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  • richardmitnick 11:47 am on October 17, 2016 Permalink | Reply
    Tags: , CERN ATLAS, , Dr Michel Della Negra, Dr Peter Jenni, , Sir Tejinder (Jim) Virdee, W.K.H. Panofsky Prize   

    From ICL: “Fathers of Higgs boson detectors awarded particle physics prize” 

    Imperial College London
    Imperial College London

    17 October 2016
    Hayley Dunning

    1
    Professor Sir Tejinder Virdee (L) and Dr Michel DellaNegra (R)

    2
    Dr Peter Jenni

    Two Imperial physicists share in a prize for experimental physics for their work masterminding the CMS and ATLAS experiments

    The W.K.H. Panofsky Prize in Experimental Particle Physics, awarded by the American Physical Society, has this year been given to three scientists, “For distinguished leadership in the conception, design, and construction of the ATLAS and CMS detectors, which were instrumental in the discovery of the Higgs boson.”

    Receiving the honours are Professor Sir Tejinder (Jim) Virdee FRS from the Department of Physics at Imperial, Dr Michel Della Negra from CERN, who is also a Distinguished Research Fellow at Imperial, and Dr Peter Jenni from CERN and Albert-Ludwigs-University Freiburg.

    In July 2012, scientists using the Compact Muon Solenoid (CMS) and A Toroidal LHC Apparatus (ATLAS) experiments operating at the Large Hadron Collider (LHC) at CERN announced the discovery of the Higgs boson.

    CERN/CMS Detector
    CERN/CMS Detector

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN/ATLAS detector
    CERN/ATLAS detector

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    This new particle, whose associated field gives mass to the fundamental particles, is the last missing link of the Standard Model of particle physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth

    Professor Jordan Nash, head of the Department of Physics at Imperial, said: “I’m delighted to see that Jim and Michel have been awarded this year’s Panofsky prize. Their dedication for more than two decades to the design, construction, and operation of the CMS detector has been essential to enabling the wonderful science and discoveries we have seen at the LHC.”

    Hayley Dunning talked to Professor Virdee about his latest award, chasing the Higgs and the future of the Large Hadron Collider.

    You’ve won a few prizes for your work – how does it feel to win the W.K.H. Panofsky Prize?

    It is a great honour to receive this prize and it is particularly pleasing to get this recognition from our peers. Even though the past 25 years have been long and not without many difficulties, it has nevertheless led to a fantastic result for all of us at the LHC – the discovery of the Higgs boson.

    This award is also acknowledgement of the huge experimental effort that led to the discovery of the Higgs boson. This wouldn’t have been possible without the contributions of thousands of scientists and engineers from around the world. On a personal note, I have enjoyed the enormous support of my exceptional colleagues at Imperial as well as the many others in the CMS Collaboration.

    What attracted you to particle physics and big experiments like the LHC?

    Particle physics is a modern-day name for the centuries-old effort to understand the fundamental laws of nature. I was intrigued to find out more: how nature really works at the most fundamental level, and I’ve always felt that this has to be one of the most exciting of human endeavours.

    Particle physicists didn’t really set out to do ‘big’ experiments. I, like my colleagues, were not attracted by the magnitude of the experiment, but by the magnitude and importance of the questions for which we were searching answers. CMS has the size it has due to the huge power of its ‘microscope’ to examine physics at the smallest distance scales offered for study by the highest accelerator energy so far achieved.

    And this can be seen in the history of this endeavour: twenty-five years ago, we started CMS with a handful of physicists and engineers. The enormity of the detectors that were necessary to answer these enormous questions meant that the collective talents and resources of a worldwide effort would be necessary. Now, CMS has over 3,000 scientists and engineers and involves 40 countries.

    Did you always believe you would be able to find the Higgs boson with CMS and ATLAS?

    In retrospect, and not overlooking the open mind that we all physicists have to have, I did believe, that if the Higgs boson were a true constituent particle of nature, we would find it sooner or later at the LHC. It has to be remembered that mass is a fundamental attribute of fundamental particles and is what gives our universe substance.

    At the time of conception of the CMS detector, a few of us paid particular attention to conjectures that suggested the mass of the Higgs boson could lie in the range where, years later, in 2012, it was eventually found. In this range the electromagnetic calorimeter, which I pioneered, played a vital role. Similarly, other parts of CMS were conceived, designed and constructed so as to ensure that the Higgs boson would be found if it were at other masses.

    Luckily, it turned out that the Higgs boson is a choice of nature. What was less of a stroke of luck is that we found it – given that it is a real element of nature.

    What are you working on now, and what do you hope for the future of the LHC experiments?

    My current work involves the in-depth study of the properties of the newly found Higgs boson, the search for widely anticipated physics beyond the Standard Model, and the design of the upgrades to the CMS detector for very high luminosity (implying very high proton-proton interaction rate) LHC running, due to start in the mid-2020s.

    In the context of this upgrade, a year or so ago I began another exciting project to develop a novel technique to replace a part of CMS. The goal is to increase the physics reach of the next phase of the LHC and take us into the 2030s. In 2015 I was awarded an EU-ERC Advanced grant to carry out the research, development and prototyping of this novel project.

    See the full article here .

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    Imperial College London

    Imperial College London is a science-based university with an international reputation for excellence in teaching and research. Consistently rated amongst the world’s best universities, Imperial is committed to developing the next generation of researchers, scientists and academics through collaboration across disciplines. Located in the heart of London, Imperial is a multidisciplinary space for education, research, translation and commercialisation, harnessing science and innovation to tackle global challenges.

     
  • richardmitnick 8:46 am on October 13, 2016 Permalink | Reply
    Tags: , , CERN ATLAS, , ,   

    From Harvard: “They ponder the universe” 

    Harvard University

    Harvard University

    October 12, 2016
    Alvin Powell

    Harvard students join faculty at CERN in Europe to tackle physics’ mysteries


    Access mp4 video here .

    Once you know enough math, Harvard Ph.D. student Tony Tong said, you get to know physics. And physics, he said, is simply amazing.

    “[Physics] is always helpful to answer the question of ‘Why?’ Why the skies are blue, why the universe is so big, basic stuff,” Tong said. “I’m always curious about those questions and the solution is always so beautiful.”

    Tong, it seems, had come to the right place. He was speaking on a warm July day in a small courtyard at the European Organization for Nuclear Research, known as CERN, the scientific campus on the outskirts of Geneva that is the world’s beating heart for high-energy particle physics.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC at CERN

    Home of the world’s most powerful particle accelerator, the Large Hadron Collider (LHC), CERN made world headlines in 2012 when scientists announced the discovery of the Higgs boson, the final undiscovered particle in the theoretical framework of the universe called the Standard Model.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    The eyes of the scientific world remain focused on CERN today because the LHC is back in operation after a major upgrade that boosted its energy to 13 tera electron volts, allowing it to crash beams of protons into each other more powerfully than ever before. Now that the Standard Model is complete, scientists are looking for what’s still mysterious, sometimes called the “new physics” or “physics beyond the Standard Model.” Its form, presumably, would involve a particle born of these high-energy collisions, one that points the way to an even broader understanding of the universe, shedding light on such puzzling areas as dark matter, supersymmetry, dark energy, and even gravity, which has stubbornly refused to fit neatly into our understanding of the universe’s basic forces.

    Standard model of Supersymmetry DESY
    Standard model of Supersymmetry DESY

    CERN fired up its first accelerator in 1957. Among its milestone discoveries are the elementary particles called W and Z bosons, antihydrogen — the antimatter version of the common element — and the creation of the World Wide Web to share massive amounts of information among scientists, scattered at institutions around the world.

    The CERN campus, which straddles the Switzerland-France border amid breathtaking views of the distant Alps, produces more than just science, however. In ways technological, theoretical, educational, and inspirational, it also produces scientists.


    Access mp4 video here .
    Inside the Antimatter Factory at CERN, the ATRAP antimatter experiment seeks to slow and trap antimatter for comparison with ordinary matter.

    CERN ATRAP New
    CERN ATRAP

    “Those four years at CERN doing research were a very important part of my training,” said Harvard Physics Department chair Masahiro Morii, who was a research scientist at CERN early in his career. “It taught me things that are a bit difficult to quantify, but changed my perspective very drastically on what it means to be a scientist, what it means to be a high-energy physicist.”

    Year-round, the graduate students and postdoctoral fellows taking their initial career steps work among established scientists, learning and gaining experience difficult to get outside of CERN or a handful of other facilities around the world. Harvard’s Donner Professor of Science John Huth said what becomes apparent is science’s messiness.

    “They see the process as it unfold with all its warts. Science is pretty messy when you get into the nitty-gritty,” Huth said. “It’s just an invaluable experience. Even if you become a scientist in a different discipline or you leave science entirely, understanding that intrinsic messiness is really important.”

    In an environment focused on the practice of physics rather than the teaching of it, CERN puts the onus for learning onto the student, Morii said. Students build and test equipment, make sure what’s installed is running properly, and pluck the most meaningful pieces from the resulting data tsunami. They analyze it at all hours of the day and sometimes deep into the night, since there’s always someone awake and logged onto Skype to answer a question or share an insight.

    “People are really passionate, so it doesn’t really feel like you’re up until 11 doing your job. Maybe you’re thinking about something on the train home and you wanted to look into it. It’s not regular hours, but I don’t think that deters anyone,” said Harvard physics Ph.D. student Julia Gonski. “People like the work and it’s fun. Twenty-four hours a day, you can get on Skype and someone you know is on Skype and working.”

    While fellows and graduate students are at CERN year-round, each summer the campus’ population swells as undergraduates eager to take part in the world’s most famous science experiment step off the plane in Geneva.

    At CERN, they become part of a unique city of physicists from around the world, with different educational and cultural backgrounds but the same passions and similar goals.

    “It was this enormous scientific laboratory, with thousands of people working all hours of the night trying to understand the fundamentals of the universe, as corny as that is to say,” said Harvard postdoctoral fellow Alexander Tuna, who first came to CERN as a summer undergrad from Duke University in 2009. “It was really immersive and fun. There’s always someone around with an interesting insight or an answer to a question.”

    The secrets of the universe

    As a visitor approaches CERN, the giant brown orb of the multistory Globe of Science and Innovation comes into view.

    The globe, looking like an enormous particle half-buried in the earth, serves as a CERN welcome center and is far more visually appealing than the main campus across the street. Protected by fences with access limited through guard stations, the campus’ narrow, twisting roadways wind between boxy, industrial-looking buildings numbered instead of named, as if creativity there is reserved for science instead of infrastructure. Even the cafeteria that serves as a central gathering spot is named simply “Restaurant 1.”

    “It was different than I expected,” said Harvard junior Matthew Bledsoe. “I figured a place on the forefront of physics would look fresher and newer, new buildings and stuff. But [they are] 1950s and ’60s-era buildings, so the buildings are pretty old. It looks like a factory.”

    Visitors quickly learn to look past the boxy exteriors to what’s inside. There they find thousands of people working on 18 experiments, seven associated with the LHC and the others with smaller accelerators and a decelerator, which is used for antimatter experiments like those run by Harvard Physics Professor Gerald Gabrielse’s ATRAP collaboration.

    ATRAP, short for “antihydrogen trap,” relies on the LHC’s high energy to make protons collide with a target to create antiprotons. The experiment then cools and slows the antiprotons, and combines them with positrons, the antimatter equivalent of electrons, to create antihydrogen for study and comparison with ordinary hydrogen. Gabrielse, who pioneered antimatter experiments at CERN, said that for students who want to go into high-energy physics, getting a taste of the enormous collaborations that are behind such experiments is key.

    “If you’re interested in making a career in doing those kinds of things [experimental particle physics], it’s extremely important to have this experience,” Gabrielse said.

    The LHC, with its potential to pierce the veil between the known world of the Standard Model and the mysteries that the model does not address, takes center stage. Yet to visitors wandering the halls and sidewalks of CERN, the LHC is nowhere to be seen.

    That’s because the LHC is buried 300 feet underground in a massive tunnel that runs 17 miles from Switzerland into France and back again. Its twin proton beams circle in opposite directions, crossing four times on their journey. At those crossings are four major particle detectors, one of which is ATLAS, a massive machine backed by a worldwide collaboration in which Harvard scientists play lead roles, and which was one of two experiments to detect the Higgs boson.

    CERN/ATLAS detector
    CERN/ATLAS detector

    2
    Outside the ATLAS control room at the LHC. Joe Sherman/Harvard Staff Photographer

    “You can think of it (ATLAS) as a really large camera surrounding the collision point where protons collide,” Tuna said.

    ATLAS, which stands for A Toroidal LHC Apparatus, is 180 feet long, 82 feet in diameter, and weighs 7,000 tons. When the proton beams collide, they scatter particles in all directions. ATLAS dutifully records these collisions, producing far more data than current computing technology can store, so filters are employed that screen out more mundane results and keep only the most promising for analysis.

    The complex undertaking requires a collaboration that is as massive as the task the researchers have set for themselves. It includes about 3,000 physicists from 175 institutions in 38 countries.

    “This is the center of particle physics right now,” said Harvard Ph.D. student Karri DiPetrillo. “As a scientist, you like asking nature questions and seeing what the answer is. Because we have thousands of people working on a single experiment, you know we’re asking some of the hardest questions in the universe. If it takes thousands of people to find the answer, you know that it’s a good question.”

    For decades, physicists exploring the most basic particles that make up the universe were guided by the Standard Model, which held that everything is made of a limited number of quarks, leptons, and bosons. Over the years, one by one, experimental physicists, including Harvard faculty members, found the particles predicted by the theory: bottom quark, W boson, Z boson, top quark. In 2012, they found the Higgs boson, the last theorized particle.

    When the huge hubbub over the Higgs discovery faded, particle physicists began to assess the field’s new reality. After decades in which theoretical physicists were leading, telling experimental physicists what new particle to look for, the roles are now reversed.

    As reliable as the Standard Model has been, it doesn’t explain everything. And, while theoretical physicists have several ideas of where those mysteries might fit into current knowledge, no evidence exists to tip the scales toward one idea or another.

    Even the Higgs boson still holds secrets, as detecting it didn’t completely explain it. Scientists who continue to probe the Higgs boson hope that the particle may yet reveal clues — inconsistencies from what is expected from the Standard Model — that will outline the broader path forward.

    “There are really two paths. One path is to really push on what we understand about the Higgs boson because that has the strangest properties associated with it and if you push the theory at all the Higgs creates the most problems for it,” Huth said. “The other is the discovery region for something new, like dark matter.”

    The undergraduate summer

    A scientist’s path to CERN usually starts with a passion for physics. Graduate student Nathan Jones credits a family road trip to Colorado during which he read a library book about the universe. Undergrad Bledsoe was wowed by a trip to Fermilab outside Chicago as a high school freshman, while grad student Gonski traces it to the annoyance she felt when she learned her high school chemistry teacher had gotten the science wrong.

    “I remember being in chemistry class in high school when they told us protons and neutrons are indivisible,” said Gonski, who learned otherwise from Stephen Hawking’s “A Brief History of Time.” “I was so offended … I remember being frustrated and asking my parents, ‘Did you guys know?’ At that point I wanted to see how far down we can go [in particle size].”

    After that initial spark, students take classes and often work in a campus laboratory before heading overseas. Some undergraduates go to CERN through the Undergraduate Summer Research Experience program run by the University of Michigan for students across the country. Several Harvard students benefitted instead from the Weissman International Internship Program Grant, established in 1994 to provide faraway opportunities for them.


    Access mp4 video here .
    A field of sunflowers stands at the roadside on the approach to CERN.

    Once the funding is set, there’s nothing left but the plane ride and moving into their new digs. Undergraduates live in settings ranging from downtown Geneva to the French countryside. Last summer, three Harvard students — Ben Garber ’17, Gary Putnam ’17, and Bledsoe — rented an apartment over the border in France and commuted to work each day by bike, while Katie Fraser ’18 stayed closer, at CERN’s on-campus hostel.

    Days consisted of morning lectures on topics relevant to their work. After those lectures — and the occasional pickup basketball game at lunchtime — they’d spend afternoons working on a project. Garber worked with Tuna and DiPetrillo on an analysis of Higgs boson decay (the particle itself exists for a tiny period of time) into two W bosons. Bledsoe worked on hardware, building and testing a circuit board to be used in the planned 2018 ATLAS upgrade, in the cavernous Building 188 under the tutelage of Theo Alexopoulos from the Technical University of Athens. Wherever they were, whether doing project tasks or having cafeteria conversations, the students were steeped in physics.

    “It was a lot of fun, different than I expected. You learn stuff just by being there, pick up vocabulary in lunchtime conversations,” Fraser said. “It definitely solidified my desire to go into high-energy physics.”

    Melissa Franklin, Mallinckrodt Professor of Physics, said lessons can be found behind almost every door at CERN.

    “I was just amazed, it was unbelievable,” said Franklin, who first visited between her undergraduate and graduate years. “I went to every place I could on site and just knocked on doors and bugged people … You learn so much by osmosis. You have to learn to hang around and ask good questions.”

    Jennifer Roloff, a Harvard physics Ph.D. student, first came to CERN in 2011 as an undergraduate and has been back every summer. Now she helps manage the University of Michigan summer undergraduate program, which gives her a broad view of the student experience.

    “There are definitely some students who do miss home,” Roloff said. “For a lot of them it’s the first time out of the country [or] the first time long-term out of the country. For a lot of them, they realize this is not what they want to do. CERN is not for everyone. There are challenges and difficulties that are not in other physics.”

    That understanding, Gabrielse said, is as important a lesson as finding your intellectual home.

    “Some decide, based on it, to go into the field. Some decide not to,” Gabrielse said. “That guidance too is valuable.”

    Yet being at CERN is not just about science. Students have their weekends free and can explore their new surroundings. Some hike the Alps or the closer Jura Mountains. Others walk the ancient streets of Geneva, visiting its lakefront, restaurants, museums, and other attractions. Putnam loved a park near the University of Geneva where people played on large chessboards with giant pieces. He also soaked up the area’s natural splendor.

    “It’s so beautiful here,” Putnam said. “Sometimes I forget and do the normal thing of looking down and not paying attention, but being able to look up and see the mountains is really special.”

    On call for a particle emergency

    Life at CERN as graduate students is not quite so fancy-free. Visits are limited to summers early in graduate careers as they complete coursework, but once that’s done, they can come and stay to conduct dissertation research.

    To keep the ATLAS collaboration running, graduate students are required to spend a year of research time doing work to benefit the experiment itself, to ensure that high-quality data is collected, for example, or that potentially significant collision events aren’t lost in the data.

    “We have to make sure the data we’re receiving is like you expect it, ready for analysis,” DiPetrillo said. “[It’s taken] probably half of my time in the last year; the other half has been working on Standard Model measurement of the Z boson.”

    5
    A little physicist humor written on a CERN blackboard. Joe Sherman/Harvard Staff Photographer

    Part of DiPetrillo’s duty is assisting in ATLAS’ day-to-day operation, working in the ATLAS control room — with its Mission Control feel, and dominated by a wall-sized screen — and monitoring one of several subsystems that make the whole operation work. Monitoring those subsystems makes ATLAS a 24/7 proposition.

    In addition to working overnight in the control room, DiPetrillo is often on call to back up someone on site. While on call, she has to stay near her phone and within an hour’s drive of the facility in case something goes wrong. If that happens, she troubleshoots the problem with the person in the control room or pushes the problem up to someone more senior.

    “You can think of ATLAS as always taking data so we always need people watching it, making sure ATLAS is working in a way that we want [it] to, that the detector is working … and that data looks the way we expect,” DiPetrillo said.

    When not on call or manning the control room overnight, a graduate student’s life at CERN is full of meetings to share and hear the latest findings, and of hours poring over the latest data looking for the kind of statistical bump that might indicate a new particle — or a new something else.

    The LHC’s recent upgrade has made scientists hopeful that a new particle will be discovered soon. But if not, another upgrade planned for about 2018 may do the trick. While the recent upgrade made the energy of the proton beam higher, the next one will increase luminosity, or the number of protons in the beam, multiplying the number of collisions at any given moment and improving the odds of detecting extremely rare events.

    “We’re all here to … discover stuff, but it’s so difficult. It’s impossible to do as one person,” Gonski said. “I would love to be one person on the 500-person team to discover [supersymmetry’s] stop quark. It’d be great for physics if we all discovered this and for me to say I want to do this — be a tiny fraction of a large group effort.”

    See the full article here .

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    Harvard University campus

    Harvard is the oldest institution of higher education in the United States, established in 1636 by vote of the Great and General Court of the Massachusetts Bay Colony. It was named after the College’s first benefactor, the young minister John Harvard of Charlestown, who upon his death in 1638 left his library and half his estate to the institution. A statue of John Harvard stands today in front of University Hall in Harvard Yard, and is perhaps the University’s best known landmark.

    Harvard University has 12 degree-granting Schools in addition to the Radcliffe Institute for Advanced Study. The University has grown from nine students with a single master to an enrollment of more than 20,000 degree candidates including undergraduate, graduate, and professional students. There are more than 360,000 living alumni in the U.S. and over 190 other countries.

     
  • richardmitnick 9:01 am on September 23, 2016 Permalink | Reply
    Tags: , , CERN ATLAS,   

    From AARNet: “New record set for elephant data flow over AARNet” 

    aarnet-bloc

    AARNet

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    A new record set for the for the ARC Centre of Excellence in Particle Physics at the University of Melbourne: 53 terabytes transferred in 24hrs sustained at nearly 5 gigabits per second.

    “I think we’ve made a new record for us. 53 terabytes transferred in 24hrs, at 100% efficiency,” reported Sean Crosby to AARNet’s eResearch team. Crosby is a research computing scientist working at the ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP) at the University of Melbourne. He is referring to a recent elephant data flow over the AARNet network between the University of Melbourne and a research network-connected site located in Germany.

    Data processing for the ATLAS Experiment

    This huge data flow forms part of the CoEPP’s activities as an ATLAS experiment Tier2 site for the Worldwide Large Hardron Collider Computing Grid (WLCG). The CoEPP is one of the 170+ grid-connected computing centres in 42 countries worldwide that provide the linked-up computing and storage facilities required for analysing the ~30 Petabytes (30 million gigabytes) of data CERN’s Large Hadron Collider (LHC) produces annually.

    Helping scientists further our understanding of the Universe

    Physicists are using the LHC to recreate the conditions of the Universe just after the ‘Big Bang’. They are searching for new discoveries in the head-on collisions of protons of extraordinarily high energy to further our understanding of energy and matter. Following the discovery of the Higgs boson in 2012, data from the ATLAS experiment allows in-depth investigation of the boson’s properties and the origin of mass.

    The reported 100% efficiency of this particular big data transfer between Australian and Germany, clocked at nearly 5 gigabits per second sustained over 24 hours, is a great example of the reliability and scalability of the AARNet network to meet the needs of data-intensive research on demand.

    See the full article here .

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    AARNet provides critical infrastructure for driving innovation in today’s knowledge-based economy

    Australia’s Academic and Research Network (AARNet) is a national resource – a National Research and Education Network (NREN). AARNet provides unique information communications technology capabilities to enable Australian education and research institutions to collaborate with each other and their international peer communities.

     
  • richardmitnick 8:44 am on September 5, 2016 Permalink | Reply
    Tags: 6 dimensional spacetime, , , CERN ATLAS, , ,   

    From particlebites: “Gravity in the Next Dimension: Micro Black Holes at ATLAS” 

    particlebites bloc

    particlebites

    August 31, 2016
    Savannah Thais

    Article: Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at sqrt(s)=13 TeV
    Authors: The ATLAS Collaboration
    Reference: arXiv:1606.02265 [hep-ex]

    CERN/ATLAS detector
    CERN/ATLAS detector

    What would gravity look like if we lived in a 6-dimensional space-time? Models of TeV-scale gravity theorize that the fundamental scale of gravity, MD, is much lower than what’s measured here in our normal, 4-dimensional space-time. If true, this could explain the large difference between the scale of electroweak interactions (order of 100 GeV) and gravity (order of 1016 GeV), an important open question in particle physics. There are several theoretical models to describe these extra dimensions, and they all predict interesting new signatures in the form of non-perturbative gravitational states. One of the coolest examples of such a state is microscopic black holes. Conveniently, this particular signature could be produced and measured at the LHC!

    Sounds cool, but how do you actually look for microscopic black holes with a proton-proton collider? Because we don’t have a full theory of quantum gravity (yet), ATLAS researchers made predictions for the production cross-sections of these black holes using semi-classical approximations that are valid when the black hole mass is above MD. This production cross-section is also expected to dramatically larger when the energy scale of the interactions (pp collisions) surpasses MD. We can’t directly detect black holes with ATLAS, but many of the decay channels of these black holes include leptons in the final state, which IS something that can be measured at ATLAS! This particular ATLAS search looked for final states with at least 3 high transverse momentum (pt) jets, at least one of which must be a leptonic (electron or muon) jet (the others can be hadronic or leptonic). The sum of the transverse momenta, is used as a discriminating variable since the signal is expected to appear only at high pt.

    This search used the full 3.2 fb-1 of 13 TeV data collected by ATLAS in 2015 to search for this signal above relevant Standard Model backgrounds (Z+jets, W+jets, and ttbar, all of which produce similar jet final states). The results are shown in Figure 1 (electron and muon channels are presented separately). The various backgrounds are shown in various colored histograms, the data in black points, and two microscopic black hole models in green and blue lines. There is a slight excess in the 3 TeV region in the electron channel, which corresponds to a p-value of only 1% when tested against the background only hypothesis. Unfortunately, this isn’t enough evidence to indicate new physics yet, but it’s an exciting result nonetheless! This analysis was also used to improve exclusion limits on individual extra-dimensional gravity models, as shown in Figure 2. All limits were much stronger than those set in Run 1.

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    Figure 1: momentum distributions in the electron (a) and muon (b) channels

    2
    Figure 2: Exclusion limits in the Mth, MD plane for models with various numbers of extra dimensions

    So: no evidence of microscopic black holes or extra-dimensional gravity at the LHC yet, but there is a promising excess and Run 2 has only just begun. Since publication, ATLAS has collected another 10 fb-1 of sqrt(13) TeV data that has yet to be analyzed. These results could also be used to constrain other Beyond the Standard Model searches at the TeV scale that have similar high pt leptonic jet final states, which would give us more information about what can and can’t exist outside of the Standard Model. There is certainly more to be learned from this search!

    See the full article here .

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    What is ParticleBites?

    ParticleBites is an online particle physics journal club written by graduate students and postdocs. Each post presents an interesting paper in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.

    The papers are accessible on the arXiv preprint server. Most of our posts are based on papers from hep-ph (high energy phenomenology) and hep-ex (high energy experiment).

    Why read ParticleBites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.

    Our goal is to solve this problem, one paper at a time. With each brief ParticleBite, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in particle physics.

    Who writes ParticleBites?

    ParticleBites is written and edited by graduate students and postdocs working in high energy physics. Feel free to contact us if you’re interested in applying to write for ParticleBites.

    ParticleBites was founded in 2013 by Flip Tanedo following the Communicating Science (ComSciCon) 2013 workshop.

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    Flip Tanedo UCI Chancellor’s ADVANCE postdoctoral scholar in theoretical physics. As of July 2016, I will be an assistant professor of physics at the University of California, Riverside

    It is now organized and directed by Flip and Julia Gonski, with ongoing guidance from Nathan Sanders.

     
  • richardmitnick 9:11 am on June 30, 2016 Permalink | Reply
    Tags: , CERN ATLAS, , Muhammad Alhroob   

    From ATLAS at CERN: “A busy day in the life of high energy physicist” Muhammad Alhroob 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLASATLAS

    27th June 2016
    Muhammad Alhroob

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    Muhammad on shift in the ATLAS Control Room. (Image: ATLAS Experiment/CERN)

    Let me start off with a short introduction: my name is Muhammad Alhroob, and I am an international person working at an international organization. I was born and raised in Palestine, which is where I obtained my Bachelor’s degree in Physics. I then travelled to Trieste, Italy to obtain a diploma in theoretical high-energy physics from the Abdus Salam International Center for Theoretical Physics (ICTP). It was named after Abdus Salam, one of the theorists responsible for developing the Standard Model theory of particle physics.

    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    I carried out my Doctoral studies at Bonn University, Germany, in experimental particle physics with the ATLAS experiment. Currently, I work as a post-doctoral researcher as a member of the ATLAS experiment and I am employed by the University of Oklahoma, USA. I live in France, but my office and work is in Switzerland!

    My work involves analyzing data to try to understand how nature works at the most fundamental level, by searching for new particles and ways in which they interact. Specifically, I am looking at the top quark, which is the heaviest fundamental particle known to exist, with a mass of about 180 times that of a proton.

    The top quark was discovered in 1995 at Fermilab near Chicago, USA.

    2

    It is predicted by the Standard Model to be produced in two ways: in pairs (a top quark and its antimatter partner) via the strong interaction or singly via the weak interaction. The top quark decays spontaneously to a bottom quark and a W boson, exclusively via the weak interaction. Its heavy mass and very fast decay make it a fantastic for probing the Standard Model.

    I am looking for the top quark when it is produced together with a Z boson. This allows us to measure the strength of the coupling between the top quark and the Z boson, which is a parameter in the Standard Model that has to be determined. This channel allows us to probe for physics beyond the Standard Model.

    This process is also the main background of another extremely important signal: the production of the top quark in association with the Higgs boson (tH). This background has to be measured very precisely and understood. The tH signal will allow us to measure the strength of the coupling between the top quark and the Higgs boson, which is also a free parameter in the Standard Model that needs to be measured. This channel uniquely allows for the structure and nature of the coupling to be studied.

    My work day starts around 9 a.m. as I arrive at CERN and grab a cup of coffee, sometimes with colleagues. Once I am at the office, I read and reply to dozens of emails, edit and debug computer programs, and submit jobs to the Grid. Sometimes my morning involves a chat via Skype or a meeting via video conference. Lunch starts at 12 and can involve physics and detector operation discussion. Therefore, it can sometimes last for as long as 2 hours. My afternoon is usually busy with all kinds of meetings: physics meetings, detector and performance meetings, and ATLAS general meetings. By then it is 5 or 6 p.m. and people have started to leave, giving me the opportunity to stay in the office to concentrate on the job and incorporate the things I learned during the day.

    Afterwards, I need to go home and sleep one or two hours before my night shift in the ATLAS control room starts. I am currently doing shifts to monitor the inner detector of the experiment. It starts at 11 p.m. and ends the next day at 7 a.m. I have as many as two to three night shifts per month. These shifts are extremely important to keep the detector running in good condition and to guarantee the high quality of the collected data.

    When I don’t have a shift, I get a full night’s sleep, hoping for another good day, full of excitement and interesting activities!

    See the full article here .

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    LHC at CERN

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  • richardmitnick 6:49 am on May 10, 2016 Permalink | Reply
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    From Cern Atlas: “ATLAS continues to explore the 13 TeV frontier” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    9th May 2016

    ATLAS is back and better than ever! With 13 TeV beams circulating in the Large Hadron Collider, the ATLAS experiment is now recording data for physics. This milestone marks the start of the second year of “Run 2” as ATLAS continues its exploration of 13 TeV energy frontier.

    Anticipation is high for 2016, with the year set to deliver exciting new results for physicists around the world. From precision studies of the Higgs boson to searches for new particles, this year’s data will deepen our understanding of Nature. “We welcome the first 13 TeV collisions of the year with the careful preparation and great expectations of a good friend’s anticipated encounter,” says Alessandro Cerri, ATLAS Run Co-Coordinator. “Together, we are ready for new, exciting explorations!”

    1
    One of the early collision events with stable beams recorded by ATLAS in 2016. (Image: ATLAS Experiment/CERN)

    Today’s smooth start was thanks to the hard work and dedication of countless ATLAS teams. ATLAS physicists were able to hit the ground running, harnessing last year’s experience running at 13 TeV. “The ATLAS teams have done an incredible job to further improve the performance of the detector and get the systems up and running again in step with the swift start-up of LHC in 2016,” says Alex Oh, ATLAS Run Co-Coordinator. “It’s going to be an exiting year for ATLAS and the other LHC experiments with hopefully great discoveries to be made.”

    “The mission of the data preparation team is to get the best quality data to the physics analysis teams as quickly as possible. We’ve learned from our experience in 2015 and this year we will be faster, with even better data quality,” adds Paul Laycock, ATLAS Data Preparation Coordinator.

    Over the next 6 months of operation with proton beams, the ATLAS experiment will see up to a billion collisions per second. Selecting the most interesting of these collisions is the ATLAS trigger: “It is with great excitement and satisfaction we see the ATLAS trigger system smoothly selecting events for analysis; the many months of preparation and the long nights our experts spent at the control room certainly paid off!” says Anna Sfyrla, ATLAS Trigger Coordinator. “We now need to be patient for more LHC data to come and look into them for the next surprises Nature holds for us.”

    “2015 was like watching the film trailer, there were tantalising glimpses of something amazing happening,” concludes Paul Laycock. “In 2016 we’re looking forward to watching the whole film!”

    See the full article here .

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  • richardmitnick 9:52 am on March 25, 2016 Permalink | Reply
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    From LHC/ATLAS at CERN: “Spring awakening for the ATLAS experiment” 

    CERN ATLAS Higgs Event

    CERN/ATLAS
    ATLAS

    24th March 2016
    Katarina Anthony

    This morning the Large Hadron Collider (LHC) circulated the first proton-proton beams of 2016 around its 27 kilometre circumference. The beams were met with great enthusiasm in the ATLAS Control Centre as they passed through the ATLAS experiment.

    These beams mark the start of an exciting new period for ATLAS and other CERN experiments. Having seen tantalising but still inconclusive signals in 2015, ATLAS physicists around the world are eagerly awaiting new data to analyse.

    The start of a new run also means the conclusion of a maintenance period, known as the Year-End-Technical-Stop (YETS). This 3 month-long upkeep is vital for the health and well-being of the detectors, ensuring that ATLAS can function impeccably for the 9 straight months of operation that follow.

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    ATLAS uses “beam splash” events to provide simultaneous signals to large parts of the detector, and verify that the readout of different detectors elements are fully synchronized. (Image: ATLAS Experiment © 2016 CERN)

    “This is a normal period of maintenance that happens yearly,” says Michel Raymond, ATLAS Deputy Technical Coordinator. “At ATLAS we use this time to repair and consolidate the detectors first, but also all the infrastructure around that allows us to run the detector.”

    But before their work can begin, there is a lot preparation needed. Although located in an enormous 52,500 m3 cavern, the ATLAS experiment fills that space nearly to the brink. Whatever room is left over is devoted to the cabling and cooling infrastructure that keeps the experiment running. “You cannot just go in and start working on a detector element,” says Raymond. “We first need to move the shielding and cabling to get the experiment into a configuration where the requested detector is accessible.”

    Moving these elements is called “opening” the detector and can take at least 3 weeks. The ATLAS teams have to go slowly and carefully, as they are moving fragile equipment that can weigh anywhere between 100 to 1000 tonnes.

    Once the detector elements are accessible, the teams have only a few weeks to get to work before they need to start closing the detector back up. “Every hour in the cavern is precious,” says Raymond. “We prioritise in advance what operations are the most important, and which can wait for next maintenance period.

    2
    This display shows one of the ATLAS Experiment’s first splashes on 2016, with beam 1 at 10:26 a.m. on Friday 25th March 2016. (Image: ATLAS Experiment © 2016 CERN)

    During this YETS period, the main priority was the repair of ATLAS’ end-cap magnet bellows. These bellows protect the integrity of the vacuum surrounding ATLAS cooling elements, and are essential for keeping the magnet system cool. They were damaged during a previous maintenance period though continued to work adequately throughout 2015. The damage was successfully repaired during this recent shutdown.

    “After that, we took action on the detector elements, repairing wear-and-tear damage,” says Raymond. “There was a lot of work needed on the muon chambers and the Tile Calorimeters, replacing faulty electronic elements; and a number of gas connections had to be replaced on both sides of the experiment, to avoid leaks.”

    With the work now complete and beams running through the LHC, most of the ATLAS Collaboration has turned their focus to the data. However Michel and his colleagues continue to look forward to their next trip underground. “We’re always planning ahead, thinking about the next shutdown and the ones after that,” concludes Raymond.

    See the full article here .

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  • richardmitnick 9:03 pm on December 28, 2015 Permalink | Reply
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    From DESY: “ERC Starting Grant for characterising the Higgs boson” 

    DESY
    DESY

    2015/12/28
    No writer credit found

    Temp 1
    No image credit found

    Kerstin Tackmann, a physicist at DESY, is to receive over 1.3 million euros from the European Research Council (ERC) in order to carry out research aimed at a more detailed characterisation of the Higgs boson.

    CERN ATLAS Higgs Event
    Higgs event at ATLAS

    She will use a starting grant to set up a research group to investigate the properties of the Higgs boson in great detail, as part of the international ATLAS Collaboration.

    CERN ATLAS New
    ATLAS

    These measurements are an important step towards identifying whether the particle fits the Standard Model of particle physics. The 5-year project is scheduled to begin in 2016.

    Ever since particle physicists working on the big LHC experiments ATLAS and CMS announced, in 2012, the discovery of a particle whose properties corresponded to those of the elusive Higgs boson, particle physics has faced an extremely exciting mystery: does this Higgs boson fit the Standard Model of particle physics, the currently accepted description of the elementary particles that make up matter and the forces acting between them, or will it open the path to a new, higher-level theory.

    CERN LHC Map
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    CERN LHC particles
    LHC at CERN

    CERN CMS Detector
    CMS

    CERN CMS Event
    CMS Higgs event

    Standard model with Higgs New
    Standard Model of Particle Physics

    Using the data available so far, scientists have already been able to determine the particle’s mass of around 125 gigaelectronvolts (GeV) and its spin of zero to a fairly high degree of accuracy. To obtain even more precise information about additional properties of the particle, the researchers need to analyse far more data from proton-proton collisions in the LHC. They are particularly interested in finding out exactly how the Higgs field, of which the Higgs boson is an indication, lends elementary particles their mass. To answer this question, they have started to analyse the collision data from “LHC Run 2”, which began this summer and which is expected to produce about 15 times as many Higgs bosons as the LHC’s previous run. The analysis of this large amount of collision data will allow far more reliable conclusions to be drawn.

    Kerstin Tackmann intends to devote herself to these questions together with two post-docs and three PhD students, and will be analysing the collisions from Run 2 of the ATLAS detector in great detail. They will be working as part of the ATLAS Collaboration, involving hundreds of scientists from all over the world. Her group is going to concentrate on measuring the kinematic properties of Higgs boson production. The focus will lie especially on the decay of the Higgs boson into two photons or four leptons, which allows very accurate measurements to be made. This is where deviations from the precise predictions of the Standard Model could occur, should the Higgs boson not fit the Standard Model.

    See the full article here .

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    desi

    DESY is one of the world’s leading accelerator centres. Researchers use the large-scale facilities at DESY to explore the microcosm in all its variety – from the interactions of tiny elementary particles and the behaviour of new types of nanomaterials to biomolecular processes that are essential to life. The accelerators and detectors that DESY develops and builds are unique research tools. The facilities generate the world’s most intense X-ray light, accelerate particles to record energies and open completely new windows onto the universe. 
That makes DESY not only a magnet for more than 3000 guest researchers from over 40 countries every year, but also a coveted partner for national and international cooperations. Committed young researchers find an exciting interdisciplinary setting at DESY. The research centre offers specialized training for a large number of professions. DESY cooperates with industry and business to promote new technologies that will benefit society and encourage innovations. This also benefits the metropolitan regions of the two DESY locations, Hamburg and Zeuthen near Berlin.

     
  • richardmitnick 8:29 pm on December 16, 2015 Permalink | Reply
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    From CERN: “ATLAS and CMS present their 2015 LHC results” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    16 Dec 2015
    Corinne Pralavorio

    1
    A 13 TeV collision recorded by ATLAS. The yellow and green bars indicate the presence of particle jets, which leave behind lots of energy in the calorimeters. (Image: ATLAS)

    2
    A 13 TeV proton collision recorded by CMS. The two green lines show two photons generated by the collision. (Image: CMS)

    Particles circulated in the Large Hadron Collider (LHC) on Sunday for the last time in 2015, and, two days later, the two large general-purpose experiments, ATLAS and CMS, took centre stage to present their results from LHC Run 2. These results were based on the analysis of proton collisions at the previously unattained energy of 13 TeV, compared with the maximum of 8 TeV attained during LHC Run 1 from 2010 to 2012.

    The amount of data on which the two experiments’ analyses are based is still limited – around eight times less than that collected during Run 1 – and physicists need large volumes of data to be able to detect new phenomena. Nonetheless, the experimentalists have already succeeded in producing numerous results. Each of the two experiments has presented around 30 analyses, about half of which relate to Beyond-Standard-Model research. The Standard Model is the theory that describes elementary particles and their interactions, but it leaves many questions unanswered. Physicists are therefore searching for signs of Beyond-Standard-Model physics that might help them to answer some of those questions.

    The new ATLAS and CMS results do not show any significant excesses that could indicate the presence of particles predicted by alternative models such as supersymmetry. The two experiments have therefore established new limits for the masses of these hypothetical new particles. Advances in particle physics often come from pushing back these limits. For example, CMS and ATLAS have established new restrictions for the mass of the gluino, a particle predicted by the theory of supersymmetry. This is just one of the many results that were presented on 15 December.

    The two experiments have also observed a slight excess in the diphoton decay channel. Physicists calculate the mass of hypothetical particles that decay to form a pair of photons, and look at how often different masses are seen. If the distribution does not exactly match that expected from known processes, or in other words a bump appears at a specific mass not corresponding to any known particle, it may indicate a new particle being produced and decaying. However, the excess is too small at this stage to draw such a conclusion. We will have to wait for more data in 2016 to find out whether this slight excess is an inconsequential statistical fluctuation or, alternatively, a sign of the existence of a new phenomenon. Find out next time: season 2 is only just beginning.

    The presentations by ATLAS and CMS are available here.

    See the full article here.

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    Meet CERN in a variety of places:

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    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
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    CERN ALICE New

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    CERN CMS New

    LHCb
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    Quantum Diaries

     
  • richardmitnick 8:11 pm on December 16, 2015 Permalink | Reply
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    From Pauline Gagnon at Quantum Diaries: “If, and really only if…” 

    12.16.15

    Pauline Gagnon
    Pauline Gagnon

    On December 15, at the End-of-the-Year seminar, the CMS and ATLAS experiments from CERN presented their first results using the brand new data accumulated in 2015 since the restart of the Large Hadron Collider (LHC) at 13 TeV, the highest operating energy so far.

    CERN CMS Detector
    CMS

    CERN ATLAS New
    ATLAS

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    Although the data sample is still only one tenth of what was available at lower energy (namely 4 fb-1 for ATLAS and 2.8-1 fb for CMS collected at 13 TeV compared to 25 fb-1 at 8 TeV for each experiment), it has put hypothetical massive particles within reach. If the LHC were a ladder and particles, boxes hidden on shelves, operating the LHC at higher energy is like having a longer ladder giving us access to higher shelves, a place never checked before. ATLAS and CMS just had their first glimpse at it.

    Both experiments showed how well their detectors performed after several major improvements, including collecting data at twice the rate used in 2012. The two groups made several checks on how known particles behave at higher energy, finding no anomalies. But it is in searches for new, heavier particles that every one hopes to see something exciting. Both groups explored dozens of different possibilities, sifting through billions of events.

    Each event is a snapshot of what happens when two protons collide in the LHC. The energy released by the collision materializes into some heavy and unstable particle that breaks apart mere instants later, giving rise to a mini firework. By catching, identifying and regrouping all particles that fly apart from the collision point, one can reconstruct the original particles that were produced.

    Both CMS and ATLAS found small excesses when selecting events containing two photons. In several events, the two photons seem to come from the decay of a particle having a mass around 750 GeV, that is, 750 times heavier than a proton or 6 times the mass of a Higgs boson.

    CERN ATLAS Higgs Event
    Higgs event at ATLAS

    Since the two experiments looked at dozens of different combinations, checking dozens of mass values for each combination, such small statistical fluctuations are always expected.

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    Top part: the combined mass given in units of GeV for all pairs of photons found in the 13 TeV data by ATLAS. The red curve shows what is expected from random sources (i.e. the background). The black dots correspond to data and the lines, the experimental errors. The small bump at 750 GeV is what is now intriguing. The bottom plot shows the difference between black dots (data) and red curve (background), clearly showing a small excess of 3.6σ or 3.6 times the experimental error. When one takes into account all possible fluctuations at all mass values, the significance is only 2.0σ

    What’s intriguing here is that both groups found the same thing at exactly the same place, without having consulted each other and using selection techniques designed not to bias the data. Nevertheless, both experimental groups are extremely cautious, stating that a statistical fluctuation is always possible until more data is available to check this with increased accuracy.

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    CMS has slightly less data than ATLAS at 13 TeV and hence, sees a much smaller effect. In their 13 TeV data alone, the excess at 760 GeV is about 2.6σ, 3σ when combined with the 8 TeV data. But instead of just evaluating this probability alone, experimentalists prefer take into account the fluctuations in all mass bins considered. Then the significance is only 1.2σ, nothing to write home about. This “look-elsewhere effect” takes into account that one is bound to see a fluctuation somewhere when ones look in so many places.

    Theorists show less restrain. For decades, they have known that the Standard Model, the current theoretical model of particle physics, is flawed and have been looking for a clue from experimental data to go further.

    4
    The Standard Model of elementary particles (more schematic depiction), with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    Many of them have been hard at work all night and eight new papers appeared this morning, proposing different explanations on which new particle could be there, if something ever proves to be there. Some think it could be a particle related to Dark Matter, others think it could be another type of Higgs boson predicted by Supersymmetry or even signs of extra dimensions. Others offer that it could only come from a second and heavier particle. All suggest something beyond the Standard Model.

    Two things are sure: the number of theoretical papers in the coming weeks will explode. But establishing the discovery of a new particle will require more data. With some luck, we could know more by next Summer after the LHC delivers more data. Until then, it remains pure speculation.

    This being said, let’s not forget that the Higgs boson made its entry in a similar fashion. The first signs of its existence appeared in July 2011. With more data, they became clearer in December 2011 at a similar End-of-the-Year seminar. But it was only once enough data had been collected and analysed in July 2012 that its discovery made no doubt. Opening one’s gifts before Christmas is never a good idea.

    See the full article here .

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    Participants in Quantum Diaries:

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