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  • richardmitnick 4:25 pm on December 6, 2016 Permalink | Reply
    Tags: 2016: an exceptional year for the LHC, Accelerator Science, , , , , ,   

    From CERN: “2016: an exceptional year for the LHC” 

    Cern New Bloc

    Cern New Particle Event

    CERN New Masthead

    CERN

    6 Dec 2016
    Corinne Pralavorio

    1
    This proton-lead ion collision in the ATLAS detector produced a top quark – the heaviest quark – and its antiquark (Image: ATLAS)

    It’s the particles’ last lap of the ring. On 5 December 2016, protons and lead ions circulated in the Large Hadron Collider (LHC) for the last time. At exactly 6.02am, the experiments recorded their last collisions (also known as ‘events’).

    When the machines are turned off, the LHC operators take stock, and the resulting figures are astonishing.

    The number of collisions recorded by ATLAS and CMS during the proton run from April to the end of October was 60% higher than anticipated. Overall, all of the LHC experiments observed more than 6.5 million billion (6.5 x 1015) collisions, at an energy of 13 TeV. That equates to more data than had been collected in the previous three runs combined.

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    One of the first proton-lead ion collisions at 8.16 TeV recorded by the ALICE experiment. (Image: ALICE/CERN)

    In technical terms, the integrated luminosity received by ATLAS and CMS reached 40 inverse femtobarns (fb−1), compared with the 25fb−1 originally planned. Luminosity, which measures the number of potential collisions in a given time, is a crucial indicator of an accelerator’s performance.

    “One of the key factors contributing to this success was the remarkable availability of the LHC and its injectors,” explains Mike Lamont, who leads the team that operates the accelerators. The LHC’s overall availability in 2016 was just shy of 50%, which means the accelerator was in ‘collision mode’ 50% of the time: a very impressive achievement for the operators. “It’s the result of an ongoing programme of work over the last few years to consolidate and upgrade the machines and procedures,” Lamont continues.

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    An event recorded by the CMS experiment during the LHC’s proton-lead ion run for which no fewer than 449 particles tracks were reconstructed. (Image: CMS/CERN)

    For the last four weeks, the machine has turned to a different type of collision, where lead ions have been colliding with protons. “This is a new and complex operating mode, but the excellent functioning of the accelerators and the competence of the teams involved has allowed us to surpass our performance expectations,” says John Jowett, who is in charge of heavy-ion runs.

    With the machine running at an energy of 8.16 TeV, a record for this assymetric type of collision, the experiments have recorded more than 380 billion collisions. The machine achieved a peak luminosity over seven times higher than initially expected, as well as exceptional beam lifetimes. The performance is even more remarkable considering that colliding protons with lead ions, which have a mass 206 times greater and a charge 82 times higher, requires numerous painstaking adjustments to the machine.

    The physicists are now analysing the enormous amounts of data that have been collected, in preparation for presenting their results at the winter conferences.

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    A proton-lead ion collision recorded by the LHCb experiment in the last few days of the LHC’s 2016 run. (Image: LHCb)

    Meanwhile, CERN’s accelerators will take a long break, called the Extended Year End Technical Stop (EYETS) until the end of March 2017. But, while the accelerators might be on holiday, the technical teams certainly aren’t. The winter stop is an opportunity to carry out maintenance on these extremely complex machines, which are made up of thousands of components. The annual stop for the LHC is being extended by two months in 2017 to allow more major renovation work on the accelerator complex and its 35 kilometres of machines to take place. Particles will return to the LHC in spring 2017.

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    The integrated luminosity of the LHC with proton-proton collisions in 2016 compared to previous years. Luminosity is a measure of a collider’s efficiency and is proportional to the number of collisions. The integrated luminosity achieved by the LHC in 2016 far surpassed expectations and is double that achieved at a lower energy in 2012. (Image : CERN)

    See the full article here.

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    Meet CERN in a variety of places:

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

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

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    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.”

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    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.

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    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.

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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
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    Quantum Diaries

     
  • richardmitnick 9:22 am on November 21, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , , ,   

    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 5:09 pm on November 14, 2016 Permalink | Reply
    Tags: Accelerator Science, , , ,   

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

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    1
    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 3:23 pm on November 12, 2016 Permalink | Reply
    Tags: Accelerator Science, Accelerator Science: Circular vs. Linear, ,   

    From Don Lincoln at FNAL: “Accelerator Science: Circular vs. Linear “ 

    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.
    Nov 10, 2016

    FNAL Don Lincoln
    Don Lincoln

    Particle accelerator are scientific instruments that allow scientists to collide particles together at incredible energies to study the secrets of the universe. However, there are many manners in which particle accelerators can be constructed. In this video, Fermilab’s Dr. Don Lincoln explains the pros and cons of circular and linear accelerators.

    See the full article here .

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    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 8:29 am on November 8, 2016 Permalink | Reply
    Tags: Accelerator Science, CERN Linac 4, , ,   

    From CERN: “Linac 4 reached its energy goal” 

    Cern New Bloc

    Cern New Particle Event

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    CERN

    1
    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 10:59 am on November 4, 2016 Permalink | Reply
    Tags: Accelerator Science, , , , The buzz from CMS   

    From FNAL: “The buzz from CMS” 

    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 4, 2016
    Vivan O’Dell

    CERN/CMS Detector
    CERN/CMS Detector

    The CMS experiment at CERN’s Large Hadron Collider is buzzing with activity.

    CERN/LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC st CERN

    The first year of Run 2 is ending, and as we near the end of 2016, we have our work cut out for us.

    CMS is upgrading its inner tracking detector over the winter during a 21-week temporary halt of beams. We’re preparing for more upgrades during the second LHC long shutdown in 2018-19. We’re also finalizing designs for a major upgrade, targeting the 10-year running period from 2026-3035. CMS is like three experiments at once: one collecting and analyzing data, one in the final stages of building and installing, and one in the early design phase.

    The major upgrade, the High-Luminosity LHC upgrades, targets the detectors as well as the accelerator, and Fermilab has major responsibilities in both of these areas. Fermilab is the host lab for U.S. contributions to CMS and is home to the CMS HL-LHC upgrade project office. We are also a major player in the upgrades of tracking, calorimetry and trigger. These upgrades will allow CMS to run efficiently in a high-collision-rate and high-radiation environment.

    Last year, CERN officially approved the CMS and ATLAS detector upgrades to move from proposal phase to detailed technical designs, which is similar to a project “baselining” phase. This was followed in April with both NSF and DOE officially recognizing the U.S. contributions to the HL-LHC CMS upgrades: We received CD-0 approval for the detector upgrades from DOE and the official approval to move into the preliminary-design phase from NSF. The U.S. contributions to the accelerator also achieved CD-0 in April.

    The next year will be a busy year for the CMS HL-LHC upgrades: In the United States we are planning for DOE CD-1 in the fall and the NSF Preliminary Design Review at the end of the year. Internationally, CMS is working on delivering four detailed technical design reports, which cover all aspects of the upgrades, their costs, and the planned international contributions to build and maintain them. Luckily the sun never sets on the CMS collaboration, and the CMS Center at Fermilab offers unlimited espresso.

    Both upgrades, which will be installed over the next couple of years, will enable CMS to collect nearly 100 times more data at its current center-of-mass collision energy, which is roughly 14 TeV. That boost in data volume increases the potential for making significant discoveries of new phenomena to complete our understanding of particle physics and allows more precise measurements of Higgs boson properties and other tests of Standard Model processes.

    Vivian O’Dell is the U.S. CMS Phase II upgrade project manager.

    See the full article here .

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    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 4:34 pm on November 3, 2016 Permalink | Reply
    Tags: Accelerator Science, ASAUSA, , , ,   

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

    Cern New Bloc

    Cern New Particle Event

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    CERN

    03 Nov 2016
    No writer credit found

    1
    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.

    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 9:59 am on November 1, 2016 Permalink | Reply
    Tags: Accelerator Science, , , ,   

    From FNAL: “What happens at the Test Beam Facility?” 

    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.

    October 26, 2016
    No writer credit found

    1

    Many staff know the Fermilab Test Beam Facility as that building with the roof made of arched half pipes, but how many of us know what goes on under that roof?

    Physicist Mandy Rominsky has recently been leading tours of the facility, known as FTBF, for Fermilab employees. Fermilab Art Gallery curator Georgia Schwender snapped this photo of Rominsky, the facility’s manager, whose enthusiasm for the work was evident, Schwender said.

    Particle physicists from all over the world come to FTBF to conduct tests on their particle detectors, signing up for one or two weeks to use the facility, just like one might rent a timeshare.

    The users bring or ship their detectors to FTBF prior to or during their time slot. They install their detectors in the path one of the facility’s two beamlines, run beam through it 24/7, and measure the detectors’ responses to the beam. At the end of the test period, scientists are better able to characterize their detectors.

    FTBF can supply all kinds of particle beams, anywhere from 200 million to 120 billion electronvolts of energy. It can provide a proton beam and can produce beams of secondary particles, such as muons, pions, electrons and kaons.

    Four people run the facility: Rominsky, Physicist JJ Schmidt, Instrument Specialist Ewa Skup and Technician Todd Nebel. The quartet gets tremendous help from throughout the lab, and especially the Particle Physics and Accelerator divisions.

    Thanks to the FTBF crew for your excellent work!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 11:05 am on October 25, 2016 Permalink | Reply
    Tags: Accelerator Science, , , No, , , The LHC Hasn't Shown That We Live In A Multiverse   

    From Ethan Siegel: “No, The LHC Hasn’t Shown That We Live In A Multiverse” 

    Oct 25, 2016
    Ethan Siegel

    Post written by
    Sabine Hossenfelder
    Sabine is a theoretical physicist specialized in quantum gravity and high energy physics. She also freelance writes about science.

    1
    The multiverse idea states that there are infinite numbers of Universes like our own, and infinite ones with differences. Image credit: flickr user Lee Davy, via https://www.flickr.com/photos/chingster23/11937781733. (CC BY 2.0)

    “I read the LHC people have shown we live in a multiverse!” my mom says when she opens the door. It wasn’t really the welcome I expected. Recently retired, she now regularly attends lecture series at the university. Mostly, she finds them annoyingly dumbed down.

    Unlike my brother, The Engineer Who Will Fix It, I and my PhD in theoretical physics have never been of much use. But suddenly, I’m the go-to person for “black holes” and “gravitational waves” and “have you read that dark matter causes cancer?”

    I can’t blame my mom for the multiverse nonsense – it has become widespread. If you believe Scientific American then “New Physics Complications Lend Support to Multiverse Hypothesis.” From Vox you can learn that “If the LHC can’t find answers to questions like ‘why is the Higgs so light?’ scientists might grow to accept a more out-of-the-box idea: the multiverse.” And according to Business Insider, “If supersymmetry is wrong, [it would] lend more credence to other theories, like the idea that we live in a multiverse.”

    2
    The Standard Model of particle physics. There must be more to nature than this. Image credit: Wikimedia Commons user Latham Boyle, under c.c.a.-by-s.a.-4.0.

    The multiverse – a conjectured endless collection of universes – was once the realm of science fiction, but now it’s science. Physicists have conjectured that the laws of nature in each of the universes would be slightly different, and the possibilities are limitless. In some universes electrons would be much heavier than they are in ours, or atoms would decay faster, or gravity would be much stronger. Really anything could happen.

    Not only would anything that could happen actually happen in some universe within the multiverse, but anything that can happen would happen infinitely many times. Therefore, the multiverse also contains infinitely many universes that are almost exactly like our own, including our planet, and me, and you. But in some of these other universes, a dark matter particle gave you cancer ten years ago. Don’t worry that you might accidentally get condolences for your other self, though. The universes aren’t causally connected and information exchange not possible.

    3
    The observable Universe, 46 billion light years in radius, within the larger, unobservable Universe. Image credit: Wikimedia Commons users Frédéric MICHEL and Azcolvin429, annotated by E. Siegel.

    Many of the other universes, however, would not contain living beings, because not every combination of natural possibilities for the laws of physics allows for sufficiently complex structures to form. A universe that expands too fast, for example, or that recollapses too quickly, would contain merely a well-mixed soup of elementary particles which, for all we know, wouldn’t write essays.

    So some physicists think that their models for the early universe demonstrate there wouldn’t be only one universe but infinitely many. Ok then, you might say, weird enough, but what does this have to do with the LHC?

    4
    The particle tracks emanating from a high energy collision at the LHC in 2014. Image credit: Wikimedia Commons user Pcharito, under a c.c.a.-by-s.a.-3.0 license.

    The connection to the LHC comes about because theoretical physicists are not satisfied with the currently best laws of nature they have: the standard model of particle physics plus general relativity.

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

    They want to do better. The standard model contains many parameters for which they have no deeper explanation, and they are hoping that there exists an underlying – more fundamental – theory from which the parameters can be calculated.

    A parameter that irks theoretical physicists particularly is the mass of the recently discovered Higgs-boson.

    CERN CMS Higgs Event
    CERN CMS Higgs Event

    CERN ATLAS Higgs Event
    CERN ATLAS Higgs Event

    It comes out to be about 125 GeV. That value is somewhat more than 100 times the mass of a proton and, on its own, sounds pretty unremarkable. But the Higgs-boson is a special particle in that it’s the only known (fundamental) scalar, which means it has spin zero. As a consequence of this, the mass of the Higgs-boson acquires correction terms from quantum fluctuations, and these correction terms are very large – larger than the observed value by almost 15 orders of magnitude.

    5
    The discovery of the Higgs Boson in the di-photon (γγ) channel at CMS. Image credit: CERN / CMS Collaboration.

    These large quantum-corrections to the Higgs-boson’s mass can be removed by subtracting a new term which is almost (but not exactly) equally large, so that the difference leaves behind the, comparably tiny, observed mass. This is possible because the observed mass is a parameter which has to be determined experimentally anyway. However, such a delicate cancellation requires finetuning: You need two constants that are equal for the first 15 digits and then differ in the 16th. If you’d pick two random numbers this would be extremely unlikely. It seems hand-selected and hence in need of explanation.

    For this reason, physicists say that the small mass of the Higgs-boson is “not natural.”

    The Higgs mass is the only parameter in the standard model which is not natural. Physicists understood this long before the Higgs itself was discovered, and for this reason many of them believed that the LHC would also find evidence for new physics besides the Higgs. The new physics, so they thought, was necessary to explain the smallness of the Higgs mass and thereby make it natural.

    6
    The Standard Model particles and their supersymmetric counterparts. Exactly 50% of these particles have been discovered, and 50% have never showed a trace that they exist. Image credit: Claire David, of http://davidc.web.cern.ch/davidc/index.php?id=research.

    The best studied hypothesis to make the Higgs-mass natural is supersymmetry. In supersymmetric theories, every known particle comes with a partner-particle. One consequence of this doubling is that the troublesome quantum-contributions to the Higgs-mass cancel. The new symmetry enforces a cancellation, since there now must be equally large contributions to these quantum corrections with either sign: one from the normal particles and one from the supersymmetric ones.

    At least, that would be so if supersymmetry were an exact symmetry of nature. We already know, however, that this can’t be the case, because then we should have seen superpartners of the standard model particles long ago. So, theoretical physicists concluded, supersymmetry must be broken, and it’s only restored above some energy scale, the “SUSY breaking scale.” The SUSY breaking scale should be in the range of the LHC, because this would make the Higgs-mass natural. If the SUSY breaking scale were much higher than that, the need to delicately cancel quantum contributions by fine-tuning would come back.

    The way things went, however, the LHC found the Higgs but no evidence for anything new besides that. No supersymmetry, no extra-dimensions, no black holes, no fourth generation, nothing. This means that the Higgs-mass just sits there, boldly unnatural.

    7
    A representation of the different parallel “worlds” that might exist in other pockets of the multiverse. Image credit: public domain, retrieved from https://pixabay.com/en/globe-earth-country-continents-73397/.

    That’s where the multiverse comes in.

    Since theoretical physicists haven’t found an explanation for the smallness of the Higgs-mass, they now try to accept that there simply may be no explanation. And if there is no explanation, so the argument goes, then no single value is special, and this must mean that all possible mass values have the same right to existence. In this case there should be a universe for any possible value of the Higgs mass. And for any possible value of every other particle’s mass. In other words, there should be a multiverse which contains universes for all possible combinations of parameters.

    In the multiverse, the value of the Higgs would be selected only to the extent that it needs to enable the development of life like ours – the so-called “anthropic principle.” But since the development of life isn’t well understood itself – and in any case certainly not the domain of physicists – this is presently a fairly vague requirement.

    8
    The evolution of our Universe as we know it to be requires the cosmological parameters to take on a particular set of values; too different and this Universe would never give rise to lifeforms like us. Image credit: NASA / WMAP science team.

    So, in a nutshell, the argument is that since theoretical physicists can’t explain the mass of the Higgs, any parameter can take on any possible value and we live in a multiverse.

    It’s an interesting argument but it’s logically inconsistent. It relies on an expectation about what we mean by a “random number” or its probability distribution, respectively. There are infinitely many such distributions. The requirement that the numbers in the standard model should obey a certain distribution is merely a hypothesis that turned out to be incompatible with observation. That, really, is all we can conclude from the data: physicists had a hypothesis for what is “natural.” It turned out to be wrong.

    This doesn’t mean there is no multiverse. There might or might not be one. It just means the LHC results don’t tell us anything about it.

    I spent an hour explaining theoretical high energy physics to my mom and assured her the LHC hasn’t shown we live in a multiverse. She now understands how the Higgs gets its mass, but she doesn’t understand why newspapers write multiverse headlines. I can’t help her with that.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    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

     
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