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  • richardmitnick 3:06 pm on July 12, 2016 Permalink | Reply
    Tags: A primer on particle accelerators, Accelerator Science, ,   

    From Symmetry: “A primer on particle accelerators” 

    Symmetry Mag

    Symmetry

    07/12/16
    Signe Brewster

    1
    Illustration by Sandbox Studio, Chicago with Jill Preston

    Research in high-energy physics takes many forms. But most experiments in the field rely on accelerators that create and speed up particles on demand.

    What follows is a primer on three different types of particle accelerators: synchrotrons, cyclotrons and linear accelerators, called linacs.

    Synchrotrons: the heavy lifters
    2

    Synchrotrons are the highest-energy particle accelerators in the world. The Large Hadron Collider currently tops the list, with the ability to accelerate particles to an energy of 6.5 trillion electronvolts before colliding them with particles of an equal energy traveling in the opposite direction.

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

    Synchrotrons typically feature a closed pathway that takes particles around a ring. Other variants are created with straight sections between the curves (similar to a racetrack or in the shape of a triangle or hexagon). Once particles enter the accelerator, they travel around the circular pathway over and over again, always enclosed in a vacuum pipe.

    Radiofrequency cavities at intervals around the ring increase their speed. Several different types of magnets create electromagnetic fields, which can be used to bend and focus the particle beams. The electromagnetic fields slowly build up as the particles are accelerated. Particles pass around the LHC about 14 million times in the 20 minutes they need to reach their intended energy level.

    Researchers send beams of accelerated particles through one another to create collisions in locations surrounded by particle detectors. Relatively few collisions happen each time the beams meet. But because the particles are constantly circulating in a synchrotron, researchers can pass them through one another many times over—creating a large number of collisions over time and more data for observing rare phenomena.

    “The LHC detectors ATLAS and CMS reached about 400 million collisions a second last year,” says Mike Lamont, head of LHC operations at CERN. “This is why this design is so useful.”

    CERN/ATLAS detector
    CERN ATLAS Higgs Event
    CERN/ATLAS detector; CERN ATLAS Higgs Event

    CERN/CMS Detector
    CERN CMS Higgs Event
    CERN/CMS detector; CERN CMS Higgs Event

    Synchrotrons’ power makes them especially suited to studying the building blocks of our universe. For example, physicists were able to witness evidence of the Higgs boson among the LHC’s collisions only because the collider could accelerate particles to such a high energy and produce such high collision rates.

    The LHC primarily collides protons with protons but can also accelerate heavy nuclei such as lead. Other synchrotrons can also be customized to accelerate different types of particles. At Brookhaven National Laboratory [BNL] in New York, the Relativistic Heavy Ion Collider [RHIC] can accelerate everything from protons to uranium nuclei.

    BNL RHIC Campus
    BNL/RHIC

    It keeps the proton beams polarized with the use of specially designed magnets, according to RHIC accelerator physicist Angelika Drees. It can also collide heavy ions such as uranium and gold to create quark-gluon plasma—the high-temperature soup that made up the universe just after the Big Bang.

    Cyclotrons: the workhorses
    3
    Synchrotrons are the descendants of another type of circular collider called cyclotrons. Cyclotrons accelerate particles in a spiral pattern, starting at their center.

    Like synchrotrons, cyclotrons use a large electromagnet to bend the particles in a circle. However, they use only one magnet, which limits how large they can be. They use metal electrodes to push particles to travel in increasingly large circles, creating a spiral pathway.

    Cyclotrons are often used to create large amounts of specific types of particles, such as muons or neutrons. They are also popular for medical research because they have the right energy range and intensity to produce medical isotopes.

    The world’s largest cyclotron is located at the TRIUMF laboratory in Vancouver, Canada.

    4
    INSIDE the TRIUMF 520 MeV CYCLOTRON Inside the Cyclotron with the lid raised for servicing

    At the TRIUMF cyclotron, physicists regularly accelerate particles to 520 million electronvolts. They can draw particles from different parts of their accelerator for experiments that require particles at different energies. This makes it an especially adaptable type of accelerator, says physicist Ewart Blackmore, who helped to design and build the TRIUMF accelerator.

    “We certainly make use of that facility every day when we’re running, when we’re typically producing a low-energy but high-current beam for medical isotope production,” Blackmore says. “We’re extracting at fixed energies down one beam for producing pions and muons for research, and on another beam line we’re extracting beams of radioactive nuclei to study their properties.”

    Linacs: straight and to the point
    6
    For physics experiments or applications that require a steady, intense beam of particles, linear accelerators are a favored design. SLAC National Accelerator Laboratory hosts the longest linac in the world, which measures 2 miles long and at one point could accelerate particles up to 50 billion electronvolts.

    SLAC Campus
    LINAC st SLAC

    Fermi National Accelerator Laboratory uses a shorter linac to speed up protons before sending them into a different accelerator, eventually running the particles into a fixed target to create the world’s most intense neutrino beam.

    While circular accelerators may require many turns to accelerate particles to the desired energy, linacs get particles up to speed in short order. Particles start at one end at a low energy, and electromagnetic fields in the linac accelerate them down its length. When particles travel in a curved path, they release energy in the form of radiation. Traveling in a straight line means keeping their energy for themselves. A series of radiofrequency cavities in SLAC’s linac are used to push particles on the crest of electromagnetic waves, causing them to accelerate forward down the length of the accelerator.

    Like cyclotrons, linacs can be used to produce medical isotopes. They can also be used to create beams of radiation for cancer treatment. Electron linacs for cancer therapy are the most common type of particle accelerator.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 10:48 am on July 9, 2016 Permalink | Reply
    Tags: Accelerator Science, , ,   

    From Ethan Siegel: “Did The LHC Discover A New Type Of Particle?” 

    From Ethan Siegel

    Jul 9, 2016

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

    1
    The CMS detector at CERN, one of the two most powerful particle detectors ever assembled. Image credit: CERN.

    In the quest to advance our knowledge of the Universe, the biggest advances always seem to come when an experiment or measurement indicates something new: something our best theories to that date hadn’t predicted before. We all know that the LHC is looking for fundamental particles beyond the Standard Model, including hints of supersymmetry, technicolor, extra dimensions and more. Is it possible that the LHC just discovered a new type of particle, and the results just got buried in the news? That’s the question of Andrea Lelli, who wants to know why

    ” the news about tetraquark particles discovered in the LHC was published in some scientific feeds, but it seems the news did not catch mainstream attention. Isn’t this a valuable discovery, even though tetraquarks were already theorized? What does it mean for the standard model exactly?”

    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.

    Let’s find out.

    2
    The particles and antiparticles of the Standard Model. Image credit: E. Siegel.

    When it comes to the particles we know in the Universe, we have:

    the quarks, which make up protons and neutrons (among other things)
    the leptons, including the electron and the very light neutrinos,
    the antiquarks and antileptons, the antiparticle counterparts of the above two classes,

    we have the photon, the particle version of what we call light,
    we have the gluons, which bind the quarks together and are responsible for the strong nuclear force,
    we have the heavy gauge bosons — the W+, W- and the Z0 — which mediate the weak interactions and radioactive decays,
    and the Higgs boson.

    The main goal of the LHC was to find the Higgs, which it did, completing the gamut of expected particles in the Standard Model.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    The stretch goal, however, was to find new particles beyond the ones we expected. We hopes to find clues to the greatest unsolved problems in theoretical physics at these high energies. To find something that could provide a hint to dark matter, the matter-antimatter asymmetry of the Universe, the reason particles have the masses they do, the reason strong decays don’t occur in certain fashions, etc. To find a new fundamental particle, and to give us either experimental support for a speculative theoretical idea or to surprise us, and push us in a new direction entirely.

    The closest we’ve gotten to that is a “hint” of a new particle whose decay shows up in the two-photon channel at 750 GeV. The threshold for discovery, however, requires a significance indicating there’s less than a 0.00003% chance of a fluke; the CMS and ATLAS data are at a 3% and a 10% chance of a fluke, respectively. That’s a pretty tenuous hint.

    4
    The ATLAS and CMS diphoton bumps, displayed together, clearly correlating at ~750 GeV. Image credit: CERN, CMS/ATLAS collaborations, image generated by Matt Strassler at https://profmattstrassler.com/2015/12/16/is-this-the-beginning-of-the-end-of-the-standard-model/.

    But the LHC does have a few new discoveries under its belt, although they aren’t quite fundamental discoveries in the “new particle” sense. What we got instead, however, was an announcement about the discovery of tetraquarks.

    5
    New Tetraquark Particle Found At Fermilab

    These aren’t new particles that are additions or extensions to the standard model: they don’t represent new forces, new interactions, or potential solutions to any of the great, outstanding problems of theoretical physics today. Rather, they’re entirely combinations of the existing particles that have never been seen before.

    The way quarks work is they come with a color: red, green or blue. (Antiquarks are cyan, magenta and yellow, respectively: the anti-colors of the quarks.) Gluons are exchanged between quarks to mediate the strong nuclear force, and they change the quark (or antiquark) colors when they do. But here’s the kicker: in order to exist in nature, any combination of quarks or antiquarks must be completely colorless. So you can have:

    Three quarks, since red+green+blue = colorless.
    Three antiquarks, since cyan+magenta+yellow = colorless.
    Or a quark-antiquark combination, since red+cyan (i.e., anti-red) = colorless.

    5
    Image credit: Wikipedia / Wikimedia Commons user Qashqaiilove.

    (You can also think of colors as “arrow” vectors in particular directions, and you have to get back to the origin to make something colorless.)

    The three quark combinations are known as baryons, and protons and neutrons are two such examples, along with more exotic combinations involving heavier quarks. Combinations of three antiquarks are known as anti-baryons, and include anti-protons and anti-neutrons. And the quark-antiquark combinations are known as mesons, which mediate the forces between atomic nuclei and have interesting life-and-decay properties on their own. Meson examples include the pion, the kaon, charmonium and the upsilon.

    But why stop there? Why not envision other color-free combinations? Why not something like:

    Two quarks and two antiquarks, a tetraquark?
    Or four quarks and one antiquark, a pentaquark?
    Or even something like five quarks and two antiquarks, a septaquark?

    6
    A pentaquark mass state discovered at the LHCb collaboration in 2015. The “spike” corresponds to the pentaquark. Image credit: CERN on behalf of the LHCb collaboration.

    (Having six quarks isn’t interesting or new: we already know how to make deuterium, a heavy isotope of hydrogen.) According to the Standard Model, this is not only possible, this is predicted. It’s a natural consequence of quantum chromodynamics: the science behind the strong nuclear force and those interactions.

    In the early 2000s, it was claimed that pentaquarks — these five quark/antiquark combinations — were discovered. Unfortunately, this was premature, as the 2003 result from Japan’s Laser Electron Photon Experiment at SPring-8 (LEPS) was unable to be reproduced and the other mid-2000s results were of poor significance. Tetraquark states were coming out at right around the same time. In 2003, the Belle experiment (also in Japan) announced a very controversial result: the discovery of a particle with a mass of 3872 MeV/c2 whose quantum numbers did not match any feasible baryon or meson-like states. For the first time, we had a tetraquark candidate.

    KEK Belle detector
    KEK Belle detector

    7
    Colour flux tubes produced by a configuration of four static quark-and-antiquark charges, representing calculations done in lattice QCD. Image credit: Wikimedia Commons user Pedro.bicudo, under a c.c.a.-s.a.-4.0 license.

    Belle went on, in 2007, to discover two other tetraquark candidates, including the first one with charm quarks inside of it, while Fermilab also uncovered a number of tetraquark candidates. But the biggest breakthrough in these “other” combination states came in 2013, when both Belle and the BES III experiment (in China) independently reported the discovery of the first confirmed tetraquark state.

    8
    BESIII detector

    It was the first tetraquark to be directly observed experimentally. Just like pions, it comes in positively charged, negatively charged and also neutral versions.

    Since then, the LHC has taken the lead, collecting more data on high-energy hadrons than any other experiment before it. The LHCb experiment, in particular, is the one designed to observe these particles. Some tetraquark candidates — like Fermilab’s bottom-quark containing candidate from the DØ experiment — were disfavored by the LHC. But others were directly observed, like Belle’s 2007 charm-containing tetraquark along with many new ones. And the latest tetraquark results that you allude to, reported here in Symmetry Magazine, detail four new tetraquark particles.

    7
    The LHCb detector room at CERN. Image credit: CERN.

    Symmetry Mag
    Symmetry, a journal of FNAL and SLAC, both USA

    The cool thing about these four new particles is that they’re made up of two charm and two strange quarks apiece (with two always being the “anti” version), making these the first tetraquarks to have no light (up and down) quarks in them. And just like you can have a single electron within an atom exist in many different unique states, the way these quarks are configured means that each of these particles have unique quantum numbers, including mass, spin, parity, and charge conjugation. Physicist Thomas Britton, who did much of this work for his Ph.D., detailed:

    We looked at every known particle and process to make sure these four structures couldn’t be explained by any pre-existing physics. It was like baking a six-dimensional cake with 98 ingredients and no recipe—just a picture of a cake.

    In other words, we’re 100% positive these aren’t any normal hadrons the Standard Model could have predicted, and pretty sure these really are tetraquarks!

    8
    B mesons can decay directly into a J/Ψ (psi) particle and a Φ (phi) particle. The CDF scientists found evidence that some B mesons unexpectedly decay into an intermediate quark structure identified as a Y particle. Image credit: Symmetry Magazine.

    The way they normally show up — as the picture details above — is by showing up in an intermediate stage (indicated by Y) of some decays. This is completely allowed by the Standard Model, but it’s a very rare process and so, in some sense, it’s amazing that we have the sheer amount of data and can measure it precisely enough to detect these classes of particles at all. Tetraquarks, pentaquarks and even higher combinations are expected to be real. Perhaps most oddly of all, the Standard Model predicts the existence of glueballs, which are bound states of gluons.

    It’s important to remember that in doing these tests, and in looking for these incredibly rare and difficult-to-find states of nature, we are doing the highest-precision tests of QCD — the theory underlying the strong force — of all-time. If these predicted states of quarks, antiquarks and gluons fail to materialize, then something about QCD is wrong, and that would be a way of going beyond the Standard Model, too! Finding these states is the first step; understanding the details of how they fit together, what their hierarchies are and how our known physics applies to these more and more complex systems is what comes next. As with everything in nature, the payoff for human advancement is hard to see when the initial discovery is made, but the joy of finding things out is always its own reward.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 12:51 pm on July 7, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , , Testing calorimeters at CERN   

    From ILC: “Practi-Cal” 

    Linear Collider Collaboration header
    Linear Collider Collaboration

    7 July 2016
    No writer credit found

    1
    Testing, testing… calorimeters in the test beam at CERN.

    Better together: two technological prototypes of the high-granularity calorimeters for a future ILC detector have been tested together with particle beams at CERN in a combined mode. The Semi-Digital Hadronic CALorimeter (SDHCAL) prototype with its 48 layers and the Silicon Electromagnetic CALorimeter (SiECAL) with its 10 units, both part of the CALICE collaboration, spent two weeks taking data on the “H2” beam line at CERN’s SPS. The principal goal of this beam test was to validate their combined data acquisition (DAQ) system developed by the teams working on the two calorimeters. After the fixing of a few problems that appeared during the data taking, the DAQ system ran smoothly and both prototypes took common data. This is what they will have to do in the future to register electron-positron collisions at the ILC.

    Physicists and engineers from six countries participated in this beam test: Belgium, China, France, Japan, Korea and Spain. Future tests will focus on studying the common response of these two calorimeters to the different kinds of particles. “The success of this combined test will certainly encourage other detectors proposed for the tracking system (Silicon and TPC detectors) to join the adventure…,” Imad Laktineh, professor at IN2P3’s Institut de Physique Nucléaire de Lyon,who supervised the combined beam test, hopes.

    More about calorimeter test beams here and here.

    See the full article here .

    Please help promote STEM in your local schools.

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    The Linear Collider Collaboration is an organisation that brings the two most likely candidates, the Compact Linear Collider Study (CLIC) and the International Liner Collider (ILC), together under one roof. Headed by former LHC Project Manager Lyn Evans, it strives to coordinate the research and development work that is being done for accelerators and detectors around the world and to take the project linear collider to the next step: a decision that it will be built, and where.

    Some 2000 scientists – particle physicists, accelerator physicists, engineers – are involved in the ILC or in CLIC, and often in both projects. They work on state-of-the-art detector technologies, new acceleration techniques, the civil engineering aspect of building a straight tunnel of at least 30 kilometres in length, a reliable cost estimate and many more aspects that projects of this scale require. The Linear Collider Collaboration ensures that synergies between the two friendly competitors are used to the maximum.

    Linear Collider Colaboration Banner

     
  • richardmitnick 2:23 pm on June 17, 2016 Permalink | Reply
    Tags: Accelerator Science, , CERN Super Proton Synchrotron,   

    From CERN: “Happy Birthday SPS!” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    17 Jun 2016
    Corinne Pralavorio

    CERN Super Proton Synchrotron
    40 years ago this week, the Super Proton Synchrotron accelerated its first particles (Image: Piotr Traczyk/CERN)

    The Super Proton Synchrotron (SPS), CERN’s second-largest accelerator, is celebrating its 40th birthday. But the 7-kilometre-circumference accelerator is not getting a break for the occasion: it will continue to supply the Large Hadron Collider (LHC) and several fixed-target experiments with protons and heavy ions.

    The SPS began life in a particularly spectacular fashion. On 17 June 1976, the machine, a giant among its contemporaries, accelerated protons to 300 gigaelectronvolts (GeV) for the first time. During his announcement of the successful start-up to the CERN Council, the Director-General, John Adams, who had led the design of the SPS, requested authorisation to increase the brand-new accelerator’s energy. Just a few minutes later, it reached an energy of 400 GeV.

    A second key moment for the accelerator came five years later, when, in a real technological masterstroke, it was transformed into a proton-antiproton collider. This revolutionary collider allowed the discovery of the W and Z bosons two years later, an achievement for which the Nobel prize was awarded in 1984.

    Now an essential link in CERN’s accelerator complex, the energy of the SPS has been increased to 450 GeV and for 40 years the machine has been supplying various types of particles to dozens of different experiments, from the heavy-ion programme to studies of charge-parity violation (the imbalance between matter and antimatter) and of the structure of nucleons. At present, for example, it supplies particles to the COMPASS, NA61/Shine, NA62 and NA63 experiments, and it will shortly start sending protons to the new AWAKE project, which will test innovative acceleration techniques. The SPS also sends particles to test areas for equipment and detectors, including the HiRadMat project.

    Since 1989, when its big brother, the Large Electron-Positron Collider (LEP), was commissioned, the SPS has served as an injector, forming the last-but-one link in the accelerator chain. It supplied LEP with electrons and positrons until the end of 2000. It now accelerates protons and lead ions for the LHC, which replaced the LEP in the 27-kilometre tunnel.

    See the full article here.

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 11:24 am on June 17, 2016 Permalink | Reply
    Tags: Accelerator Science, , ,   

    From CERN: “First beam enters unique AWAKE experiment” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    17 Jun 2016
    Harriet Kim Jarlett

    CERN Awake schematic
    CERN Awake schematic

    2
    The team in the control room on the 16 June 2016 as the first beam of particles are sent through the proton beam line to the AWAKE experiment (Image: Ans Pardons/CERN)

    For the first time a beam of particles has been sent through the pioneering AWAKE experiment signaling the next stage of its commissioning.

    This is a test beam, meaning its purpose is to see whether all the parts of the beam line to the experiment are working correctly, and that the magnets are aligning the beam in the correct way.

    AWAKE (the Advanced Proton Driven Plasma Wakefield Acceleration Experiment) will be the first accelerator of its kind in the world. It is currently under construction, but hopes to test the concept that plasma wakefields driven by a proton beam could accelerate charged particles.

    The proton beam has to travel along around 800 m of proton beam line through the 10 m plasma cell, which at the moment is just an empty tube as the plasma is not filled yet, then downstream are several detectors.

    “What was really nice is that when we first sent the beam down the proton line to the experiment area, it immediately hit the last detector, verifying our calculations and installation. We can now move onto the next stage of commissioning. There is a strong and wonderful team behind this success,” explains Edda Gschwendtner, the project leader.

    The beam comes from CERN’s Super Proton Synchrotron (SPS), which just celebrated its fortieth birthday.

    CERN  Super Proton Synchrotron
    CERN Super Proton Synchrotron

    “Now we have to do the real work, checking all the details, but it’s great that the very first test showed everything is very consistent. Yes, now we have the beam but we still have to measure and calibrate everything, like the beam instrumentation along the beam line,” says Edda.

    AWAKE hopes to start collecting physics data by the end of the year. Next the team will finalise installation of the experiment, the laser and the full plasma cell.

    If it works this technology will mean linear colliders in the future could be much shorter, and even table-top accelerators could be possible.

    ILC schematic
    ILC schematic

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New

    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New II

    LHC

    CERN LHC Map
    CERN LHC Grand Tunnel

    CERN LHC particles

    Quantum Diaries

     
  • richardmitnick 11:51 am on June 15, 2016 Permalink | Reply
    Tags: Accelerator Science, , , BNL sPHENIX, , , ,   

    From BNL: “Introducing…sPHENIX!” 

    Brookhaven Lab

    June 15, 2016
    Karen McNulty Walsh

    1
    Members of the new sPHENIX collaboration at a meeting held at Brookhaven Lab in May 2016, with co-spokespersons Dave Morrison (green T-shirt, jeans) and Gunther Roland (blue shirt, black jeans) front and center.

    From the very beginning, there were hints that particle collisions at the Relativistic Heavy Ion Collider (RHIC) were producing something unusual. This U.S. Department of Energy (DOE) Office of Science User Facility at Brookhaven National Laboratory was designed to recreate the incredibly hot and dense conditions of matter in the early universe by colliding atomic nuclei at high enough energies to “melt” their constituent protons and neutrons. The collisions would “free” those particles’ inner building blocks—quarks and gluons—so nuclear physicists could study their behavior unbound from ordinary matter.

    Results from RHIC show that these particle smashups have indeed created a superhot primordial soup called “quark-gluon plasma” (QGP)—but one in which the quarks and gluons, though liberated from their protons and neutrons, continue to interact strongly. These strong interactions make the plasma flow like a nearly “perfect” liquid.

    RHIC’s discovery of the perfect liquid set off a decade-long and very successful effort to characterize its remarkable properties—both at RHIC and at Europe’s Large Hadron Collider (LHC), where physicists conduct complementary studies of quark-gluon plasma for a few weeks of each year. But understanding exactly how the QGP’s perfect fluidity and other collective properties emerge from its point-like constituent particles remains a compelling mystery.

    To address that mystery, a group of nuclear physicists has formed a new scientific collaboration that will expand on discoveries made by RHIC’s existing STAR and PHENIX research groups. This new collaboration, made up of veterans of the field and researchers just beginning their careers, has precise ideas about the measurements its members would like to make—and hopes of upgrading the PHENIX detector to make those measurements at RHIC.

    “What remains to be done is to understand how the QGP’s properties arise or emerge from the underlying quark and gluon interactions,” said Massachusetts Institute of Technology physicist Gunther Roland, a longtime RHIC and LHC collaborator and now a co-spokesperson for the new collaboration..

    Brookhaven physicist Dave Morrison, the other co-spokesperson, agrees: “On the one hand we have a very successful theory that describes the quarks and gluons as free point-like particles. On the other hand, we have a whole set of measurements that describe the collective properties of the QGP. What we’d like to do is connect the two—the microscopic to the not-so-microscopic.”

    For now, the collaboration goes by the name sPHENIX: “s” for its focus on the strongly interacting particles and PHENIX for the anticipated use of key detector components and that experiment’s location in the RHIC ring once the existing PHENIX systems complete their data-taking lifetime at the end of this year’s run. But the collaboration leaders emphasize that there’s no need for members to be previously affiliated with PHENIX—or indeed with prior research at RHIC.

    “This is a new collaboration, and, if we get the go-ahead for this upgrade, this detector will have brand new capabilities,” Morrison said.

    2
    A schematic of the proposed sPHENIX detector, showing several key components: outer and inner hadronic calorimeters (HCal), electromagnetic (EM) calorimeter, tracking systems, and coils of the superconducting solenoid magnet

    BNL/RHIC Phenix

    BNL/ Phenix
    BNL/ Phenix another view

    Tracking probes from within the plasma

    Figuring out how the QGP’s properties emerge from its smallest particles requires a detector that can make more—and more precise—measurements of what’s going on in the plasma at different length scales.

    “Think about looking at a pond that behaves like a liquid,” Morrison explained. “You might see waves and flowing water. If you had a microscope that could dial down, at some point you would see water molecules—the particles that make up the water. If you know a lot about those particles and how they behave, you can try to understand how the properties of the pond arise from the properties of the molecules. That’s what we’d like to do with the QGP.”

    Particle detectors are the microscopes nuclear physicists use to dive down into the details of subatomic matter. But instead of shining visible light, electrons, or x-rays on the sample, particle detectors pick up signals from particles created within the collisions. Measuring how these particles move through and lose energy by interacting with the plasma will reveal information about the QGP at scales between the level of individual quarks and the long-scale collective behavior.

    “There has to be an evolution from the short-wavelength behavior to the long-wavelength behavior, and we want to probe that transition,” Roland said.

    Fast detector for precision measurements

    One set of particles sPHENIX physicists are interested in tracking are upsilons—each made of two heavy quarks bound together. Each different bound state has a different mass. The sPHENIX scientists want to understand how upsilons with different masses form and disassociate and otherwise interact with the plasma.

    They’re also interested in analyzing collimated streams of particles called jets—created as the energy of individual fast-moving quarks and gluons is transformed into a cascade of new particles. Measuring how much energy is lost by higher- and lower-energy jets will convey information about both the individual particle scale deep within the plasma and its long-range characteristics.

    “The higher the momentum, the more rarely it is produced. So you need a very fast detector that can capture a lot of collisions to increase the chances of spotting these important events,” Roland said.

    By removing outdated components from PHENIX and replacing them with new, custom-designed systems, the sPHENIX collaboration would transform that experiment into a “new” state-of-the-art detector that can capture as many as 15,000 events per second—a significant increase over STAR’s current capture rate of 2,000 events per second, or PHENIX’s 5,000—with all the components needed to differentiate among the three mass states of upsilons and tease apart the full energy scale of jets.

    “This transformed detector would be suited to record a huge fraction of what RHIC can produce,” Morrison said.

    Testing essential detector components

    Physicists and engineers at Brookhaven and elsewhere have already begun building prototypes and testing components that could be used to achieve the anticipated transformation. And this endeavor is attracting a new generation of physicists eager to get in on the ground floor of a new experiment.

    “I worked on PHENIX as grad student at Stony Brook University. Then, as a postdoc at Yale, I worked on the ALICE experiment at the LHC,” said Megan Connors, a RIKEN-BNL Research Center Fellow at Brookhaven Lab who will begin teaching and forming her own research group at Georgia State University next year. “When I came on the scene, both colliders were already up and running. So this is a chance to be involved from the start—to see how these experiments come to life, to be part of the formation of the collaboration and get involved in building the hardware in addition to analyzing the data.”

    3
    Megan Connors and Anne Sickles checking out calorimeter components at Brookhaven Lab.

    The piece of hardware that currently has her attention is a prototype “calorimeter” that would track and reconstruct the sprays of particles that make up jets, which recently underwent extensive testing at Fermi National Accelerator Laboratory.

    “A typical jet may contain 10 or 15 particles, but you need to tease those out from the hundreds of particles coming out of a heavy ion collision event,” Connors said. “And you need to capture all the particles to be able to reconstruct the jet and see how much energy it loses as it travels through the plasma.”

    You also need to know how much energy the jet had to start with. Most of the time jets are formed in back-to-back pairs. Both jets lose energy in the plasma. However sometimes, instead, a particle of light called a photon gets produced back-to-back with a jet. But unlike the jet particles, the photon shooting off in the opposite direction does not interact with the quarks and gluons in the plasma, so it doesn’t lose any energy.

    “If you have a photon going one way, and a jet going the other way, the jet and the photon had the same starting energy,” explained Anne Sickles, an sPHENIX collaborator from the University of Illinois at Urbana-Champaign who was also involved in the calorimeter design and testing. “So measuring the photon’s energy gives you the starting point. Measuring the particles that make up the jet and subtracting from the photon energy tells you how much energy the jet lost.”

    Using Fermilab’s Test Beam Facility, Sickles and some of her students shot a beam of electrons through portions of an “electromagnetic” calorimeter they designed to track photons and some of the other particles that make up jets. For the initial tests, the electrons—pure electromagnetic particles like photons—served as stand-ins for the photons. The aim of the tests was to be sure all areas of the detector respond in a similar way, and that there’s no variation between pieces built by Sickles and her students in Illinois and pieces constructed by an outside contractor.

    Next, the physicists added components of a “hadronic” calorimeter for tracking hadrons (particles made of more than one quark), which Connors and her team had been working on. They placed the hadron detectors directly behind the electromagnetic calorimeter—just as the two components will be arranged in the actual detector. This outer layer is designed to catch the larger hadron particles that make it through the first layer so physicists can account for the full energy of each jet.

    Building the calorimeter thick enough to “catch” all the particles is one way that the design of sPHENIX benefits from the 16 years of operating RHIC and several years experience at LHC.

    “Before RHIC was built, we didn’t even know how many particles would be produced. We had to build the detectors to cover a wide range of possibilities,” Morrison said. “Now, knowing what the collisions look like and the kinds of particles produced, we can build a detector tailored to do the measurements that are focused on the specific important questions we’d like to answer.”

    Mighty magnet

    Testing is also underway on a 20-ton solenoid magnet acquired from a former physics experiment at DOE’s SLAC National Accelerator Laboratory. This magnet would form the heart of the sPHENIX detector, completely surrounding the collision zone like the cylindrical magnet at the center of RHIC’s STAR detector. Like STAR’s, the sPHENIX magnet would bend the trajectories of charged particles as they emerge from the collisions. But with three times the bending power of STAR, sPHENIX should be able to separate out the signals from the three types of upsilon particles, whose masses differ by only a few percent.

    “Upsilons don’t make it all the way to the magnet,” Morrison explained. “These are heavy particles that decay, often into an electron and an antielectron, which have a lot of energy when they come out. You need a powerful magnetic field to bend these charged particles so you can get a better measurement of their velocity and momentum, and tease out small differences to separate the electrons that come from the different-size upsilons.”

    So far, a team of engineers and physicists in Brookhaven’s Superconducting Magnet Division, Collider-Accelerator Department, and Physics Department has cooled the superconducting magnet down to its near-absolute-zero operating temperature of 4.2 Kelvin and tested it with 100 amperes of current.

    “We needed to test the overall health and integrity of the magnet to make sure all the joints and couplings are in place, in case they got jostled while being transported cross-country,” said lead magnet engineer Piyush Joshi. They also tested systems Joshi designed to shut the magnet down in a controlled manner if the field between the magnet’s two layers of coils ever gets out of balance. “You want to detect any imbalance very quickly so you can extract the energy before it causes any damage to the magnet,” he said. He originally wrote the algorithms for an LHC magnet project, but they proved to be just as useful for the sPHENIX tests.

    With the initial, low-field tests complete, the group will next use steel recycled from another older experiment at Brookhaven to surround the magnet to contain its most powerful field—and ramp it up to a full 4,600 amps.

    5
    Engineers and physicists involved in testing the 20-ton superconducting solenoid expected to form the heart of the sPHENIX upgrade: Kin Yip, Collider-Accelerator Department (CAD); Piyush Joshi, Superconducting Magnet Division (SMD); Richard Meier, CAD cryo group; Brian Van Kuik, CAD main control room operations coordinator; Ray Ceruti, SMD; Sonny Dimaiuta, SMD; Dominick Milidantri, SMD.

    Path forward

    By reusing equipment and tools developed with funding for RHIC and the LHC, and inspiring university collaborators to chip in their expertise, the nascent collaboration has taken these early steps on the path toward transforming PHENIX into sPHENIX. But the team hopes to get an official seal of approval—and, eventually, a budget—from DOE.

    The 2015 Long Range Plan for Nuclear Science—a set of recommendations made by the nation’s Nuclear Science Advisory Committee to leaders at DOE and the National Science Foundation—identifies the sPHENIX “state-of-the-art jet detector” as “essential” to probing the inner workings of QGP at shorter and shorter length scales, one of two “central goals” noted in the report for completing the scientific mission at RHIC. The report also notes that there is significant international interest in sPHENIX.

    “Right now we have a collaboration of 183 people, and growing,” Morrison said, with those scientists representing 58 institutions in 10 countries.

    Looking ahead and continuing the tradition of making the most of our nation’s investments in science, the physicists designing the sPHENIX upgrades say this transformed detector could largely be reused as a detector for a future Electron Ion Collider—the next priority nuclear physics project identified in the Long Range Plan.

    “Transforming PHENIX into sPHENIX would maximize the benefits derived from the investments already made to build RHIC by allowing us to fully understand the quark-gluon plasma,” Morrison said. “It’s what we need to do to complete the story of QGP discovery and to prepare for the coming research directions in nuclear physics.”

    sPHENIX R&D is supported by the DOE Office of Science and also by Brookhaven Lab’s Laboratory Directed Research and Development program, BNL Program Development, and in-kind contributions from collaborating universities.

    See the full article here .

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    BNL Campus

    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), 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.
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  • richardmitnick 2:47 pm on June 8, 2016 Permalink | Reply
    Tags: Accelerator Science, , FNAL FAST, New beginning at FAST: Research accelerator reaches design beam energy   

    From FNAL: “New beginning at FAST: Research accelerator reaches design beam energy” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    June 8, 2016
    Leah Hesla

    1
    Fermilab accelerator scientist Jinhao Ruan (center) shows Fermilab Director Nigel Lockyer (left) the laser setup for the FAST photoinjector. Vladimir Shiltsev (right) is director of the Fermilab Accelerator Physics Center. Photo: Reidar Hahn

    On May 16, Fermilab sent an electron beam with an energy of 50 million electronvolts, or MeV, through the photoinjector at the Fermilab Accelerator Science and Technology facility (FAST), achieving a major design goal for the accelerator – and marking the beginning of a new accelerator science program at the laboratory.

    1
    FNAL FAST

    “This is a major milestone for our general accelerator R&D,” said Vladimir Shiltsev, head of the Fermilab Accelerator Physics Center. “The delivery of this beam marks the start of a new program here – new facility, new science capabilities,” Shiltsev said.

    The delivery of 50-MeV beam is the first step in establishing an accelerator R&D facility that will serve as one of America’s leading test beds for cutting-edge, record-high-intensity particle beam research. Once complete, FAST will provide scientists and engineers from around the world with a place to study the science of high-intensity particle beams and superconducting radio-frequency acceleration, the technology on which nearly all future high-energy accelerators are based.

    The photoinjector is just the first phase of a larger accelerator to be built at FAST, which is supported by the DOE Office of Science. It will include a superconducting linear accelerator and a particle storage ring called the Integrable Optics Test Accelerator, or IOTA, which will be built over the next two years.

    Although the photoinjector is just the front section of what will become a higher-energy accelerator, it still provides enough beam to be useful for carrying out scientific research. In fact, the first accelerator physics researchers to sign up for time at the facility have now begun using the electron beam. The inaugural group, led by Northern Illinois University professors Philippe Piot and Swapan Chattopadhyay, has reserved two months of beam time as part of the Fermilab-NIU Research Cluster.

    For FAST to produce the kinds of beams that are useful for accelerator R&D, its initial electron beam had to have an energy of 50 MeV. In 2015, Fermilab delivered a 20-MeV electron beam. Since then, scientists, engineers and technicians have upgraded the photoinjector to meet specifications, including installing a refurbished accelerating cavity that had been used elsewhere on the Fermilab site.

    “It takes a significant effort to install all the complex components and subsystems that make up such an accelerator, and everything has to be done just right,” said Jerry Leibfritz, project engineer for FAST. “The fact that both 20-MeV and 50-MeV beams were achieved within a day or two of the start of commissioning is truly a testament to the excellent work and dedication of all those involved in this project.”

    In the current setup, electron bunches generated by a laser are accelerated through two superconducting accelerating cavities (including the refurbished cavity), which bring the energy of electrons to 50 MeV.

    As work on FAST progresses, the electron beam will continue through another eight superconducting radio-frequency cavities, accelerating to 300 MeV before entering the beamline for IOTA.

    “FAST represents the beginning of a new era at Fermilab, in which the study and development of high-intensity particle beams become an important and productive part of the laboratory program,” said Fermilab Director Nigel Lockyer.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

     
  • richardmitnick 3:34 pm on May 22, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , , ,   

    From HuffPost: “Meet The Most Powerful Woman In Particle Physics” Women in Science 

    Huffington Post
    The Huffington Post

    05/18/2016
    David Freeman

    1
    Fabiola Gianotti, CERN’s new director-general. Christian Beutler

    Fabiola Gianotti isn’t new to CERN, the Geneva, Switzerland-based research organization that operates the Large Hadron Collider (LHC), the world’s biggest particle collider.

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

    In fact, the Italian particle physicist was among the CERN scientists who made history in 2012 with the discovery of the Higgs boson.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN/CMS Detector
    CERN/CMS Detector

    But now Gianotti isn’t just working at CERN. As the organization’s new director-general — the first woman ever to hold the position — she’s running the show. And though expanding our knowledge of the subatomic realm remains her main focus, she’s acutely aware that she is now a high-visibility role model for women around the world.

    “Physics is widely regarding as a male-dominated field, and it’s true that there are more men in our community than women,” Gianotti told The Huffington Post in an email. “So I am glad if in my new role I can contribute to encourage young women to undertake a job in scientific research with the certitude that they have the same opportunities as men.”

    Recently, HuffPost Science posed a few questions to Gianotti via email. Here, lightly edited, are her answers.

    How will things be different for you in your new role?

    My new role is very interesting and stimulating, and I feel very honored to have been offered it. The range of issues I have to deal with is much broader than before and includes scientific strategy and planning, budget, personnel aspects, relations with a large variety of stakeholders, etc. Days are long and full, and I am learning many new things. And there is nothing more enriching and gratifying than learning.

    What’s a typical day like for you?

    Super-hectic, super-speedy and … atypical!

    What do you think explains the gender gap in science generally and in physics particularly?

    There are many factors. There’s no difference in ability between men and women, that’s for sure. And in my experience, the more diverse a team is, the stronger it is. There is the baggage of history, of course, which takes a long time to overcome. There is the question of the lack of role models, and there is the question of making workplaces more family friendly. We need to enable parents, men or women, to take breaks to raise families and we need to support parents with infrastructure and facilities.

    2
    The Large Hadron Collider, Geneva, Switzerland.

    Your term as CERN’s director-general is scheduled to last five years. What are your goals for CERN during this period?

    The second run of the LHC is the top priority for CERN in the coming years. We got off to a very good start in 2015, and have three years of data-taking ahead of us before we go into the accelerator’s second long shutdown. The experiments are expected to record at least three times more data than in Run 1 at an energy almost twice as large. It will be a long time before another such step in energy will be made in the future.

    So, the coming years are going to be an exciting period for high-energy physics. But CERN is not just the LHC. We have a variety of experiments and facilities, including precise measurements of rare decays and detailed studies of antimatter, to mention just a couple of them. In parallel with the ongoing program, we will be working to ensure a healthy long-term future for CERN, at first with the high-luminosity LHC upgrade scheduled to come on stream in the middle of the next decade, and also through a range of design studies looking at the post-LHC era — from 2035 onwards.

    CERN HL-LHC bloc

    What discoveries can we reasonably expect from CERN during your term?

    I’m afraid that I don’t have a crystal ball to hand. There will be a wealth of excellent physics results from the LHC Run 2 and from other CERN experiments. We’ll certainly get to know the Higgs boson much better and expand our exploration of physics beyond the Standard Model.

    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.

    Whether we find any hints of the new physics everyone is so eagerly waiting for, however, I don’t know. We know there’s new physics to be found. Good as it is, the Standard Model explains only the 5 percent of the universe that is visible. There are so many exciting questions still waiting to be answered.

    What are the biggest opportunities at CERN? The biggest challenges?

    These two questions have a single answer. Over the coming years, the greatest opportunities and challenges, not only for CERN but for the global particle physics community as a whole, come from the changing nature of the field. Collaboration between regions is growing. CERN recently signed a set of agreements with the U.S. outlining U.S. participation in the upgrade of the LHC and CERN participation in neutrino projects at Fermilab in the U.S.

    FNAL LBNF/DUNE
    FNAL LBNF/DUNE

    There are also emerging players in the field, notably China, whose scientific community has expressed ambitious goals for a potential future facility. All this represents a great opportunity for particle physics. The challenge for all of us in the field is to advance in a globally coordinated manner, so as to be able to carry out as many exciting and complementary projects as possible.

    Were you always interested in being a scientist? If you couldn’t be a scientist, what would you be/do?

    I was always interested in science, and I was always interested in music. I pursued both for as long as I could, but when the time came to make a choice, I chose science. I suppose that as a professional physicist, it is still possible to enjoy music — I still play the piano from time to time. But as a professional musician, it would be harder to engage in science.

    What do you do in your spare time?

    I spend my little spare time with family and friends. I do some sport, I listen to music, I read.

    What do you think is the biggest misconception nonscientists have about particle physics?

    That it’s hard to understand! Of course, if you want to be a particle physicist, you have to master the language of mathematics and be trained to quite a high level. But if you want to understand the field conceptually, it’s almost child’s play. All children are natural scientists. They are curious, and they want to take things apart to see how they work.

    Particle physics is just like that. We study the fundamental building blocks of matter from which everything is made, and the forces at work between them. And the equations that describe the building blocks and their interactions are simple and elegant. They can be written on a small piece of paper.

    See the full article here .

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  • richardmitnick 8:28 am on May 22, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , , ,   

    From livescience: “LHC [Particle] Smasher Opens Quantum Physics Floodgates” 

    Livescience

    May 20, 2016
    Ian O’Neill, Discovery News

    1
    A display of a proton-proton collision taken in the LHCb detector in the early hours of May 9.
    Credit: CERN/LHCB

    CERN/LHCb
    CERN/LHCb

    A display of a proton-proton collision taken in the LHCb detector in the early hours of May 9. Credit: CERN/LHCb

    The Large Hadron Collider is the most complex machine ever built by humankind and it is probing into deep quantum unknown, revealing never-before-seen detail in the matter and forces that underpin the foundations of our universe.

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

    In its most basic sense, the LHC is a time machine; with each relativistic proton-on-proton collision, the particle accelerator is revealing energy densities and states of matter that haven’t existed in our universe since the moment after the Big Bang, nearly 14 billion years ago.

    The collider, which is managed by the European Organization for Nuclear Research (CERN) is located near Geneva, Switzerland.

    With the countless billions of collisions between ions inside the LHC’s detectors comes a firehose of data that needs to be recorded, deciphered and stored. Since the 27 kilometer (17 mile) circumference ring of supercooled electromagnets started smashing protons together once more after its winter break, LHC scientists are expecting a lot more data this year than what the experiment produced in 2015.

    “The LHC is running extremely well,” said CERN Director for Accelerators and Technology Frédérick Bordry in a statement. “We now have an ambitious goal for 2016, as we plan to deliver around six times more data than in 2015.”

    And this data will contain ever more detailed information about the elusive Higgs boson that was discovered in 2012 and possibly even details of “new” or “exotic” physics that physicists could spend decades trying to understand. Key to the LHC’s aims is to attempt to understand what dark matter is and why the universe is composed of matter and not antimatter.

    In fact, there was already a buzz surrounding an unexpected signal that was recorded in 2015 that could represent something amazing, but as is the mantra of any scientist: more data is needed. And it looks like LHC physicists are about to be flooded with the stuff.

    Central to the LHC’s recent upgrades is the sheer density of accelerated “beams” of protons that are accelerated to close to the speed of light. The more concentrated or focused the beams, the more collisions can be achieved. More collisions means more data and the more likelihood of revealing new and exciting things about our universe. This year, LHC engineers hope to magnetically squeeze the beams of protons when they collide inside the detectors, generating up to one billion proton collisions per second.

    Add these advances in extreme beam control with the fact the LHC will be running at a record-breaking collision energy of 13 TeV and we have the unprecedented opportunity to make some groundbreaking discoveries.

    “In 2015, we opened the doors to a completely new landscape with unprecedented energy. Now we can begin to explore this landscape in depth,” said CERN Director for Research and Computing, Eckhard Elsen.

    The current plan is to continue proton-proton collisions for six months and then carry out a four-week run using much heavier lead ions.

    So the message is clear: Hold onto your hats. We’re in for an incredible year of discovery that could confirm or deny certain models of our universe and revel something completely unexpected and, possibly, something very exotic.

    See the full article here .

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  • richardmitnick 11:07 am on May 19, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , The Biggest Hopes Of What A New Particle At The LHC Might Reveal   

    From Ethan Siegel: “The Biggest Hopes Of What A New Particle At The LHC Might Reveal” 

    Starts with a Bang

    May 18, 2016
    Ethan Siegel

    1
    Inside the magnet upgrades on the LHC, that have it running at nearly double the energies of the first (2010-2013) run. Image credit: Richard Juilliart/AFP/Getty Images.

    Built over an 11-year period from 1998 to 2008, the Large Hadron Collider was designed with one goal in mind: to create the greatest numbers of the highest-energy collisions ever, in the hopes of finding new fundamental particles and of revealing new secrets of nature.

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

    Over a three year period from 2010 to 2013, the LHC collided protons together at energies nearly four times the previous record, with an upgrade nearly doubling that in 2015: to a record 13 TeV, or approximately 14,000 times the energy inherent to a proton via Einstein’s E = mc^2. The largest, most advanced detectors of all — CMS and ATLAS — were built around the main two collision points, collecting as precise and accurate data about all the debris that emerges each time two protons smash together.

    CERN/CMS Detector
    CERN/CMS detector

    CERN/ATLAS detector
    CERN/ATLAS detector

    July 2012 was a watershed moment for particle physics, as enough high-energy collisions were reconstructed to definitively announce, in both detectors, the first concrete, direct evidence for the Higgs Boson: the last undiscovered particle in the Standard Model of particle physics.

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    CERN CMS Higgs Event
    CERN CMS 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

    3
    Image credit: The CMS Collaboration, “Observation of the diphoton decay of the Higgs boson and measurement of its properties”, (2014). This was the first “5-sigma” detection of the Higgs.

    But that was expected. The problem is, there are a whole host of questions about the Universe that the Standard Model of particle physics doesn’t answer at a fundamental level, including:

    Why is there more matter than antimatter in the Universe?
    What is dark matter, and what particle(s) beyond the Standard Model (which cannot account for it) explains it?
    Why does our Universe have dark energy, and what is its nature?
    Why don’t the strong interactions in the Standard Model exhibit CP-violation in the strong decays?

    Why do neutrinos have such small but non-zero masses compared to all the other particles?
    And why do the Standard Model particles have the properties and masses that they do, and not any others?

    And the great hope of the LHC, the real hope, is that we’ll learn something extra, beyond the Standard Model, that helps answer one or more of these questions.

    4
    The particles of the Standard Model, all of which have been detected. Image credit: E. Siegel, from his new book, Beyond The Galaxy.

    With the possible exception of dark energy, all of these problems pretty much require new fundamental particles to explain them. And many of them — the dark matter problem, the matter/antimatter problem, and the mass-of-the-particles problem (a.k.a. the Hierarchy problem) — may actually be within reach at the LHC. One way to look for this new physics is to look for deviations from the expected (and well-calculated) behavior in the decays and other properties of the known, detectable Standard Model particles. So far, to the best of our abilities, everything falls within the “normal” range, where things are perfectly consistent with the Standard Model.

    6
    Image credit: The ATLAS collaboration, 2015, of the various decay channels of the Higgs. The parameter mu = 1 corresponds to a Standard Model Higgs only. Via https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/CONFNOTES/ATLAS-CONF-2015-007/.

    But the second way is even better: to discover, directly, evidence for a new particle beyond the Standard Model. As the LHC begins collecting even higher-energy data and with even greater numbers of collisions-per-second, it’s in the best position it’s ever going to be to find new fundamental particles; particles it never expected to find. Of course, it doesn’t exactly find particles; it finds the decay products of particles! Fortunately, because of how physics works, we can reconstruct what energy (and hence, what mass) those particles were created at, and whether we’ve got a new particle after all. At the end of the LHC’s initial run, there’s an intriguing (but not certain) hint of what might be a new particle. This “750 GeV diphoton bump” might not be real, but if it is, it could mean the world to physicists everywhere.

    7
    The ATLAS and CMS diphoton bumps, displayed together, clearly correlating at ~750 GeV. Image credit: CERN, CMS/ATLAS collaborations, image generated by Matt Strassler at https://profmattstrassler.com/2015/12/16/is-this-the-beginning-of-the-end-of-the-standard-model/.

    The preliminary signal is discernible in both the CMS and the ATLAS detectors so far, and that makes the possibility extra tantalizing. Within about 6 more months, we should know whether this signal is strengthening — and hence likely real — or whether it shows itself to be spurious. If it’s real, here are some of the top possibilities:

    1. It’s a second Higgs boson! Many extensions to the Standard Model — like supersymmetry — predict additional Higgs particles that are heavier than the current (126 GeV) one we know. If so, this could be a window into a whole world of physics beyond the Standard Model, including into the matter/antimatter asymmetry and the Hierarchy problem.
    2. It’s dark matter-related. Could this new particle be a window into the dark sector? Is there some energy non-conservation happening here that means we’re making something that the detectors can’t see? This is one of the “dare-to-dream” possibilities of particle physics: that the LHC could create dark matter. There’s even a fun little correlation here with something most people haven’t put together: there’s an excess in cosmic ray energies seen in this exact same energy range from the balloon-borne Advanced Thin Ionization Calorimeter (ATIC) experiment!

    8
    Image credit: J. Chang et al. (2008), Nature, from the Advanced Thin Ionization Calorimeter (ATIC).

    3.It’s a window into extra dimensions. If there are more than the three spatial dimensions we’re used to, especially at smaller scales, new particles can arise in our three dimensions as a result. These Kaluza-Klein particles could show up at the LHC, and might decay to two photons. Studying how they decay could tell us whether this is true.

    4.It’s a new part of the neutrino sector. This would be a little unusual — since neutrinos don’t normally decay to two photons; they’ve got the wrong spin — but a scalar neutrino could create two photons, which is actually a thing in Standard Model extensions. The couplings and decay pathways, if it’s real, could show us this.

    5. It’s a composite particle. The first particle we ever saw decay into two photons was the lightest quark-antiquark combination of all: the neutral pion. Perhaps these Standard Model particles are combining in ways we don’t yet understand, and what we’ve found is nothing new.
    Or, most excitingly, none of the above. The most exciting discoveries are the ones you never anticipated, and perhaps it isn’t any of the speculative scenarios we know to look for. Perhaps nature is more surprising than even our wildest theoretical dreams.

    6. Or, most excitingly, none of the above. The most exciting discoveries are the ones you never anticipated, and perhaps it isn’t any of the speculative scenarios we know to look for. Perhaps nature is more surprising than even our wildest theoretical dreams.

    The answers, believe it or not, are locked inside of the smallest particles in nature. All we need are the highest energies we can get to in order to find out.

    Of course, this could simply turn out to be a statistically insignificant bump that goes away with more data; it may be nothing at all. This has already happened once before, at about three times the energy. There was hint of an extra “bump” at just over 2 TeV in both detectors, as you can see for yourself.

    7
    Images credit: ATLAS collaboration (L), via http://arxiv.org/abs/1506.00962; CMS collaboration (R), via http://arxiv.org/abs/1405.3447.

    A reanalysis of the data shows there’s no significance to this signal, and that might be what we have in the 750 GeV case, too. But the possibility that it’s real is too big to ignore, and the data will come in to tell us by the end of this year. The biggest unanswered, fundamental questions in theoretical physics will get a run for the money, and all it takes is for a bump in the data to hold up a little bit longer.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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