,” says Selem.

W and Z bosons gain mass in a process called electroweak symmetry breaking. When symmetry “breaks,” four particles are created, including the Higgs boson, says Junjie Zhu, a professor at the University of Michigan and an ATLAS physicist. 

The other three particles are incorporated into the W+, W- and Z bosons, giving them mass and granting them a new longitudinal polarization. “[It is] very important to study the longitudinal components of the W and Z bosons because the longitudinal components are originally from the symmetry breaking,” says Zhu.

This provides a unique window through which to search for new physics—things that can’t be explained by the current Standard Model of particle physics. Physicists want to measure longitudinal joint polarization more accurately because new physics is “often sensitive to longitudinal components,” says Zhu. 

Since the 1990s era of the Large Electron-Positron Collider—the predecessor to the Large Hadron Collider at CERN—polarizations of W and Z bosons have been studied individually. But studies of single boson polarization measurements have not revealed any hints of new physics. 

To keep probing the Standard Model, then, physicists next sought to measure joint polarization: two bosons polarized simultaneously. If the value they measured deviated from the Standard Model prediction, it would be an indicator of new physics, like an unknown aspect of the Higgs mechanism.

A new measurement

Selem and his colleagues used ATLAS data taken between 2015 and 2018 during Run 2 of the Large Hadron Collider. The researchers aligned these data with templates based on theoretical predictions for the four different combinations of polarizations. 

“We have different [templates] from the simulations that tell us what shapes look like for longitudinal-longitudinal, transversal-transversal, longitudinal-transversal and transversal-longitudinal,” says Zhu, who does similar analyses with ATLAS.

The physicists scaled their four templates to match the histogram of data. The proportion of each template in the end revealed the fraction of W and Z bosons with the respective joint polarizations. In the analysis, they found that the longitudinal-longitudinal fraction was statistically significant.

The results support the model of the universe as we know it. “With the present sensitivity, no sign of new physics was observed, pushing even further the domain of validity of the Standard Model,” says Emmanuel Sauvan, an ATLAS physicist at LAPP and Selem’s PhD advisor. “This is per se an interesting result, even if I would have preferred myself to see new physics effects.

Standard Model of Particle Physics, Quantum Diaries.

“One next step is to refine this measurement, in view of reducing its uncertainties, with more data that we are recording right now [during LHC Run 3].”

An important step further in the future will be to measure the scattering of two longitudinally polarized bosons. This interaction is even more sensitive to new physics, but researchers need 10–20 times more data than they have now to hope to detect this event. 

“Such polarization measurements in vector boson scattering will require much more luminosity, and we will have to wait for the High-Luminosity LHC,” says Sauvan, referring to the proposed upgrade of the Large Hadron Collider scheduled for the late 2020s. “It will allow us to fully validate the Higgs mechanism of the Standard Model.”

For now, the joint polarization result is a significant development. The researchers overcame challenges that had limited previous experiments’ attempts at the measurement, and they developed new analysis techniques, including machine learning algorithms. 

Prachi Atmasiddha, a graduate student at the University of Michigan working with Zhu, performed event generation for the joint polarization result. “Once we had those events, that was one of the very important [reasons] why this analysis was motivated,” she says. “We [determined that we] can produce these separately polarized events, so we can build models on that, and we can do fitting with these templates of different polarization states.”

Selem says he looks forward to finding out what physicists are able to do next. “I would say the most important part of this measurement is the roadmap it provides to do further measurements, because we did meet a lot of challenges that will happen in other similar measurements, and we gave ideas on how to solve them.”

Selem recently accepted a postdoctoral research position in Grenoble, France, where he will work on detector development and exotic searches. There, he and his fellow physicists will continue to seek their own answers to the question, “Why?”

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”.

five-ways-keep-your-child-safe-school-shootings

Please help promote STEM in your local schools.

Stem Education Coalition

Symmetry is a joint Fermilab/SLAC publication.