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  • richardmitnick 7:00 am on December 3, 2016 Permalink | Reply
    Tags: , , , , In Practice: What do data analysts do all day?, , Particle Physics, , The appeal of the unknown   

    From CERN: “In Practice: What do data analysts do all day?” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    2 Dec 2016
    Kathryn Coldham
    Kate Kahle
    Harriet Jarlett

    1
    CMS physicist Nadjieh Jafari switched from theoretical to experimental physics early on in her career. “It was an easy decision,” she says. “Once I saw CERN, it became my quest.” (Image: Sophia Bennett/ CERN)

    Another day, another mountain of data to analyse. In 2016, CERN’s Large Hadron Collider produced more collisions than in all previous years of operation put together. Experimental physicists spend much of their professional lives analysing collision data, working towards a potential discovery or to sharpen our picture of nature. But when the day-to-day findings become predictable, do physicists lose motivation?

    What if there’s nothing there?

    CERN has made headlines with its discoveries, but does this mean today’s researchers are just seeking fame and fortune? For most, being front-page news is not what stokes their physics passion, as they stare at their computer screens for hours. Instead, it’s the knowledge and excitement of understanding our universe at the most fundamental level.

    Siegfried Foertsch, run coordinator of the ALICE experiment, is motivated by “the completely new discoveries that lie around the corner. They’ve become ascertainable because of the new energies that the LHC machine is providing.”

    2
    Sitting in the ALICE control room, Siegfried explains: “I think what motivates people in these experiments is that you are entering terra incognita, it’s completely new science. It drives most people in these big experiments, it’s about new discoveries.” (Image: Sophia Bennett/CERN)

    These headline-worthy discoveries are rare. Instead, researchers make small, incremental findings day-by-day. “It doesn’t bother me that it’s not going to make front-page news. I know that within the particle physics community the research is important and that’s enough,” says Sneha Malde of the LHCb experiment.

    For CMS physicist Anne-Marie Magnan, her colleagues provide the much-needed push.

    “We have deadlines, so if you are part of an analysis you have pressure to make progress and you put personal pressure on yourself because you want to see the result. If you’re on a review committee you have deadlines, you need to provide feedback, the same if you’re managing a subgroup, you’re responsible for the group to show results at conferences. So you push people and they push you back to try and make progress,” she explains.

    Magnan analyses data to search for Higgs bosons . She describes her daily work as “programming, mostly. A lot of interaction with people, I have students to Skype with and when they say ‘I’m stuck, I don’t know what to do’ we chat and find solutions. At some points I’ve been a subgroup convener. There you encourage people to make progress and provide feedback on their analyses.”

    “It’s an exercise of patience because, after time, the incremental findings lead to a result. And even if you’re just working towards a result, you still have to solve technical problems each day,” explains Leticia Cunqueiro Mendez, a senior postdoctoral researcher working with the ALICE detector.

    Building bonds: the road to success

    Each one of these incremental, small discoveries are documented by a research paper. At CERN, these papers are often authored by hundreds, even thousands of people, as was the case with the papers announcing the Higgs discovery. And they aren’t just experimental physicists; students, technicians, engineers and computer scientists are all often equally involved.

    Having a high level of motivation can only get a physicist so far, working with others is the route to success.

    “People need each other here,” says Siegfried Foertsch, “the idea of a physicist without an engineer at CERN is unthinkable, and similarly vice versa. It’s symbiotic.”

    “I think the work of the technicians is a major contribution to the applied physics that I’m involved in. They are the unsung heroes in most of what we do to some extent,” says David Francis, Project Leader of the ATLAS Trigger and Data Acquisition System.

    For Cunqueiro Mendez, “the main thing is to know the possibilities of your detector and to have an interesting idea of what physics might be observable. For this you need interaction with the theorists so, in principle, you have to be reading papers and attending conferences. Here at CERN, you can meet your theory colleagues for a coffee and discuss your possibilities.”

    Eeney meeney miney mo

    Working with others can be collaborative, but it can also be competitive. There is a point of pride for one experiment to beat the competition to a discovery.

    3
    Sneha Malde standing in the corridor outside of her office (Image: Maximilien Brice/CERN)

    While the ATLAS and CMS experiments perform similar searches, the LHCb and ALICE experiments have particular fields of study, and the work that the associated physicists do differs as a result.

    Bump searches are what physicists call it when they try to find statistically significant peaks in the data; the presence of a bump could indicate the existence of a new particle. Some of these searches are done at ATLAS and CMS, where new particles are the name of the game. At LHCb and ALICE they try to take precision measurements of phenomenon, more than particles.

    “I don’t think I would be very happy just looking at empty plots with nothing in them, which could happen in bump searches if they don’t find anything new,” muses Malde. “I like the precision measurement aspect of LHCb’s data.”

    Studying and searching for different things means the data plots for different experiments look very different.

    “I like having obvious things in my plots. I like nice bumps, big ones. We have lots of bumps that don’t disappear, and they are really big peaks. We don’t have bumps, we have mountains!” – Sneha Malde, LHCb data analyst

    ATLAS physicist Anatolli Romaniouk, marvels at this range of LHC experiments. They “embrace an incredible field of physics, they search for everything.”

    “This is physics; if we know what we are searching for, then we don’t need experiments. If you know what exactly you want to find, it’s already found, or will be found soon. That’s why our experiments are beautiful because these experiments embrace an incredible field of physics, the LHC, it searches for everything,” explains Romaniouk.

    The beauty of the unknown

    4
    ATLAS physicist Anatolli Romaniouk has worked at CERN since 1990. The students he sees in the collaboration “know a bit of electronics, data acquisition and data analysis, very often they do it from second year of university and this is interesting. I find this brilliant, that they practice real physics at an early stage of their education.” (Image: Sophia Bennett/CERN)

    The appeal of the unknown, the as yet undiscovered, ignites the curiosity in the physicists and fuels them in their analyses.

    “When you have something in theory and think that it could be real – that it could exist – then you start to really think how you can look for it and try to find it,” says CMS physicist Nadjieh Jafari. “You build your experiment based on the theories. The CMS’s muon system was perfectly designed to discover the Higgs boson but at the moment of designing it, it was just an idea that we might find it. For me, that’s the most beautiful part of what we do.”

    See the full article here.

    Please help promote STEM in your local schools.

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    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 12:54 pm on November 30, 2016 Permalink | Reply
    Tags: , , , MicroBooNE, , , Particle Physics   

    From FNAL: “Handy and trendy: MicroBooNE’s new look” 

    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.

    November 30, 2016
    Ricarda Laasch

    1
    MicroBooNE’s shiny new exterior helps scientists identify cosmic rays masquerading as neutrinos. From left: Elena Gramellini, Thomas Mettler. Martin Auger, Mark Shoun, John Voirin. Photo: Reidar Hahn

    The signals of cosmic rays

    Cosmic rays are a constant rain of particles that are created in our sun or faraway stars and travel through space to our planet.

    They’re subjects of many important physics studies, but for MicroBooNE’s research, they simply get in the way. That’s because MicroBooNE scientists are looking for something else — abundant, subtle particles called neutrinos.

    FNAL/MicrobooNE
    FNAL/MicrobooNE

    Unlocking the secrets neutrinos hold could help us understand the evolution of our universe, but they’re exceedingly difficult to measure. Fleeting neutrinos are rarely captured, even as they sail through detectors built for that purpose.

    Add to that the fact that their interactions are potentially drowned in a sea of cosmic rays rushing through the same detector, and you get a sense of the formidable challenge that neutrinos represent.

    The MicroBooNE experiment starts with Fermilab’s powerful accelerators, which create neutrino beams that are then propelled through the MicroBooNE detector.

    2
    July 8, 2015 Fermilab’s Main Injector accelerator, one of the most powerful particle accelerators in the world, has just achieved a world record for high-energy beams for neutrino experiments. Photo: Fermilab

    3

    4
    Fermilab’s accelerator complex comprises seven particle accelerators and storage rings. It produces the world’s most powerful, high-energy neutrino beam and provides proton beams for a variety of experiments and R&D programs.

    Fermilab is currently upgrading its accelerator complex to deliver high-intensity neutrino beams and to provide beams for a broad range of new and existing experiments, including the Long-Baseline Neutrino Experiment, Muon g-2 and Mu2e.

    “The neutrino beam here at the lab gives us the right conditions to study neutrinos,” said Elena Gramellini, a Yale University graduate student on the MicroBooNE experiment. “Our challenge is to pick out neutrinos from many cosmic rays passing through the detector.”

    Since cosmic rays are made of some of the same particles produced when a neutrino interacts with matter, they leave signals in the MicroBooNE detector that are often similar to the sought-after neutrino signals. Scientists need to be able to sort the cosmic rays in the MicroBooNE data from the neutrino signals.

    Tagging and sorting

    Even several feet of concrete enclosure would not completely block cosmic rays from hitting a detector such as MicroBooNE, not to mention that such a structure would be inconvenient and expensive. Instead, MicroBooNE uses the aforementioned panels, called a cosmic ray tagger, or CRT. While the panels don’t block cosmic rays, they do detect them.

    Each CRT panel has particle-detecting components – strips of scintillator – that lie beneath its shiny aluminum enclosure. Cosmic ray particles can easily pass through aluminum and the scintillator — a clear, plastic-like material — on their way toward the MicroBooNE detector.

    The cosmic ray particles deposit energy in the plastic scintillator, which then emits light. An optical fiber buried inside the scintillator captures the emitted light and transmits it to devices that generate the digital information that tells scientists where and when the cosmic ray struck.

    “With our current layout of scintillator strips in each panel, we are able to tell precisely where the cosmic ray enters the MicroBooNE detector after it left the panel,” said Igor Kreslo, professor at the University of Bern who designed the CRT panels for MicroBooNE. “Our design effort really paid off and now ensures thorough cosmic ray tracking.“

    So why the shiny aluminum shell? It blocks unwanted light from the detector’s immediate surroundings so that only light created by cosmic rays inside a CRT panel reaches the optical fiber and is detected.

    Putting up panels

    The 49 rectangular CRT panels are the contribution of the University of Bern in Switzerland, one of the 28 institutions collaborating on MicroBooNE worldwide. They produced the panels last winter and shipped them to Fermilab during the spring.

    “This was a large project for us, and it took everyone in Bern to finish everything in time,” said Martin Auger, scientist at the University of Bern who planned the arrangement of the CRT panels. “A key moment was the test of the CRT panels after the long journey to Fermilab. All the panels arrived in good shape!”

    The installation team overcame a number of challenges —including the tight space in which MicroBooNE stands — to successfully place the panels around the detector.

    “The installation crew is a crack team of veteran Fermilab employees,” said John Voirin, who leads experiment installations at the laboratory. “In the end we have a very elegant, safe operating product that is a valuable asset to the experiment.”

    Later this year the group will complete the installation by placing the final layer on top of the MicroBooNE detector. Even without it, the CRT already greatly enhances the capabilities of the experiment.

    “We started taking data just in time for the first neutrinos delivered to the experiment,” Gramellini said.

    See the full article here .

    Please help promote STEM in your local schools.

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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 12:37 pm on November 29, 2016 Permalink | Reply
    Tags: , , , , Particle Physics   

    From Don Lincoln at FNAL: Higgs Boson 2016 Video 

    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.

    FNAL Don Lincoln
    From Don Lincoln of FNAL

    Published on Nov 16, 2016

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    The Higgs boson burst into the public arena on July 4, 2012, when scientists working at the CERN laboratory announced the particle’s discovery. However the initial discovery was a bit tentative, with the need to verify that the discovered particle was, indeed, the Higgs boson. In this video, Fermilab’s Dr. Don Lincoln looks at the data from the perspective of 2016 and shows that more recent analyses further supports the idea that the Higgs boson is what was discovered.

    Watch, enjoy, learn.

    The data presented in this video can be seen in a technical form in this paper: http://cds.cern.ch/record/2158863/fil…. Figure 19 is a more accurate version.

    See the full article here .

    Please help promote STEM in your local schools.

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    FNAL Icon
    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 1:28 pm on November 28, 2016 Permalink | Reply
    Tags: Bolometers, , EDELWEISS experiment, IPNL, Particle Physics, ,   

    From IPNL: “First Results of the EDELWEISS III experiment” 

    ipnl-bloc

    Institut de Physique Nucleaire de Lyon

    13 May, 2016 [I just found these guys]
    Cazes Antoine

    1
    EDELWEISS bolometers before installation. No image credit

    The EDELWEISS experiment aims to detect WIMPs, a candidate for dark matter particles. It is located in the Modane Underground Laboratory. The experiment operates bolometers cooled to tens of Millikelvin where a WIMP might collide with a germanium nucleus and produce its recoil. This recoil is then measured by the resulting temperature rise (few microkelvin) and ionisation production (Germanium is a semiconductor material). This double measurment allow to identify nuclear recoils and thus eliminating much of the background due to gamma rays from natural radioactivity.

    For the third phase of the EDELWEISS experiment, the bolometers have been greatly improved and the cryostat was redesigned to reduce background noise and to accommodate a larger mass of detector. The experiment ran from July 2014 to April 2015. The data, equivalent to 582 kg.days were blindly analyzed and the background rejection was performed using a Boosted Decision Tree. This results in a lack of detection of WIMP and an improvement, by a factor varying between 12 to 41, compared to the previous limit EDELWEISS II: for a WIMP 5 GeV / c2, the collision cross sections WIMP -nucléon above 4.3×10-40 cm2 are excluded and those above 9.4×10-44 cm2 for WIMPs 20 GeV / c2.

    The EDELWEISS experiment is now working on a major R & D with the aim of lowering bolometers detection thresholds to explore collisions with low-mass WIMP (below 5 GeV / c2). This work is carried out in particular with the IOL cryostat installed IPNL.

    Science paper:
    Constraints on low-mass WIMPs from the EDELWEISS-III dark matter search

    See the full article here .

    ipnl-campus

     
  • richardmitnick 1:14 pm on November 25, 2016 Permalink | Reply
    Tags: , , , NA64 experiment hunts the mysterious dark photon, , Particle Physics   

    From CERN: “NA64 hunts the mysterious dark photon” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    25 Nov 2016
    Stefania Pandolfi
    Posted by Corinne Pralavorio

    1
    An overview of the NA64 experimental set-up at CERN. NA64 hunts down dark photons, hypothetic dark matter particles. (Image: Maximilien Brice/CERN)

    One of the biggest puzzles in physics is that eighty-five percent of the matter in our universe is “dark”: it does not interact with the photons of the conventional electromagnetic force and is therefore invisible to our eyes and telescopes. Although the composition and origin of dark matter are a mystery, we know it exists because astronomers observe its gravitational pull on ordinary visible matter such as stars and galaxies.

    Some theories suggest that, in addition to gravity, dark matter particles could interact with visible matter through a new force, which has so far escaped detection. Just as the electromagnetic force is carried by the photon, this dark force is thought to be transmitted by a particle called “dark” photon which is predicted to act as a mediator between visible and dark matter.

    “To use a metaphor, an otherwise impossible dialogue between two people not speaking the same language (visible and dark matter) can be enabled by a mediator (the dark photon), who understands one language and speaks the other one,” explains Sergei Gninenko, spokesperson for the NA64 collaboration.

    CERN’s NA64 experiment looks for signatures of this visible-dark interaction using a simple but powerful physics concept: the conservation of energy. A beam of electrons, whose initial energy is known very precisely, is aimed at a detector. Interactions between incoming electrons and atomic nuclei in the detector produce visible photons. The energy of these photons is measured and it should be equivalent to that of the electrons. However, if the dark photons exist, they will escape the detector and carry away a large fraction of the initial electron energy.

    Therefore, the signature of the dark photon is an event registered in the detector with a large amount of “missing energy” that cannot be attributed to a process involving only ordinary particles, thus providing a strong hint of the dark photon’s existence.

    If confirmed, the existence of the dark photon would represent a breakthrough in our understanding the longstanding dark matter mystery.


    View of the NA64 experiment set-up. (Video: Christoph Madsen/Noemi Caraban/CERN)

    See the full article here.

    Please help promote STEM in your local schools.

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    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 9:22 am on November 21, 2016 Permalink | Reply
    Tags: , , , , , Particle Physics,   

    From Symmetry- “Q and A: What more can we learn about the Higgs?” 

    Symmetry Mag

    Symmetry

    11/17/16
    Angela Anderson

    1
    Illustration by Sandbox Studio, Chicago with Ana Kova

    Four physicists discuss Higgs boson research since the discovery.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    More than two decades before the discovery of the Higgs boson, four theoretical physicists wrote a comprehensive handbook called The Higgs Hunter’s Guide. The authors—Sally Dawson of the Department of Energy’s Brookhaven National Laboratory; John F. Gunion from the University of California, Davis; Howard E. Haber from the University of California, Santa Cruz; and Gordon Kane from the University of Michigan—were recently recognized for “instrumental contributions to the theory of the properties, reactions and signatures of the Higgs boson” as recipients of the American Physical Society’s 2017 J.J. Sakurai Prize for Theoretical Physics.

    They are still investigating the particle that completed the Standard Model, and some are hunting different Higgs bosons that could take particle physics beyond that 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.

    Dawson, Gunion and Haber recently attended the Higgs Couplings 2016 workshop at SLAC National Accelerator Laboratory, where physicists gathered to talk about the present and future of Higgs research. Symmetry interviewed all four to find out what’s on the horizon.

    S: What is meant by “Higgs couplings”?
    JG: The Higgs is an unstable particle that lasts a very short time in the detector before it decays into pairs of things like top quarks, gluons, and photons. The rates and relative importance of these decays is determined by the couplings of the Higgs boson to these different particles. And that’s what the workshop is all about, trying to determine whether or not the couplings predicted in the Standard Model agree with the couplings that are measured experimentally.

    SD: Right, we can absolutely say how much of the time we expect the Higgs to decay to the known particles, so a comparison of our predictions with the experimental measurements tells us whether there’s any possible deviation from our Standard Model.

    JG: For us what would be really exciting is if we did see deviations. However, that probably requires more precision than we currently have experimentally.

    GK: But we don’t all agree on that, in the sense that I would prefer that it almost exactly agree with the Standard Model predictions because of a theory that I like that says it should. But most of the people in the world would prefer what John and Sally said.

    S.How many people are working in Higgs research now worldwide?

    GK: I did a search for “Higgs” in the title of scientific papers after 2011 on arXiv.org and came up with 5211 hits; there are several authors per paper, of course, and some have written multiple papers, so we can only estimate.

    SD: There are roughly 5000 people on each experiment, ATLAS and CMS, and some fraction of those work on Higgs research, but it’s really too hard to calculate. They all contribute in different ways. Let’s just say many thousands of experimentalists and theorists worldwide.
    What are Higgs researchers hoping to accomplish?

    HH: There are basically two different avenues. One is called the precision Higgs program designed to improve precision in the current data. The other direction addresses a really simple question: Is the Higgs boson a solo act or not? If additional Higgs-like particles exist, will they be discovered in future LHC experiments?

    SD: I think everybody would like to see more Higgs bosons. We don’t know if there are more, but everybody is hoping.

    JG: If you were Gordy [Kane] who only believes in one Higgs boson, you would be working to confirm with greater and greater precision that the Higgs boson you see has precisely the properties predicted in the Standard Model. This will take more and more luminosity and maybe some future colliders like a high luminosity LHC or an e+e- collider.

    HH: The precision Higgs program is a long-term effort because the high luminosity LHC is set to come online in the mid 2020s and is imagined to continue for another 10 years. There are a lot of people trying to predict what precision could you ultimately achieve in the various measurements of Higgs boson properties that will be made by the mid 2030s. Right now we have a set of measurements with statistical and systematic errors of about 20 percent. By the end of the high luminosity LHC, we anticipate that the size of the measurement errors can be reduced to around 10 percent and maybe in some cases to 5 percent.

    S. How has research on the topic changed since the Higgs discovery?

    SD: People no longer build theoretical models that don’t have a Higgs in them. You have to make sure that your model is consistent with what we know experimentally. You can’t just build a crazy model; it has to be a model with a Higgs with roughly the properties we’ve observed, and that is actually pretty restrictive.

    JG: Many theoretical models have either been eliminated or considerably constrained. For example, the supersymmetric models that are theoretically attractive kind of expect a Higgs boson of this mass, but only after pushing parameters to a bit of an extreme. There’s also an issue called naturalness: In the Standard Model alone there is no reason why the Higgs boson should have such a light mass as we see, whereas in some of these theories it is natural to see the Higgs boson at this mass. So that’s a very important topic of research—looking for those models that are in a certain sense naturally predicting what we see and finding additional experimental signals associated with such models.

    GK: For example, the supersymmetric theories predict that there will be five Higgs bosons with different masses. The extent to which the electroweak symmetry is broken by each of the five depends on their couplings, but there should be five discovered eventually if the others exist.

    HH: There’s also a slightly different attitude to the research today. Before the Higgs boson was discovered it was known that the Standard Model was theoretically inconsistent without the Higgs boson. It had to be there in some form. It wasn’t going to be that we ran the LHC and saw nothing—no Higgs boson and nothing else. This is called a no-lose theorem. Now, having discovered the Higgs boson, you cannot guarantee that additional new phenomenon exists that must be discovered at the LHC. In other words, the Standard Model itself, with the Higgs boson, is a theoretically consistent theory. Nevertheless, not all fundamental phenomena can be explained by Standard Model physics (such as neutrino masses, dark matter and the gravitational force), so we know that new phenomena beyond the Standard Model must be present at some very high-energy scale. However, there is no longer a no-lose theorem that states that this new phenomena must appear at the energy scale that is probed at the LHC.

    S. How have the new capabilities of the LHC changed the game?

    SD: We have way more Higgs bosons; that’s really how it’s changed. Since the energy is higher we can potentially make heavier new particles.

    GK: There were about a million Higgs bosons produced in the first run of the LHC, and there will be more than twice that in the second run, but they only can find a small fraction of those in the detector because of background noise and some other things. It’s very hard. It takes clever experimenters. To find a couple of hundred Higgs you need to produce a million.

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

    SD: Most of the time the Higgs decays into something we can’t see in our detector. But as the measurements get better and better, experimentalists who have been extracting the couplings are quantifying more properties of the Higgs decays. So instead of just counting how many Higgs bosons decay to two Z bosons, they will look at where the two Z bosons are in the detector or the energy of the Z bosons.

    S. Are there milestones you are looking forward to?

    GK: Confirming the Standard Model Higgs with even more precision. The decay the Higgs boson was discovered in—two photons—could happen in any other kind of particle. But the decay to W boson pairs is the one that you need for it to break the electroweak symmetry [a symmetry between the masses of the particles associated with the electromagnetic and weak forces], which is what it should do according to the Standard Model.

    SD: So, one of the things we will see a lot of in the next year or two is better measurements of the Higgs decay into the bottom quarks. Within a few years, we should learn whether or not there are more Higgs bosons. Measuring the couplings to the desired precision will take 20 years or more.

    JG: There’s another thing people are thinking about, which is how the Higgs can be connected to the important topic of dark matter. We are working on models that establish such a connection, but most of these models, of course, have extra Higgs bosons. It’s even possible that one of those extra Higgs bosons might be invisible dark matter. So the question is whether the Higgs we can see tells us something about dark matter Higgs bosons or other dark matter particles, such as the invisible particles that are present in supersymmetry.

    S. Are there other things still to learn?

    JG: There are many possible connections between Higgs bosons, in a generic sense and the history of the universe. For example, it could be that a Higgs-like particle called the inflaton is responsible for the expansion of the universe. As a second example, generalized Higgs boson models could explain the preponderance of matter over antimatter in the current universe.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 11:41 am on November 18, 2016 Permalink | Reply
    Tags: , , Particle Physics, ,   

    From SURF: “Construction of World’s Most Sensitive Dark Matter Detector Moves Forward” 

    SURF logo
    Sanford Underground levels

    Sanford Underground Research facility

    September 26, 2016
    Constance Walter

    LUX-ZEPLIN (LZ), a next-generation dark matter detector that will be at least 100 times more sensitive than its predecessor, has cleared another approval milestone and is on schedule to begin its deep-underground hunt for theoretical particles known as WIMPs, or weakly interacting massive particles, in 2020.

    Lux Zeplin project at SURF
    Lux Zeplin project at SURF

    WIMPs are among the top prospects for explaining dark matter, the unseen stuff that we have observed only through gravitational effects.

    Last month, LZ received an important U.S. Department of Energy approval (known as Critical Decision 2 and 3b) for the project’s overall scope, cost and schedule. The latest approval step sets in motion the build-out of major components and the preparation of its mile-deep lair at the Sanford Underground Research Facility (SURF) in Lead, S.D.

    The experiment is designed to tease out dark matter signals from within a chamber filled with 10 metric tons of purified liquid xenon, one of the rarest elements on Earth. The project is supported by a collaboration of more than 30 institutions and about 200 scientists worldwide.

    “The nature of the dark matter, which comprises 85 percent of all matter in the universe, is one of the most perplexing mysteries in all of contemporary science,” said Harry Nelson, LZ spokesperson and a physics professor at University of California, Santa Barbara. “Just as science has elucidated the nature of familiar matter—from the periodic table of elements to subatomic particles, including the recently discovered Higgs boson—the LZ project will lead science in testing one of the most attractive hypotheses for the nature of the dark matter.”

    LZ is named for the merger of two dark matter detection experiments: the Large Underground Xenon experiment (LUX) and the U.K.-based ZonEd Proportional scintillation in Liquid Nobel gases experiment (ZEPLIN). LUX, a smaller liquid xenon-based underground experiment at SURF will be dismantled to make way for the new project.

    “Liquid Xenon has turned out to be a nearly magical substance for WIMP detection, as demonstrated by the sensitivities achieved by ZEPLIN and LUX,“ said Professor Henrique Araujo from Imperial College London, who leads the project in the U.K.

    The SURF site shields the experiment from many particle types that are constantly showering down on the Earth’s surface and would obscure the signals LZ is seeking.

    “Nobody looking for dark matter interactions with matter has so far convincingly seen anything, anywhere, which makes LZ more important than ever,” said Murdock “Gil” Gilchriese, LZ project director and Berkeley Lab physicist.

    Dan McKinsey, a Lawrence Berkeley National Laboratory (Berkeley Lab) faculty senior scientist and UC Berkeley Physics professor who is a part of the LZ collaboration, said, “A major reason for LZ is surprises: We’re really pushing way into the low-energy, low-background parameter space where no one has ever looked, and this is where surprises could await. That’s where new things get discovered. While we are looking for dark matter, we may see something else that has a rare interaction with matter at low energies.”

    Some previous and planned experiments that also use liquid xenon as the medium for dark-matter detection are helping to set the stage for LZ.

    Experiments seeking traces of dark matter have grown increasingly sensitive in a short time, Gilchriese said, noting, “It’s really like Moore’s law,” an observation about regular, exponential growth in computing power through the increasing concentration of transistors on a computer chip over time. “The technologies used in liquid xenon detectors have been demonstrated around the world.”

    The entire supply of xenon for the project is already under contract, Gilchriese said, and the state of South Dakota aided in the purchase of this supply. Xenon gas, which is costly to produce, is used in lighting, medical imaging and anesthesia, space-vehicle propulsion systems, and the electronics industry.

    Before the xenon is delivered in gas form in tanks to South Dakota, it will be purified at SLAC National Accelerator Laboratory.

    “Having focused on design and prototyping for some time now, it’s very exciting to be moving forward toward building the LZ detector and the production-scale purification systems that will process its xenon,” said Dan Akerib, who co-leads SLAC’s LZ team. “The goal is to limit contamination from another element, krypton, to just one-tenth of a part per trillion.”

    Liquid xenon was selected because it can be ultra-purified, including the removal of most traces of radioactivity that could interfere with particle signals, and because it produces light and electrical pulses when it interacts with particles.

    Engineers at Fermi National Accelerator Laboratory and the University of Wisconsin’s Physical Sciences Laboratory are working together to make sure that none of that expensive xenon is lost should there be a power outage or extended down time.

    “The xenon in LZ is precious both scientifically and financially, so it’s very important that we have the same amount of xenon at the end of the experiment as at the beginning,” said Hugh Lippincott of Fermilab, the current physics coordinator of the collaboration. “We’re excited to be part of this next generation of direct dark matter experiments.”

    LZ is designed so that a dark matter particle would produce a prompt flash of light followed by a second flash of light when the electrons produced in the liquid xenon chamber drift to its top. The light pulses, picked up by a series of about 500 light-amplifying tubes lining the massive tank, will carry the telltale fingerprint of the particles that created them.

    The tubes are currently being manufactured by a company in Japan and will be tested by collaboration members. Progress is also continuing on the construction of ultrapure titanium sheets in Italy that will be formed, fitted and welded together to create a double-walled vessel that will hold the liquid xenon.

    In recent weeks, researchers used LUX, which will soon be dismantled, as a test bed for prototype LZ electronics. They tested new approaches in monitoring and measuring particle signals, which will help them in fine-tuning the LZ detector.

    “We have learned a ton of stuff from LUX,” McKinsey said. “We are mixing in some different forms of elements that we can remove really well or that decay to stable isotopes—to measure all of the responses of the liquid xenon detector. We are making sure our errors are small when we actually do the LZ experiment.”

    Other work is focused on precisely measuring the slightest contribution to background noise in the detector posed by all of the components that will surround the liquid xenon, to help predict what the detector will see once it’s turned on. A high-voltage system is being tested at Berkeley Lab that will generate an electric field within the detector to guide the flow of electrons produced in particle interactions to the top of the liquid xenon chamber.

    “At SLAC, we’ve set up an entire platform where the LZ collaboration is testing detector prototypes and is performing all kinds of system tests,” said Tom Shutt, co-leader of the national lab’s LZ group and LUX co-founder.

    In the next year there will be lot of work at SURF to disassemble LUX and prepare the underground site for LZ assembly and installation. Much of the onsite assembly for LZ will take place in 2018-2019 at SURF.

    Kevin Lesko, a senior physicist at Berkeley Lab and head of Berkeley Lab’s SURF operations office, said that LZ will benefit from previous work at the SURF site to prepare for new and larger experiments. “Back in 2009, we sized the water tank and other infrastructure to support next-generation experiments,” he said.

    Strong scientific teams from the U.K., Portugal, Russia, and South Korea are making crucial physical and intellectual contributions to the LZ project. For more information about the LZ collaboration, visit: http://lz.lbl.gov/collaboration/.

    LZ is supported by the U.S. Department of Energy’s Office of High Energy Physics, the U.K. Science & Technology Facilities Council, the Portuguese Foundation for Science and Technology, and the South Dakota Science and Technology Authority (SDSTA), which developed the Sanford Underground Research Facility (SURF). SURF is operated by the SDSTA under a contract with the Lawrence Berkeley National Laboratory for the Department of Energy’s Office of High Energy Physics.

    See the full article here .

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    About us.
    The Sanford Underground Research Facility in Lead, South Dakota, advances our understanding of the universe by providing laboratory space deep underground, where sensitive physics experiments can be shielded from cosmic radiation. Researchers at the Sanford Lab explore some of the most challenging questions facing 21st century physics, such as the origin of matter, the nature of dark matter and the properties of neutrinos. The facility also hosts experiments in other disciplines—including geology, biology and engineering.

    The Sanford Lab is located at the former Homestake gold mine, which was a physics landmark long before being converted into a dedicated science facility. Nuclear chemist Ray Davis earned a share of the Nobel Prize for Physics in 2002 for a solar neutrino experiment he installed 4,850 feet underground in the mine.

    Homestake closed in 2003, but the company donated the property to South Dakota in 2006 for use as an underground laboratory. That same year, philanthropist T. Denny Sanford donated $70 million to the project. The South Dakota Legislature also created the South Dakota Science and Technology Authority to operate the lab. The state Legislature has committed more than $40 million in state funds to the project, and South Dakota also obtained a $10 million Community Development Block Grant to help rehabilitate the facility.

    In 2007, after the National Science Foundation named Homestake as the preferred site for a proposed national Deep Underground Science and Engineering Laboratory (DUSEL), the South Dakota Science and Technology Authority (SDSTA) began reopening the former gold mine.

    In December 2010, the National Science Board decided not to fund further design of DUSEL. However, in 2011 the Department of Energy, through the Lawrence Berkeley National Laboratory, agreed to support ongoing science operations at Sanford Lab, while investigating how to use the underground research facility for other longer-term experiments. The SDSTA, which owns Sanford Lab, continues to operate the facility under that agreement with Berkeley Lab.

    The first two major physics experiments at the Sanford Lab are 4,850 feet underground in an area called the Davis Campus, named for the late Ray Davis. The Large Underground Xenon (LUX) experiment is housed in the same cavern excavated for Ray Davis’s experiment in the 1960s.
    LUX/Dark matter experiment at SURFLUX/Dark matter experiment at SURF

    In October 2013, after an initial run of 80 days, LUX was determined to be the most sensitive detector yet to search for dark matter—a mysterious, yet-to-be-detected substance thought to be the most prevalent matter in the universe. The Majorana Demonstrator experiment, also on the 4850 Level, is searching for a rare phenomenon called “neutrinoless double-beta decay” that could reveal whether subatomic particles called neutrinos can be their own antiparticle. Detection of neutrinoless double-beta decay could help determine why matter prevailed over antimatter. The Majorana Demonstrator experiment is adjacent to the original Davis cavern.

    Another major experiment, the Long Baseline Neutrino Experiment (LBNE)—a collaboration with Fermi National Accelerator Laboratory (Fermilab) and Sanford Lab, is in the preliminary design stages. The project got a major boost last year when Congress approved and the president signed an Omnibus Appropriations bill that will fund LBNE operations through FY 2014. Called the “next frontier of particle physics,” LBNE will follow neutrinos as they travel 800 miles through the earth, from FermiLab in Batavia, Ill., to Sanford Lab.

    Fermilab LBNE
    LBNE

     
  • richardmitnick 5:09 pm on November 14, 2016 Permalink | Reply
    Tags: , , , , Particle Physics   

    From Alice at CERN: “Proton-lead collision at 5.02 TeV as seen by ALICE” 

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    ALICE-EVENTDISPLAY-2016-011-1

    One of the first proton-lead events at 5.02 TeV as seen by ALICE in November 2016. The event comes from fill 5506 with 189 colliding bunches at an interaction rate of 17 kHz.

    Date: 11-11-2016

    See the full article here .

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  • richardmitnick 8:29 am on November 8, 2016 Permalink | Reply
    Tags: , CERN Linac 4, , , Particle Physics   

    From CERN: “Linac 4 reached its energy goal” 

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    Linac 4 during its installation in 2015. This photo was taken as part of the 2015 Photowalk competition (Image: Federica Piccinni/CERN)

    7 Nov 2016
    Corinne Pralavorio

    CERN’s new linear accelerator (Linac 4) has now accelerated a beam up to its design energy, 160 MeV. This important milestone of the accelerator’s commissioning phase took place on 25 October.

    Linac 4 is scheduled to become the source of proton beams for the CERN accelerator complex, including the Large Hadron Collider (LHC) after the long shutdown in 2019-2020. It will replace the existing Linac 2 as the first link in the accelerator chain, which is currently accelerating protons at 50 MeV. The new 30-metre-long accelerator will accelerate hydrogen ions – protons surrounded by two electrons – at 160 MeV, before sending them to the Proton Synchrotron Booster. Here, the ions are stripped of their two electrons to leave only the protons that will be further accelerated before finishing their race in the LHC.

    Linac 4 comprises four types of accelerating structures to bring particles in several stages to higher and higher energies. These accelerating structures have been commissioned one by one: in November 2013, the first hydrogen ion beam was accelerated to the energy of 3 MeV and two years after, the Linac 4 accelerator has reached an energy of 50 MeV – the energy Linac 2 runs at. Then, on the 1 July 2016, it crossed the 100 MeV threshold.

    See the full article here.

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  • richardmitnick 4:34 pm on November 3, 2016 Permalink | Reply
    Tags: , ASAUSA, , , , Particle Physics   

    From CERN: “CERN experiment improves precision of antiproton mass measurement with new innovative cooling technique” 

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    03 Nov 2016
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    The ASACUSA experiment (Image: CERN)
    Electrostatic protocol treatment lens. The purpose of this device is to transport Antiprotons from the new ELENA storage beam to all AD experiments. The electrostatic device was successfully tested in ASACUSA two weeks ago.

    In a paper published today in the journal Science, the ASACUSA experiment at CERN1 reported new precision measurement of the mass of the antiproton relative to that of the electron. This result is based on spectroscopic measurements with about 2 billion antiprotonic helium atoms cooled to extremely cold temperatures of 1.5 to 1.7 degrees above absolute zero. In antiprotonic helium atoms an antiproton takes the place of one of the electrons that would normally be orbiting the nucleus. Such measurements provide a unique tool for comparing with high precision the mass of an antimatter particle with its matter counterpart. The two should be strictly identical.

    “A pretty large number of atoms containing antiprotons were cooled below minus 271 degrees Celsius. It’s kind of surprising that a ‘half-antimatter’ atom can be made so cold by simply placing it in a refrigerated gas of normal helium,” said Masaki Hori, Group Leader of the ASACUSA collaboration.

    Matter and antimatter particles are always produced as a pair in particle collisions. Particles and antiparticles have the same mass and opposite electric charge. The positively charged positron, for example, is an anti-electron, the antiparticle of the negatively charged electron. Positrons have been observed since the 1930s, both in natural collisions from cosmic rays and in particle accelerators. They are used today in hospital in PET scanners. However, studying antimatter particles with high-precision remains a challenge because when matter and antimatter come into contact, they annihilate – disappearing in a flash of energy.

    CERN’s Antiproton Decelerator is a unique facility delivering low-energy antiproton beams to experiments for antimatter studies. In order to make measurements with these antiprotons, several experiments trap them for long periods using magnetic devices. ASACUSA’s approach is different as the experiment is able to create very special hybrid atoms made of a mix of matter and antimatter: these are the antiprotonic helium atoms composed of an antiproton and an electron orbiting a helium nucleus. They are made by mixing antiprotons with helium gas. In this mixture, about 3% of the antiprotons replace one of the two electrons of the helium atom. In antiprotonic helium, the antiproton is in orbit around the helium nucleus, and protected by the electron cloud that surrounds the whole atom, making antiprotonic helium stable enough for precision measurements.

    The measurement of the antiproton’s mass is done by spectroscopy, by shining a laser beam onto the antiprotonic helium. Tuning the laser to the right frequency causes the antiprotons to make a quantum jump within the atoms. From this frequency the antiproton mass relative to the electron mass can be calculated. This method has been successfully used before by the ASACUSA collaboration to measure with high accuracy the antiproton’s mass. However, the microscopic motion of the antiprotonic helium atoms introduced a significant source of uncertainty in previous measurements.

    The major new achievement of the collaboration, as reported in Science, is that ASACUSA has now managed to cool down the antiprotonic helium atoms to temperatures close to absolute zero by suspending them in a very cold helium buffer-gas. In this way, the microscopic motion of the atoms is reduced, enhancing the precision of the frequency measurement. The measurement of the transition frequency has been improved by a factor of 1.4 to 10 compared with previous experiments. Experiments were conducted from 2010 to 2014, with about 2 billion atoms, corresponding to roughly 17 femtograms of antiprotonic helium.

    According to standard theories, protons and antiprotons are expected to have exactly the same mass. To date, no difference has been found between their masses, but pushing the precision limits of this comparison is a very important test of key theoretical principles such as the CPT symmetry. CPT is a consequence of basic symmetries of space-time, such as its isotropy in all directions. The observation of even a minute breaking of CPT would call for a review of our assumptions about the nature and properties of space-time.

    The ASACUSA collaboration is confident that it will be able to further improve the precision of antiproton’s mass by using two laser beams. In the near future, the start of the ELENA facility at CERN will also allow the precision of such measurements to be improved.

    See the full article here.

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