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  • richardmitnick 2:41 pm on December 16, 2014 Permalink | Reply
    Tags: , , Boston University, , , Particle Accelerators,   

    From BU: “Trigger Happy” 

    Boston University Bloc

    Boston University

    December 1, 2014
    Barbara Moran

    Physicist Tulika Bose talks about smashing protons to find new physics

    tb
    Tulika Bose, trigger coordinator for the Compact Muon Solenoid experiment at the Large Hadron Collider in Switzerland. “Trigger meetings are dramatic places,” she says. Photo by Jackie Ricciardi

    Tulika Bose is a science detective. A trigger-happy, atom-smashing, big question-asking physicist, who spends her days sifting though scraps of proton collisions for clues about the universe.

    Bose, an assistant professor of physics at Boston University’s College of Arts & Sciences, works at the Large Hadron Collider (LHC) in Switzerland, one of the most powerful particle accelerators ever built. The LHC smashes protons together 40 million times a second, and physicists like Bose sort through the wreckage. Bose is looking for particles (or their remains) that will substantiate (or dismiss) new theories that solve mysteries about the Big Bang and the nature of matter.

    In September 2014, Bose was appointed trigger coordinator for the Compact Muon Solenoid (or CMS) experiment at the LHC. She spoke with BU Research about what all those words mean, and why we should bother looking for “new physics” when the old physics seems to work just fine.

    c
    CMS

    BU Research: You were recently appointed the “trigger coordinator” for something called the CMS experiment. Can you explain what that is?

    Bose: Sure! At the LHC, we collide protons with protons to see what comes out of the collision, trying to find new particles and new physics. There are four major experiments and CMS is one of them. The name stands for Compact Muon Solenoid—a solenoid is a type of magnet, hence “solenoid” in the name. It’s a particle detector.

    How big is it?

    15 meters high (that’s about 50 feet) and 15 meters wide. A person next to it looks like a tiny little person.

    Then why is it called “compact”? It doesn’t seem very compact!

    Very good question. It’s a relative word, because it’s compact in comparison to another experiment, Atlas. Atlas is larger but less dense. CMS is more compact and dense.

    CERN ATLAS New
    ATLAS

    How does it all work?

    The LHC is like a huge racetrack. The protons go along in one direction, and then another beam of protons goes along in the other direction. Magnets bend them in a circular path. And most of the time these two beams are kept separated, except at four positions within this ring, where we have detectors with a different kind of magnet, which focuses the two beams together. And exactly at that point where this happens—where the two beams come together—is our CMS detector. The collision is happening right in the middle of the detector.

    How many protons collide?

    The beam has about 2,800 “bunches,” and a bunch has about 1,011 protons. So it’s a very intense bunch. But the collision point is very, very tiny, because the closer you can squeeze them, the more likely it is that an interesting collision will occur.

    How often do you collide them?

    The collisions are supposed to happen every 25 nanoseconds, which means—

    Continuously? All day?

    Yes, so 40 million times a second.

    That’s so much data!

    Yes, exactly. That’s the problem.

    I thought you did it, like, once a month or something.

    No. This is happening 40 million times a second and running over extended periods of time. Of course, I should clarify that for the past run, we ran at half that frequency. It was only 20 million times a second. But when we start taking data next year, it will be 40 million times a second. And this is the challenge. We just don’t have the kind of technology or the money to be writing out all of this data.

    What does it mean to “write out” data?

    Selecting and writing them to disk, so we can analyze it later. We need to cut down to a rate which is more manageable; I would say a few hundred events per second—at most, 1,000 events per second. So you want to go from 40 million times to 1,000. This has to be done in real time, and that’s where the trigger comes in. It’s literally a filter, or you’re “triggering” on interesting events. That’s where the name comes from.

    Now I get it—so you set up the filter beforehand?

    You set up the filter beforehand, and the filter fires every time an interesting event comes along. So that’s the trigger firing on something interesting.

    So it sees something interesting, it fires, and then that data is written.

    Right.

    And you’re the one who figures out the triggers!

    Yes! I lead the team that figures this out. It’s challenging, because whatever you say “no” to is literally going into the trash.

    That would be a terrible feeling.

    Yes. You want to make sure that all of the new physics, and the fun stuff, is not going into the trash. So we have a complicated trigger system. At the very first level, it makes some coarse decisions: Does this event have an electron? Does this event have a muon? Does the muon have a certain momentum? Does the electron have a certain momentum?

    And the reason it’s looking for those things is because those things would be boring? Or interesting?

    Muons and electrons are subatomic particles that are predicted to appear when certain other particles decay. We initially start with protons colliding with protons, so if energetic muons and electrons are produced, it indicates an interesting event. So the Level 1 part of the trigger has about three microseconds to make a decision. It doesn’t do detailed calculations. It doesn’t have that luxury. It just says, “This event seems interesting enough. I’m going to keep it.”

    Then comes the second level of the triggering system, which is called the High Level trigger. And this is essentially algorithms, which are trying to make more of an informed decision. They have a little bit more time, about 200 milliseconds per event, and can do some more detailed calculations. They can obtain the momentum with better resolution. They can try to figure out if two muons that they see come from a certain particle, which has a certain mass. Of course, all of this assumes that we understand what the new physics will be, which we don’t. This is the part that keeps people awake at night.

    You keep mentioning the “new” physics. What’s wrong with the old physics?

    It goes back to what’s called the Standard Model of particle physics. It’s essentially a set of very elegant equations that describe our current understanding of the universe. So we know, for example, that there are these light particles: the leptons, electrons, muons, taus; and associated with each one of these is a neutral particle called the neutrino. We also know that there are generations of quarks: there is up, down, strange, charm, bottom and top—or beauty and truth, as they’re sometimes called.

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

    We know all these very well. We also know that there are these forces, such as the magnetic force, the weak force, the strong force, and then the gravitational force. Now, each of these forces has an associated particle. One that is predicted, for example, is the graviton, which is a carrier of the gravitational force.

    Now, going back to your question: Why are we interested in other theories? The problem is that the Standard Model leaves us with some things that are not explained very well. Firstly, gravity. The Standard Model doesn’t quite include gravity in this full picture. And the carrier of gravity, which is this hypothetical particle called the graviton, we haven’t seen it. So the Standard Model does not include gravity, and that is something which people are not happy about, naturally.

    I can imagine.

    Then the other two big mysteries. At the very creation of the universe, right after the Big Bang, we had equal amounts of matter and antimatter. However, everything we see around us is primarily matter. So where has all the antimatter gone? Then the other big issue is that a large fraction of the universe is what’s called dark matter. Now, what is dark matter, really? Again, the Standard Model doesn’t quite explain that.

    So, to answer all of these big questions, you have to study these little tiny things.

    Yes, these big questions are driving the kind of physics we’re doing. These new theories, which try to answer these big questions, have various predictions about new particles, so we are actively searching for these new particles.

    Why do you like designing triggers?

    It’s a lot of responsibility, making sure that you’re not making a wrong decision. So I’ve always liked challenges. And these are very, very complicated detectors. And things can naturally go wrong in some part of the detector, and the first place this shows up is at the trigger. If you have bad electronics in a certain part of the detector, it will, for example, just start firing all the time. And so you will see it because the trigger rates will just go spiking up.

    And you’ll go, “Oh my God, we just found the new physics! Oh, never mind, we didn’t.”

    Exactly. This has happened a number of times. You get very excited because you start seeing spikes, and then you find out that no, this was faulty electronics.

    And then, for some reason, the people who work on the trigger are a certain kind of people. They are very passionate, they’re very dramatic, and the trigger meetings are dramatic places. People say, “I want certain kinds of triggers for my physics group, and you’ve got to give it to me or else I can’t do anything.”

    I had no idea that it was so operatic.

    [laugh] It’s always been like that. So it’s fun.

    See the full article here.

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    Boston University is no small operation. With over 33,000 undergraduate and graduate students from more than 130 countries, nearly 10,000 faculty and staff, 17 schools and colleges, and 250 fields of study, our two campuses are always humming, always in high gear.

    Boston University Campus
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  • richardmitnick 5:21 am on December 15, 2014 Permalink | Reply
    Tags: , , , Particle Accelerators,   

    From CERN: “CERN’s Large Hadron Collider gears up for run 2″ 

    CERN New Masthead

    12 Dec 2014
    Cian O’Luanaigh

    CERN today announced at the 174th session of the CERN Council that the Large Hadron Collider (LHC) is gearing up for its second three-year run. The LHC is the largest and most powerful particle accelerator in the world and the whole 27-kilometre superconducting machine is now almost cooled to its nominal operating temperature of 1.9 degrees above absolute zero. All teams are at work to get the LHC back online and the CERN Control Centre is in full swing to carry out all the requested tests before circulating proton beams again in March 2015. Run 2 of the LHC follows a 2-year technical stop that prepared the machine for running at almost double the energy of the LHC’s first run.

    lhc
    The Large Hadron Collider is preparing for running at higher energy in 2015 (Image: Maximilen Brice/CERN)

    “With this new energy level, the LHC will open new horizons for physics and for future discoveries,” says CERN Director-General Rolf Heuer. “I’m looking forward to seeing what nature has in store for us”.

    For the first time on 9 December 2014, the magnets of one sector of the LHC, one eighth of the ring, were successfully powered to the level needed for beams to reach 6.5 TeV, the operating energy for run 2. The goal for 2015 will be to run with two proton beams in order to produce 13 TeV collisions, an energy never achieved by any accelerator in the past.

    “After the huge amount of work done over the last two years, the LHC is almost like a new machine,” said CERN’s Director for Accelerators and Technology Frédérick Bordry. “Restarting this extraordinary accelerator is far from routine. Nevertheless, I’m confident that we will be on schedule to provide collisions to the LHC experiments by May 2015”.

    ALICE, ATLAS, CMS and LHCb, the four large experiments of the LHC, are also undergoing major preparatory work for run 2, after the long shutdown during which important programmes for maintenance and improvements were achieved. They will now enter their final commissioning phase.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

     
  • richardmitnick 6:49 pm on December 7, 2014 Permalink | Reply
    Tags: , , , , , Particle Accelerators,   

    From htxt.africa via FNAL: “Meet Claire Lee, a South African ATLAS physicist at CERN” 


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

    htxtdotafrica

    Anyone with even a passing interest in the sciences must have wondered what it’s like to work at the European Organisation for Nuclear Research, better known as CERN. Based in Switzerland, it’s one of the world’s largest and most respected centres for scientific research, birthplace of the worldwide web and home of the gigantic underground particle accelerator, the Large Hadron Collider (LHC).

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

    What wonders await those who join its ranks? What marvels must there be in the midst of such concentrated brain power?

    Since our chances of landing a job at CERN are probably limited to exciting opportunities in catering or sanitation, we figured it’s better to ask someone who does know. Someone like South African phyicist Claire Lee, who works right on ATLAS – one of the two elements of the LHC project that confirmed the existence of the Higgs boson in 2012.

    CERN ATLAS New
    ATLAS

    Lee has been involved with CERN since 2008 and has lived at the Swiss institute with her family for the past three and a half years. htxt.africa’s Tiana Cline sat down with Lee for a chat about all-things CERN, astrophysics and the elusive Higgs.

    How did you get interested in physics?

    Haha, this is a funny story. I’ve always loved science as long as I can remember (when I was very little I wanted to be an astronaut or an archaeologist), and have been fascinated with space since I could walk. But it really started in high school when I read the book Sphere by Michael Crichton. There was a character in the book who was an astrophysicist and I remember thinking to myself “Astrophysicist has to be about the coolest job title in the world, I want to be that!” So I set off to university with astrophysics as my final goal; however the astro-related projects that I ended up doing just didn’t seem to ever grab my interest. It was only in 2004, when for my Honours project I followed a basic version of what a friend was doing for his PhD in high energy nuclear physics, that I really started feeling the excitement.

    ac
    ATLAS Collaboration

    So science and physics were always a passion?

    In physics, High Energy Physics (HEP) is definitely my favourite, with a focus on Higgs and Beyond the Standard Model (BSM) physics. Our current theoretical knowledge is culminated in what is known as the Standard Model of Particle Physics, though we know that the theory is not complete (it doesn’t explain dark matter or dark energy, for example, nor the neutrino masses, and we have no idea how to incorporate gravity into the mix). So clearly there is lots of work still to do that will keep us hopefully busy with discoveries (or at least progress) for a while.

    In other fields, I do enjoy following the latest results in cosmology (such as the Planck vs BICEP2 saga, and AMS) and in particular where the fields of cosmology/astrophysics and particle physics overlap.

    And on a more personal note, neuroscience and the way the brain learns is fascinating too.

    Before jetting off to CERN, you studied in South Africa at both Wits and the University of Johannesburg as well as in Taiwan…

    I started off doing a BSc degree at Wits, I took Physics, Math, Applied Math and Chemistry in first year (2001). I hated Chemistry, so I dropped that first, took a second year Astronomy course, and ended up with Physics & Applied Math in 3rd year. I then did an Honours in Physics which was possibly one of the most fun years I’ve had in my life (we were a great class – 2004). At the end of that year I travelled to Virginia, USA for three weeks to work on an experiment at Jefferson Lab which became the subject of my MSc. I finally finished the MSc in 2009, also through Wits, and then moved to UJ where my supervisor had moved.

    As of 2007 South Africa wasn’t yet involved in the ATLAS experiment (though we had been working on ALICE, as well as ISOLDE and some of the smaller NA experiments for quite some time). But the annual South African Institute of Physics (SAIP) Conference we met Ketevi Assamagan, a US citizen originally from Togo, who was working at Brookhaven National Laboratory (BNL) on ATLAS. He had been invited to South Africa to speak at the conference – I think by Zeblon Vilakazi, member of the ALICE collaboration and (I think) director of iThemba LABS at the time. A group of us, especially my supervisor Prof Simon Connell and myself, were particularly interested in the type of physics ATLAS was doing, and a year later (2008) we flew to CERN to attend one of the ATLAS collaboration internal conferences, and meet with some of the heads of the experiment to discuss our involvement.

    The end of 2008 also saw the launch of the South Africa – CERN Programme which brought all the groups working on the various experiments together under one consortium.

    “Our current theoretical knowledge is culminated in what is known as the Standard Model of Particle Physics, though we know that the theory is not complete…” — Claire Lee, South African particle physicist

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

    ATLAS is an expensive experiment to keep running, and as such requires a financial commitment from its member institutions. There are yearly fees based on personnel (students are free), as well as a joining fee which equates to about R1M. The agreement was that we would have two years to account for the joining fee (from the DST), and BNL would cover our yearly fees in the meantime. In 2009 Prof Connell was at UJ, and Wits hired an ATLAS physicist Prof Trevor Vickey. Together they got their respective universities to commit to R250k each of the ATLAS joining fee, and the government to the other R500k, and in July 2010 the two universities were officially voted into the ATLAS collaboration as part of a single South African institute. (Since then UCT and then UKZN have joined the cluster.)

    I also lectured at UJ (first year calculus-based physics, extended programme) for two years from 2009-2011, and my son was born in May 2010.

    Thanks to popular TV shows like the Big Bang Theory, places like CERN and the idea of being a physicist has been somewhat romanticised. What is life at CERN really like?

    My best friend came to visit and described it as “Just like a huge university, with no undergrads” and that’s a pretty good explanation! There are so many facets to it, but for the most part you wouldn’t say you were at one of the world’s top scientific institutions just by walking around: most of the buildings were built to pretty utilitarian standards. We joke that all expense was spared above ground here, but it is part true as the most important part are the accelerators and detectors below ground. CERN itself employs less than 3 000 people – some scientists, but mostly staff in management, HR and engineering. There are about 10 000 people working on CERN projects in total, but most are attached to their own University or institute, and definitely not all at CERN at once!

    CERN has a large turnover of people, one of its missions is to train people in a worldwide environment and then let them take their experience back home, and so there is always a flux of especially young people moving in and out of the area (it gives you a whole new perspective on the concept of friends). A lot of people will move to CERN for a year or so of their PhD, especially at the start, to completely immerse themselves in the physics, and then move back to their home institute for the rest of their degree, just making occasional trips to CERN.

    It’s easy to just focus completely on the physics aspect, but of course there is a large social side too, and CERN has a number of clubs and societies for just about anything you can think of (sailing, dancing, karate, LGBT and so on). CERN also does a great deal of outreach – I have hosted a number of underground visits to ATLAS, and virtual visits to the control room, competed in, compared and judged the FameLab competition, as well as co-organised two standup comedy evenings!

    I think one of the things I really like about the CERN ethos in general is that it doesn’t matter who you are, what matters is what you are good at. And CERN has become pretty good at using the talents of their personnel to their best advantage (as long as you’re happy for them to be used, of course!).

    What has been the most interesting part about being at CERN since you moved to Switzerland at the end of June 2011?

    There have been so many interesting things – being on shift and looking after a part of the detector during the 2012 physics run was great, and the Higgs boson discovery and announcement was a huge highlight! But also the people – everyone I meet is pretty great in one way or another, and I have made some very close friends who are all amazing at what they do as well as in their extracurricular activities. It’s wonderful to be surrounded by so many exceptional people.

    Also, on a personal note, watching my son grow up in the French-speaking world has been amazing. He was just over a year old when we moved over, and at one and a half he started going to a French creche (my husband looked after him full-time for those first five months while I worked). He now speaks fluent French (WAY better than either of us) as well as English.

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    Lee hosting a “virtual visit” with Algeria from the ATLAS control room.

    A silly question – but what do you actually do on a day-to-day basis?

    My standard day is usually comprised of some mix of coding and attending meetings (either in person or remotely via Skype), interspersed with coffees and lunch. There are many different types of work one can do, since I am mostly on analysis this means coding, in C++ or Python, for example to select a particular subset of events that I am interested in from the full set of data. This usually takes a couple of iterations, where we slim down the dataset at each step and calculate extra quantities we may want to use for our selections.

    The amount of data we have is huge – petabytes of data per year stored around the world at various high performance computing centres and clusters. It’s impossible to have anything but the smallest subset available locally – hence the iterations – and so we use the LHC Computing Grid (a specialised worldwide computer network) to send our analysis code to where the data is, and the code runs at these different clusters worldwide (most often in a number of different places, for different datasets and depending on which clusters are the least busy at the time). At the ultimate or penultimate step our personalised datasets are usually small enough to put somewhere local (either on a laptop or university cluster) from which we can make nice-looking plots etc.

    Various meetings happen all day every day on ATLAS, though of course you only attend the ones relevant to the work you are doing as it would be impossible otherwise! Whether it’s an analysis- or performance-related meeting (analysis is, eg, a particular physics analysis, such as a Higgs measurement, while performance studies relate to the measurement and calibration of the physics objects – like electrons – that are used in the analyses) people will present their most recent work, and usually there will be some discussion on how to move forward.

    a
    View of the ATLAS cavern side A beginning of February 2008, before the lowering of the Muon Small Wheels.

    And on the ATLAS Experiment?

    The ATLAS experiment is one of the four large experiments at the LHC. It is also the biggest of the four detectors (in volume) and like CMS, is a general-purpose detector, designed to detect all particles from the high energy proton-proton collisions. This allows ATLAS to cover many different aspects of physics, from measurements of the Higgs boson to searches for new physics. The detector itself is built like a giant three-dimensional puzzle of different detector components, with each part measuring a different aspect of the final-state particles from the collisions as they move through the detector.

    To be able to do any analysis, after the data has been recorded the events have to be reconstructed, meaning that the signals from the different parts of the detector are combined and fitted into objects such as electrons, muons, jets etc. Analyses can then select events based on the objects they have in them – a Higgs boson decaying to four leptons, for example, would then select events containing electrons and/or muons.

    Other quantities based on these objects are also calculated, such as the missing transverse momentum, which is the vector sum of the energies of all the particles in the event, measured by the calorimeters (and comes about due to conservation of momentum). This is important for events where we have particles that we do not detect, such as neutrinos, and so the only way we know they are there is by noticing an imbalance in the total momentum (the neutrino would then be going in the other direction). A very large amount of missing momentum, by the way, could also be a signal for a supersymmetric particle, so this quantity is used in a number of analyses.

    I’ve done various things – I worked as an online expert for one of the ATLAS calorimeters, for example, making sure that it was running properly and able to take good data while the collisions were happening. This sometimes involved being called in the middle of the night to solve problems!

    But one of my main tasks, and what my thesis is on, has been developing a new and complimentary method of measuring the missing transverse momentum, only this time we use particle track momenta rather than calorimeter energy measurements. This method has proven to be very useful, especially when combining the result with the “traditional” measurement from the calorimeter, and is used in various Higgs analyses to help separate signal from background.

    We’ve heard that there are over 3 000 physicists working on ATLAS. Who are the other African scientists working at the institute? It must be interesting working with such a diverse group of people.

    Ketevi Assamagan (who is now a co-supervisor of mine), for example, was the first ATLAS physicist I ever met. My other supervisor (Rachid Mazini) works for Taiwan but he is originally from Morocco. And of course although the groups have grown in the past few years, the High Energy Physics community in South Africa is pretty small, and we all fall under the SA-CERN programme, so we know each other quite well.

    There are over 100 different nationalities represented on ATLAS, so you become quite culturally-aware, especially when it comes to being sensitive of others’ commitments around things like Thanksgiving, Ramadan, Christmas, etc, as well as personal issues like kids. I’ve found that people are in general pretty tolerant, and as long as your work is coming along well you are pretty free to work as you see fit.

    swh
    Several hundred of the 1 700 scientists contributing to the LHC accelerator and experiments gathered in CERN’s building 40.

    Back to South Africa – are you positive about the state of science/physics education here?

    Yes and no. I think universities are doing a good job, mostly, we do have some top quality researchers here in South Africa and are able to place well on the international scale. On the other hand, the quality of the schooling is going down terribly, and some of the students gaining university entrance nowadays and qualifying for these courses know extremely little. This only puts pressure on the universities, increasing lecturers’ loads, which is unfortunate.

    Science is tough generally, and the sort of high-pressure environment that ATLAS is even tougher, so you need to have some internal reason to continue doing what you do. Second, making sure you have really supportive people around you also is important, people who encourage you to succeed and are there for you when you need them. And finally, it’s about making contacts; attending meetings (in person if you can) and talking to people and presenting your work regularly, as well as more “fun” stuff like outreach, all helps to get people to know who you are and what you can do.

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
  • richardmitnick 12:04 pm on December 4, 2014 Permalink | Reply
    Tags: , , , , Particle Accelerators, ,   

    From FNAL- “Frontier Science Result: CDF Wading through the swamp to measure top quark mass” 


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

    Thursday, Dec. 4, 2014
    edited by Andy Beretvas

    Even after the discovery of the Higgs boson, the top quark is still a focus of attention because of its peculiar position of being the heaviest quark in the Standard Model and for its possible role in physics beyond the Standard Model.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    If the Standard Model is correct, the stability of the vacuum strongly depends on the mass of the Higgs boson and the top quark mass. In this context, scientists favor the scenario that the universe is in a metastable state. A precision measurement of the top quark mass helps to better determine the relative stability of that state in this scenario.

    At the Tevatron, top quarks were produced, mostly in pairs, only once in about 10 billion collisions. They decayed right away into a W boson and a b quark. In the most abundant and yet most challenging scenario, the final state contains six collimated sprays of particles, called jets, two of which likely originated from the b quarks, with peculiar, identifiable characteristics (allowing them to be “b-tagged”). This decay mode is usually called the all-hadronic channel, for which the signal is swamped by a background associated to the production of uninteresting multijet events, which were about a factor of 1,000 more abundant than the signal events.

    FNAL Tevatron
    Tevatron

    This new analysis uses the full CDF Run II data set.
The set contains nearly twice the number of top quark pairs as seen in our previous measurement. The analysis uses an improved simulation and relies on there being at least one b-tagged jet. An important part of the analysis is to minimize the uncertainty in our measurement of jet scale energies. Exploiting the expected behavior of top-antitop signal events, the huge background can be tamed through finely tuned requirements, yielding about 4,000 events, where about one event out of three is expected from the signal. The all-hadronic final state can then be fully reconstructed using the energies of the six jets, and the mass of the top quark can be derived comparing the data to simulations produced for different input values of the top quark mass (see the [below] figure).

    i
    The black dots plot the distribution of the reconstructed top mass for events containing one or more b-tags. The distribution is compared to the expected yield for background and signal events, normalized to the best fit.

    FNAL CDF
    CDF

    This procedure yields a value of 175.1 ± 1.2 (stat) ± 1.6 (sys) GeV/c2 for the top quark mass, with a 1 percent relative precision. This measurement complements the results obtained by CDF in other channels. Our measurement is consistent with the current world average (which includes our previous measurement in the all-hadronic channel), obtained from measurements by ATLAS, CDF, CMS and DZero. The top quark mass world average is 173.3 ± 0.8 GeV/c2.

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

    FNAL DZero
    DZero

    See the full article here.

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics.

     
  • richardmitnick 10:28 pm on December 3, 2014 Permalink | Reply
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    From isgtw: “Volunteer computing: 10 years of supporting CERN through LHC@home” 


    international science grid this week

    December 3, 2014
    Andrew Purcell

    LHC@home recently celebrated a decade since its launch in 2004. Through its SixTrack project, the LHC@home platform harnesses the power of volunteer computing to model the progress of sub-atomic particles traveling at nearly the speed of light around the Large Hadron Collider (LHC) at CERN, near Geneva, Switzerland. It typically simulates about 60 particles whizzing around the collider’s 27km-long ring for ten seconds, or up to one million loops. Results from SixTrack were used to help the engineers and physicists at CERN design stable beam conditions for the LHC, so today the beams stay on track and don’t cause damage by flying off course into the walls of the vacuum tube. It’s now also being used to carry out simulations relevant to the design of the next phase of the LHC, known as the High-Luminosity LHC.

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

    “The results of SixTrack played an essential role in the design of the LHC, and the high-luminosity upgrades will naturally require additional development work on SixTrack,” explains Frank Schmidt, who works in CERN’s Accelerators and Beam Physics Group of the Beams Department and is the main author of the SixTrack code. “In addition to its use in the design stage, SixTrack is also a key tool for the interpretation of data taken during the first run of the LHC,” adds Massimo Giovannozzi, who also works in CERN’s Accelerators and Beams Physics Group. “We use it to improve our understanding of particle dynamics, which will help us to push the LHC performance even further over the coming years of operation.” He continues: “Managing a project like SixTrack within LHC@home requires resources and competencies that are not easy to find: Igor Zacharov, a senior scientist at the Particle Accelerator Physics Laboratory (LPAP) of the Swiss Federal Institute of Technology in Lausanne (EPFL), provides valuable support for SixTrack by helping with BOINC integration.”

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    Volunteer computing is a type of distributed computing through which members of the public donate computing resources (usually processing power) to aid research projects. Image courtesy Eduardo Diez Viñuela, Flickr (CC BY-SA 2.0).

    Before LHC@home was created, SixTrack was run only on desktop computers at CERN, using a platform called the Compact Physics Screen Saver (CPSS). This proved to be a useful tool for a proof of concept, but it was first with the launch of the LHC@home platform in 2004 that things really took off. “I am surprised and delighted by the support from our volunteers,” says Eric McIntosh, who formerly worked in CERN’s IT Department and is now an honorary member of the Beams Department. “We now have over 100,000 users all over the world and many more hosts. Every contribution is welcome, however small, as our strength lies in numbers.”

    Virtualization to the rescue

    Building on the success of SixTrack, the Virtual LHC@home project (formerly known as Test4Theory) was launched in 2011. It enables users to run simulations of high-energy particle physics using their home computers, with the results submitted to a database used as a common resource by both experimental and theoretical scientists working on the LHC.

    Whereas the code for SixTrack was ported for running on Windows, OS X, and Linux, the high-energy-physics code used by each of the LHC experiments is far too large to port in a similar way. It is also being constantly updated. “The experiments at CERN have their own libraries and they all run on Linux, while the majority of people out there have common-or-garden variety Windows machines,” explains CERN honorary staff member of the IT department and chief technology officer of the Citizen Cyberscience Centre Ben Segal. “Virtualization is the way to solve this problem.”

    The birth of the LHC@home platform

    In 2004, Ben Segal and François Grey , who were both members of CERN’s IT department at the time, were asked to plan an outreach event for CERN’s 50th anniversary that would help people around the world to get an impression of the computational challenges facing the LHC. “I had been an early volunteer for SETI@home after it was launched in 1999,” explains Grey. “Volunteer computing was often used as an illustration of what distributed computing means when discussing grid technology. It seemed to me that it ought to be feasible to do something similar for LHC computing and perhaps even combine volunteer computing and grid computing this way.”

    “I contacted David Anderson, the person behind SETI@Home, and it turned out the timing was good, as he was working on an open-source platform called BOINC to enable many projects to use the SETI@home approach,” Grey continues. BOINC (Berkeley Open Infrastructures for Network Computing)is an open-source software platform for computing with volunteered resources. It was first developed at the University of California, Berkeley in the US to manage the SETI@Home project, and uses the unused CPU and GPU cycles on a computer to support scientific research.

    “I vividly remember the day we phoned up David Anderson in Berkeley to see if we could make a SETI-like computing challenge for CERN,” adds Segal. “We needed a CERN application that ran on Windows, as over 90% of BOINC volunteers used that. The SixTrack people had ported their code to Windows and had already built a small CERN-only desktop grid to run it on, as they needed lots of CPU power. So we went with that.”

    A runaway success

    “I was worried that no one would find the LHC as interesting as SETI. Bear in mind that this was well before the whole LHC craziness started with the Angels and Demons movie, and news about possible mini black holes destroying the planet making headlines,” says Grey. “We made a soft launch, without any official announcements, in 2004. To our astonishment, the SETI@home community immediately jumped in, having heard about LHC@home by word of mouth. We had over 1,000 participants in 24 hours, and over 7,000 by the end of the week — our server’s maximum capacity.” He adds: “We’d planned to run the volunteer computing challenge for just three months, at the time of the 50th anniversary. But the accelerator physicists were hooked and insisted the project should go on.”

    Predrag Buncic, who is now coordinator of the offline group within the ALICE experiment, led work to create the CERN Virtual Machine in 2008. He, Artem Harutyunyan (former architect and lead developer of CernVM Co-Pilot), and Segal subsequently adopted this virtualization technology for use within Virtual LHC@home. This has made it significantly easier for the experiments at CERN to create their own volunteer computing applications, since it is no longer necessary for them to port their code. The long-term vision for Virtual LHC@home is to support volunteer-computing applications for each of the large LHC experiments.
    Growth of the platform

    The ATLAS experiment recently launched a project that simulates the creation and decay of supersymmetric bosons and fermions. “ATLAS@Home offers the chance for the wider public to participate in the massive computation required by the ATLAS experiment and to contribute to the greater understanding of our universe,” says David Cameron, a researcher at the University of Oslo in Norway. “ATLAS also gains a significant computing resource at a time when even more resources will be required for the analysis of data from the second run of the LHC.”

    CERN ATLAS New
    ATLAS

    ATLAS@home

    Meanwhile, the LHCb experiment has been running a limited test prototype for over a year now, with an application running Beauty physics simulations set to be launched for the Virtual LHC@home project in the near future. The CMS and ALICE experiments also have plans to launch similar applications.

    CERN LHCb New
    LHCb

    CERN CMS New
    CMS

    CERN ALICE New
    ALICE

    An army of volunteers

    “LHC@home allows CERN to get additional computing resources for simulations that cannot easily be accommodated on regular batch or grid resources,” explains Nils Høimyr, the member of the CERN IT department responsible for running the platform. “Thanks to LHC@home, thousands of CPU years of accelerator beam dynamics simulations for LHC upgrade studies have been done with SixTrack, and billions of events have been simulated with Virtual LHC@home.” He continues: “Furthermore, the LHC@home platform has been an outreach channel, giving publicity to LHC and high-energy physics among the general public.”

    See the full article here.

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    iSGTW is an international weekly online publication that covers distributed computing and the research it enables.

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

    In its current incarnation, iSGTW is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

    You can read iSGTW via our homepage, RSS, or email. For the complete iSGTW experience, sign up for an account or log in with OpenID and manage your email subscription from your account preferences. If you do not wish to access the website’s features, you can just subscribe to the weekly email.”

     
  • richardmitnick 8:10 pm on December 1, 2014 Permalink | Reply
    Tags: , , , , , Particle Accelerators,   

    From Scientific American- Don Lincoln of Fermilab “U.S. Particle Physics Program Aims for the Future” 

    Scientific American

    Scientific American

    November 25, 2014

    FNAL Don Lincoln
    Dr. Don Lincoln

    n the last few years, stories have abounded in the press of the successes of the Large Hadron Collider, most notably the discovery of the Higgs boson. This has led some to speculate that European research is ascendant while U.S. research is falling behind. While there is no argument that U.S. particle physics budgets have shrunk over the past decade, it is also inarguable that America is still huge player in this fascinating research sector, collaborating on projects in Europe and Asia while pursuing a strong domestic program as well.

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

    To properly appreciate the breadth of the U.S.’s contribution to particle physics research, one must distinguish between the international program and the domestic one. The international program is currently (and appropriately) focused mostly on the LHC. The ring-shaped collider is, without a doubt, an amazing piece of equipment. It is 17 miles around, took a quarter century to plan and build, cost about $10 billion, and requires about 10,000 scientists to operate and study the data it generates. Four distinct experiments (ALICE, ATLAS, CMS and LHCb) were built to use the LHC to investigate some of mankind’s oldest scientific questions.

    CERN ALICE New
    ALICE

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

    CERN LHCb New
    LHCb

    Physicists employed by U.S. universities and national laboratories comprise about a third of the LHC experimental program, making the U.S. the single largest country involved in the project. Although the CERN laboratory itself employs more LHC scientists than any other single institution, America’s Fermilab and Brookhaven National Laboratory are uncontested seconds for CMS and ATLAS, respectively. American physicists lead many analysis efforts and the CMS collaboration even elected Professor Joe Incandela of the University of California, Santa Barbara to be the group leader.

    fnal
    Fermilab’s Main Ring and Main Injector as seen from the air. (Credit: Reidar Hahn/Fermilab)

    While there is no denying the attractiveness of the LHC as a scientific opportunity, U.S. scientists also pursue an active and vibrant U.S. domestic program. Fermilab serves as the hub for the American particle physics community and the laboratory’s accelerators, both present and future, are helping scientists blaze new trails into the fascinating subatomic world.

    Because the LHC is firmly ensconced as the highest energy facility in the world for the foreseeable future, Fermilab is focusing on a different technique to delve into the fundamental rules of the universe. By choosing to concentrate on making the highest intensity particle beams ever achieved, the U.S.’s domestic program is able to investigate some of the rarest phenomena ever imagined at energy scales that far exceed those accessible at the LHC. High energy means that individual beam particles are moving at unprecedented speeds, while high intensity means many particles focused on a tiny area, much like a magnifying lens can focus light. When many particles are brought into tight proximity, there is a small chance that a quantum mechanical fluctuation will allow an extremely unlikely and ultra-high energy interaction to occur.

    It’s easy to explain to people why building a higher energy facility is valuable, but understanding why higher intensity beams is a leading research strategy is a little more difficult and requires two insights. The first and simpler insight is to realize that in particle physics, we look for rare collisions between beams of particles. The reason we look for rare ones is that the common ones have been studied already.

    bnl
    The central campus of Brookhaven National Laboratory. The National Synchrotron Light Source II, under construction at the time of this photo, is at bottom, right. The 3.8-kilometer circumference ring of the Relativistic Heavy Ion Collider can be seen in the distance at the top of the frame. (Credit: Brookhaven National Laboratory)

    To observe the rarest collisions, one must simply make a lot of collisions and wait. It’s similar to trying to win the lottery. If you buy one ticket, you are unlikely to succeed, but if you buy many tickets there is a much higher chance that you have bought a winner.

    The more subtle insight hinges on the principles of physics, specifically quantum mechanics. While it is a firm rule of classical physics that energy is conserved, this rule is not so rigidly observed in the quantum realm. According to the tenets of the Heisenberg Uncertainty Principle, energy can simply appear, as long as it disappears quickly enough. Further, the larger the temporary energy imbalance, the shorter the duration. Thus, because they persist for so short a time, the large energy imbalances are very rare. And, as I have noted above, to study very rare processes, one must employ very intense beams.

    Using the current Fermilab accelerator complex, physicists are studying the interactions of neutrinos with matter. Neutrinos only experience the weak nuclear force and can pass through a lot of matter without interacting. To give a sense of scale, the sun constantly emits neutrinos. If we were determined to stop half of them, we’d need a wall composed of solid lead that is five light years thick! Given this reluctance to interact, the only way to ensure enough neutrino interactions to study is to generate incredibly intense beams and analyze them with massive particle detectors.

    The Fermilab MINOS and NOvA experiments shoot unprecedentedly bright beams of neutrinos from Chicago to northern Minnesota to study an interesting phenomenon called neutrino oscillations. Neutrinos are unique in that they can change their identity, vaguely as if an electron could change into a proton and back. It is hoped that understanding this oscillatory behavior might explain why the universe is made solely of matter when we believe that matter and antimatter existed in equal quantities when the universe began.

    FNAL NOvA
    FNAL NOvA

    mu
    The muon g-2 storage ring arrives at Fermilab, near Chicago, in July 2013 after a cross-country trip from Brookhavn National Laboratory on Long Island, New York. (Credit: Reidar Hahn/Fermilab)

    A second bright star in the constellation of U.S. particle physics research is the use of Fermilab’s accelerator complex to study muons, the heavy cousins of electrons. Scientists of the Muon g-2 experiment will measure the magnetic moment of muons. Earlier measurements at the Brookhaven National Laboratory were very precise – with eight digits of precision. However, there is a tantalizing tension between data and theoretical predictions. While both measurement and prediction are exquisitely precise, the two numbers disagree slightly. This disagreement is small, but is about three and a half times larger than the combined experimental and theoretical uncertainty. This discrepancy could signify the onset of new physics, which could involve supersymmetry, muon substructure or something entirely unexpected. Because Fermilab can generate more intense beams of muons than Brookhaven, the g-2 apparatus was moved from Long Island, New York to Chicago to investigate this question more thoroughly.

    Supersymmetry standard model
    Standard Model of Supersymmetry

    Yet another interesting question that has been investigated relates to unconventional muon decays. Most muons decay into electrons and two neutrinos, however there are reasons to suspect that perhaps muons might decay into electrons without neutrinos. The Mu2e experiment at Fermilab is scheduled to start recording data in a couple of years and this experiment will be sensitive to energy scales far higher than the LHC can achieve. Since neutrinos transform into other types of neutrinos and quarks can change into other quarks, physicists think that the transition of muons into electrons might be possible. Because this decay is expected to be very rare (if it exists at all), this is another reason to make high intensity muon beams.

    A multi-year study of the pressing physics questions by the entire U.S. particle physics community resulted in a firm recommendation to upgrade the Fermilab accelerator complex to further increase the amount of beam it can supply. Thus, the long term plan for the Fermilab laboratory is to increase the intensity of its neutrino beams by at least 50 percent and shoot these beams off to a detector to be located in South Dakota. Because neutrinos change their identity (i.e. oscillate) in flight, having detectors at different distances from Fermilab gives a complementary view of neutrino oscillations and it will shed more light on the phenomenon.

    FNAL LBNE

    But the U.S. community hasn’t forgotten the energy frontier. Eventually, there will be an accelerator that replaces the LHC as the energy leader. It will be a long time before any decisions are made on where that facility might be located (or even what kinds of beams will be needed: protons or electrons). But, to be prepared, several institutions across the U.S. are expanding their accelerator development programs. Whether the future facility is located in the U.S., Europe or Asia, U.S. accelerator scientists will be heavily engaged in developing the required technology.

    Even with tight budgets, the American particle physics community has continued to have a huge impact in humankind’s investigations of some of the oldest scientific questions, and continued support is key to maintaining this leading role.

    See the full article here.

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    Scientific American, the oldest continuously published magazine in the U.S., has been bringing its readers unique insights about developments in science and technology for more than 160 years.

     
  • richardmitnick 9:56 pm on November 27, 2014 Permalink | Reply
    Tags: , , , , Particle Accelerators,   

    From CERN: “How bright is the LHC?” 

    CERN New Masthead

    Nov 27, 2014
    l

    The LHCb Collaboration has published the results of a luminosity calibration with a precision of 1.12%. This is the most precise luminosity measurement achieved so far at a bunched-beam hadron collider.

    lm
    LHC beam results

    The absolute luminosity at a particle collider. is not only an important figure of merit for the machine, it is also a necessity for determining the absolute cross-sections for reaction processes. Specifically, the number of interactions, N, measured in an experiment depends on the value of cross-section σ and luminosity L, N = σL, so the precision obtained in measuring a given cross-section depends critically on the precision with which the luminosity is known. The luminosity itself depends on the number of particles in each collider beam and on the size of overlap of both beams at the collision point. At the LHC, dedicated instruments measure the beam currents, and hence the number of particles in each colliding beam, while the experiments measure the size of overlap of the beams at the collision point.

    A standard method to determine the overlap of the beams is the van der Meer scan, invented in 1968 by Simon van der Meer to measure luminosity in CERN’s Intersecting Storage Rings, the world’s first hadron collider. This technique, which involves scanning the beams across each other and monitoring the interaction rate, has been used by all of the four large LHC experiments. However, LHCb physicists proposed an alternative method in 2005 – the beam-gas imaging (BGI) method – which they successfully applied for the first time in 2009. This takes advantage of the excellent precision of LHCb’s Vertex Locator, a detector that is placed around the proton–proton collision point. The BGI method is based on reconstructing the vertices of “beam-gas” interactions, i.e. interactions between beam particles and residual gas nuclei in the beam pipe to measure the angles, positions and shapes of the individual beams without displacing them.

    To date, LHCb is the only experiment capable of using the BGI method. The technique involves calibrating the luminosity during special measurement periods at the LHC, and then tracking relative changes through changes in the counting rate in different sub-detectors. However, the vacuum pressure in the LHC is so low that for the technique to work with high precision, the beam–gas collision rate was increased by injecting neon gas into the LHC beam pipe during the luminosity calibration periods. This allowed the LHCb physicists to obtain precise images of the shapes of the individual beams, as illustrated in the left and middle graphs of the figure, which unraveled subtle but important features of the distributions of beam particles. By combining the beam–gas data with the measured distribution of beam–beam interactions, which provides the shape of the luminous region (the right graph in the figure), an accurate calibration of the luminosity was achieved.

    The beam–gas data also revealed that a small fraction of the beam’s charge is spread outside of the expected (i.e. “nominal”) bunch locations. Because only collisions of protons located in the nominal bunches are included in physics measurements, it was important to measure which fraction of the total beam current measured with the LHC’s current monitors participated in the collisions, i.e. contributed to the luminosity. Only LHCb could measure this fraction with sufficient precision, so the results of LHCb’s measurements of the fraction of charge outside the nominal bunch locations – the so-called “ghost” charge – were also used by the ALICE, ATLAS and CMS experiments.

    For proton–proton interactions at 8 TeV, a relative precision of the luminosity calibration of 1.47% was obtained using van der Meer scans and 1.43% using beam–gas imaging, resulting in a combined precision of 1.12%. The BGI method has proved to be so successful that it will now be used to measure beam sizes as part of monitoring and studying the LHC beams. Dedicated equipment will be installed in a modified region of the LHC ring near Point 4. This system, dubbed the Beam-Gas Vertexing system (BGV), is being developed by a collaboration from CERN, EPFL and RTWH Aachen. It includes a gas-injection system and a scintillating-fibre tracker telescope, which are expected to be commissioned with beam in 2015.

    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

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

     
  • richardmitnick 10:33 am on November 27, 2014 Permalink | Reply
    Tags: , , , New York University, Particle Accelerators,   

    From phys.org: “It’s particle-hunting season! NYU scientists launch Higgs Hunters Project” 

    physdotorg
    phys.org

    November 26, 2014
    No Writer Credit

    New York University scientists and their colleagues have launched the Higgs Hunters project, which will allow members of the general public to study images recorded at the Large Hadron Collider and to help search for previously unobserved particles.

    p
    A graphic shows particle traces extending from a proton-proton collision at the Large Hadron Collider in 2012. The event shows characteristics expected from the decay of the Standard Model Higgs boson to a pair of photons

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

    The Higgs Hunters project follows the successful 2012 discovery of the famous Higgs boson particle, a sub-atomic particle that plays a key role in our understanding of the Universe, at the CERN laboratory near Geneva, where the collider is based.

    In 2013, Peter Higgs and François Englert received the Nobel Prize for Physics in recognition of their work to develop the theory of what is now known as the Higgs field, which gives elementary particles mass.

    The project will also include researchers from the University of Oxford, the University of Birmingham, the Zooniverse project, and the ATLAS experiment at CERN.

    CERN ATLAS New
    ATLAS at CERN’s LHC

    “Writing computer algorithms to identify these particles is tough, so we’re excited to see how much better we can do when people help us with the hunt,” observes Andy Haas, an assistant professor of physics at NYU and one of the project’s collaborators.

    “Having found the Higgs Boson particle, now we want to know how it works,” adds Alan Barr, a professor of particle physics at the University of Oxford, and lead scientist of the Higgs Hunters project. “To do that, we’d like you to look at these pictures of collisions and tell us what you can see.”

    The project scientists are searching for previously unobserved microscopic particles that might be created when the Higgs Boson particle decays. The new particles are predicted to leave tell-tale tracks inside the ATLAS experiment, which computer programs find difficult to identify, but which human eyes can often pick out.

    A successful detection would be a huge leap forward for particle physics, researchers say, as any new particles would lie beyond the “Standard Model” – the current best theory of the fundamental constituents of the universe.

    sm
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    For more, please visit http://www.higgshunters.org .

    The project was funded by a Google Global Impact Award, the Science and Technology Research Council of the United Kingdom, and the National Science Foundation, which supports ATLAS work at NYU that includes research and education.

    See the full article here.

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 11:57 am on November 25, 2014 Permalink | Reply
    Tags: , , , , Particle Accelerators,   

    From Times Beacon record via BNL: “BNL’s Pleier takes next steps after Higgs-boson” 

    t

    Brookhaven Lab

    November 19, 2014
    Daniel Dunaief

    mp
    Marc-Andre Pleier photo from BNL

    While the United States was celebrating Independence Day two years ago, a group of people were cheering the discovery of something they had spent almost half a century seeking. Physicists around the world were convinced the so-called Higgs boson particle existed, but no one had found clear-cut evidence of it.

    At a well-attended press conference, scientists hailed the discovery, while recognizing the start of a new set of experiments and questions.

    As a part of the ATLAS team, Marc-Andre Pleier knew what the group was set to announce. He was very excited “to see the signal confirmed by an independent measurement.” Two years later, Pleier, a physicist at Brookhaven National Laboratory and a part of a group of more than 3,000 scientists from around the world, are tackling the next set of questions.

    ca

    The discovery “points to the Standard Model [of particle physics] being correct, but to know this we need to understand this new particle and its properties a lot better than we do now.”

    s,
    The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column, and the Higgs boson in the fifth.

    According to the Standard Model of particle physics, the Big Bang beginning to the universe should have created equal parts matter and antimatter. If it did, the two opposite energies would have annihilated each other into light. An imbalance, however, resulted in a small fraction of matter surviving, forming the visible universe. The origin of this imbalance, however, is unknown, Pleier said.

    “We know the Standard Models is incomplete,” he said, because there are observations of dark matter, dark energy and the antimatter/matter asymmetry in the universe that can’t be explained by this model. “We can test this” next chapter.

    Cosmic Microwave Background  Planck
    Cosmic Background Radiation per ESA/Planck

    The process Pleier studies allows him to test whether the particle is doing its job as expected. In addition to analyzing data, Pleier also has “major responsibility in upgrading the detector,” said Hong Ma, a group leader in the Physics Department at BNL who recruited Pleier to join BNL in 2009.

    Scientists at the [Large] Hadron Collider in Switzerland and at BNL and elsewhere are studying interactions that are incredibly rare among particles.

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

    Pleier is searching for interactions of vector bosons, which have spin values of one and are extremely large in the world of bosons. He is looking for cases where two W bosons interact with each other.

    “Only one event out of a hundred trillion events will be of interest to me,” said Pleier. Comparing those numbers to the world of biology, Pleier likened that to finding a single cell in an entire human body.

    In 2012, the Hadron Collider produced 34 such interactions. The collider produces about 40 million pictures per second. To find the ones that might hold promising information, scientists like Pleier need to use a computing grid. BNL is one of only 10 tier 1 centers for ATLAS and the only one in the United States. Thus far, scientists have been able to look at these collisions from energies at 8 trillion electron volts. They hope to measure similar data at 13 trillion electron volts next year.

    Ma said the increased energy of the collider will “put the Standard Model to an unprecedented level of tests,” allowing scientists to “measure the properties of Higgs boson to a higher precision.”

    Growing up in Germany, Pleier said he loved playing with Legos to see how things worked. He helped fix his own toys. When he was older, he worked to repair a motor bike his uncle had.

    What he’s doing now, he said, is exploring the fundamental building blocks of matter and their interactions. He likened it to examining the “construction kit” for the universe. While he’s a physicist, Pleier explained that he’s a Christian. “Some people think it has to be in conflict, but, for me, it clearly is not,” he said. “Each discovery adds to my admiration for God’s creation.”

    A resident of Middle Island, Pleier lives with his wife Heather, an English teacher who is staying home for now to take care of their three children.

    Pleier and Ma emphasized that the work at the collider is a collaborative effort involving scientists from institutions around the world.

    Michael Kobel, a professor at TU Dresden, head of the Institute for Particle Physics and Dean of Studies in the Department of Physics who has known Pleier for about nine years, likened the process of studying the high energy particles to exploring a cave, where scientists “get more light to look deeper” into areas that were in the dark before. Researchers, he said, are just entering this cave of knowledge, with “a lot of corners yet to be explored.”

    See the full article here.

    BNL Campus

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    One of ten national laboratories overseen and primarily funded by the Office of Science of the U.S. Department of Energy (DOE), Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies and national security. Brookhaven Lab also builds and operates major scientific facilities available to university, industry and government researchers. The Laboratory’s almost 3,000 scientists, engineers, and support staff are joined each year by more than 5,000 visiting researchers from around the world.Brookhaven is operated and managed for DOE’s Office of Science by Brookhaven Science Associates, a limited-liability company founded by Stony Brook University, the largest academic user of Laboratory facilities, and Battelle, a nonprofit, applied science and technology organization.
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  • richardmitnick 5:56 pm on November 23, 2014 Permalink | Reply
    Tags: , , , , Particle Accelerators,   

    From LHCb at CERN: “The proton beam knocks at the LHC door” 

    CERN New Masthead

    23 November 2014
    No Writer Credit

    The LHCb collaboration took proton interaction data this weekend

    team
    LHCb is an experiment set up to explore what happened after the Big Bang that allowed matter to survive and build the Universe we inhabit today.

    The proton beam knocked at the LHC’s very solid door this weekend and found it still closed, but nonetheless managed to provide the LHCb collaboration with very interesting data. The CERN accelerator system (see video) is now fully operational, except for the LHC collider itself. This past weekend, CERN accelerator system operators tested the two transfer lines between the SPS and LHC. One of these lines ends with a so-called beam stopper known as the “TED”, located at the end of the line about 300m from the LHCb detector. The TED is currently closed, and so absorbed the proton beam before it could enter the LHC. However many muons were produced during the absorption process, and these muons passed through the TED and traversed the LHCb detector.

    This “beam dump” experiment therefore created an excellent opportunity for LHCb physicists and engineers to commission the LHCb detector and data acquisition system. The collected data are also useful for detector studies and alignment purposes (i.e. determining the relative geometrical locations of the different sub-detectors with respect to each other).

    gr
    The image shows the shift leader, run coordinator, spokesperson and sub-detector experts in front of the LHCb data acquisition computer screens.

    LHCb took its last collision data on 14th February 2013. The two year Long Shutdown 1 (LS1) period that followed has been used for an extensive program of consolidation and maintenance (see 24 January 2014 “underground” news). Collisions are expected to resume again in Spring 2015.

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

    See the full article, with video, here.

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    Stem Education Coalition

    Meet CERN in a variety of places:

    Cern Courier

    THE FOUR MAJOR PROJECT COLLABORATIONS

    ATLAS
    CERN ATLAS New
    ALICE
    CERN ALICE New

    CMS
    CERN CMS New

    LHCb
    CERN LHCb New

    LHC

    CERN LHC New

    LHC particles

    Quantum Diaries

     
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