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  • richardmitnick 12:53 pm on March 27, 2015 Permalink | Reply
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    From CMS at CERN/LHC: “CMS is never idle” 

    CERN New Masthead

    2015-03-27
    André David and Dave Barney

    CERN CMS New II

    1
    Before proton collisions take place again at the LHC, the CMS detector has been looking at the result of collisions of cosmic particles high up in the atmosphere. This event display shows the track of a muon that reached the CMS detector 100 m underground and passed through the muon chambers (in red) and the silicon tracker (in yellow). Muons as this one are used to calibrate the detector in advance of proton collisions.

    CMS is eager to see the first collisions of the LHC Run2. The recent news that the LHC restart may be delayed because of a hardware issue gives us extra time to prepare for those collisions. Far from being idle waiting for collisions, CMS is busy taking advantage of other types of collision.

    CMS is never idle. Without beams, the data-taking does not stop: collisions of cosmic particles high up in the atmosphere produce showers of particles, including muons. Some of these muons have high enough energies to penetrate through the 100 m of ground over the CMS detector and traverse it, leaving behind a trail of dots in our detectors. By connecting the dots, we can learn where the different detector components are inside the huge volume (~3700m3) of CMS to better than a millimetre. This is very important because the whole detector was taken apart and put back together in preparation for Run2. With the cosmic ray muons, we can also synchronise the different detectors down to one hundred-millionth of a second, given that cosmic muons interact with many detectors as they cross the experiment. After a long shutdown, we are also coming back to operating the experiment 24 hours a day, 7 days a week. There is always a shift crew operating and monitoring the experiment, an larger crew of experts that stand ready to intervene in case issues arise, and an even larger community that checks the quality of the data collected. So we exploit this cosmic debris to understand out detectors to the needed precision to later find again the Higgs boson and possibly new, as-yet undiscovered, particles; the more cosmic muon signals we record and analyse, the better prepared we will be to tackle proton collisions at 13 TeV.

    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
    CERN LHC Grand Tunnel

    LHC particles

    Quantum Diaries

     
  • richardmitnick 1:02 pm on March 26, 2015 Permalink | Reply
    Tags: , , J-PARC, , Particle Physics   

    From AAAS: “Shuttered Japanese proton accelerator nears restart” 

    AAAS

    AAAS

    25 March 2015
    Dennis Normile

    Idled after a radiation leak in May 2013, the Japan Proton Accelerator Research Complex (J-PARC) in Tokaimura took a step toward resuming full operations yesterday when the governor of Ibaraki Prefecture accepted a set of countermeasures aimed at preventing another accident. If the facility passes a final inspection by Japan’s Nuclear Regulation Authority, J-PARC could resume normal operations by the end of next month.

    Japan Proton Accelerator Research Complex J-PARC
    J-PARC

    It has been a long slog. An independent investigative panel convened by J-PARC concluded that the accident resulted from a combination of equipment malfunction and human error. In J-PARC’s Hadron Experimental Facility, a proton beam from a 50-GeV synchrotron strikes a target to produce a variety of secondary subatomic particles, including kaons, pions, and muons for use in experiments to determine their characteristics and interactions. On 23 May 2013, a malfunction sent a brief, unexpectedly high intensity beam at a gold target and vaporized radioactive material leaked into the experiment hall. Unaware of what had happened, researchers and staff inhaled contaminated air and also vented it outside the building. J-PARC took 34 hours to notify local and national authorities of the accident. All experiments were halted pending an investigation.

    The expert panel later determined that 34 people had inhaled the vapors and received slight internal radiation exposure that wasn’t deemed harmful and that the release outside the building posed no threat to area residents or the environment. Nonetheless, J-PARC, operated jointly by the High Energy Accelerator Research Organization and the Japan Atomic Energy Agency, then had to convince local and national authorities they could resume operating the facility without endangering staff or the community.

    The countermeasures developed over the past 2 years include upgrading schemes to minimize the impact of equipment glitches, making key experimental chambers airtight, fitting ventilation equipment with filters, and upgrading radiation monitoring and alarm systems. Researchers and staff have received safety training. Designated, trained emergency response personnel will be on hand at all times during operations and J-PARC will conduct accident drills several times annually.

    Experiments resumed at J-PARC’s Materials and Life Science Experimental Facility in February 2014 and at the Neutrino Experimental Facility last May after reviews and strengthening of safety programs.

    J-PARC Neutrino Experimental Facility
    J-PARC Neutrino Experimental Facility Tunnel
    J-PARC Neutrino Experimental Facility

    But more extensive work was needed in the hadron facility. The upgrades were accepted by the prefecture’s own panel of experts earlier this month. Yesterday’s presentation to the governor was largely symbolic. Starting next week, J-PARC officials will explain their strengthened safety measures at three public meetings in nearby towns. The final green light must come from the Nuclear Regulation Authority, which will inspect the facility next month.

    See the full article here.

    The American Association for the Advancement of Science is an international non-profit organization dedicated to advancing science for the benefit of all people.

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  • richardmitnick 2:29 pm on March 19, 2015 Permalink | Reply
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    From LC Newsline: “Updating the physics case for the ILC” 

    Linear Collider Collaboration header
    Linear Collider Collaboration

    19 March 2015

    3
    Hitoshi Yamamoto

    Director’s Corner

    1

    The physics case of the ILC has been studied intensively for many years, culminating in the physics volume of the Technical Design Report (TDR).

    ILC schematic
    ILC

    It was followed by efforts to compare various machines such as the European Strategy studies and the Snowmass studies. Still, the scientific and political environments surrounding the ILC keep changing. On the scientific front, the LHC has found the Higgs particle and placed limits on new physics.

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

    The LHC is now upgrading the energy and a new run is about to start. On the political side, the committees of the MEXT in Japan are evaluating the case for the ILC both technically and scientifically. It is thus important that we continue to update the physics case for the ILC and communicate it to relevant people.

    The task of updating the physics case for the ILC largely lies on the shoulders of the physics working group of the LCC. With the members of the MEXT committees as audience in mind, they have produced a document called Precis of the Physics Case for the ILC. This turned out to be an extremely useful document for newcomers such as incoming graduate students to learn about the physics of the ILC. It was, however, a little too technical for the audience originally intended. To fill the gap, it was followed by a shorter document intended really for general public – Scientific Motivations for the ILC. This latter document is now mostly ready for distribution. The content of these documents are used by members of those committees in their discussions.

    When evaluating the competitiveness of the ILC, we need to consider circular electron-positron colliders as well as a luminosity-upgraded LHC. At present, there are two studies on next-generation circular electron-positron collider: one at CERN and another in China. The one at CERN is called the FCC (Future Circular Collider) study the main part of which is a proton-proton collider with an optional electron-positron collider to start with. It would start after the LHC ends around 2035. The stated timing of the Chinese circular electron-positron collider, called CEPC, is earlier and about the same as that of the ILC. The CEPC is a Higgs factory with the design luminosity per collision point is about three times that of the baseline ILC running as a Higgs factory. It should be noted, however, that the upgraded ultimate ILC luminosity as a Higgs factory is four times that of the baseline. A merit of a circular collider is that multiple collisions points can be arranged. The CEPC would run with two collision points. All in all, the ILC
    as a Higgs factory is quite similar in luminosity to the CEPC. The wall plug power for the ultimate ILC Higgs factory is 187 MW, which is about the same as the current LHC, while that of CEPC is more than twice as much.

    2
    LC, LHC and the Chinese CEPC in overview

    At the latest LCB (Linear Collider Board) meeting, the way to communicate the physics case of the ILC to public was one of the topics intensively discussed. The LCB has then agreed that we need a short bulleted list of the physics case for the ILC. Several of us then sat down and came up with three points. Here they are with some editing:

    Important properties are the interaction strength between Higgs and other particles. ILC can measure them 3 to 10 times more accurately then the ultimate LHC. This means that the ILC is equivalent to 10 to 100 ultimate LHCs running simultaneously.

    The LHC can reach higher energy than the ILC, but can miss important phenomena.

    At the Tevatron collider, which is similar to the LHC, more than 10,000 Higgs particles were created but no clear signal was detected. At the ILC, about 100 Higgs particles are enough.

    FNAL Tevatron
    Fermilab CDF
    Fermilab DZero
    Tevatron at FNAL

    Circular electron-positron colliders have fundamental limits for energy increase due to synchrotron radiation.

    In the Standard Model of particle physics, the Higgs particle is the key particle and top quark is the heaviest particle.

    5
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    Higgs-Higgs, Higgs-top interactions cannot be directly measured at the circular electron colliders since they cannot reach high enough energy. When a new particle sits at just above the energy limit, the ILC could be upgraded to reach the energy by making it longer or using higher accelerating gradient while it is difficult for a circular collider.

    See the full article here.

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

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

    Linear Collider Colaboration Banner

     
  • richardmitnick 9:28 am on March 19, 2015 Permalink | Reply
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    From FNAL: “Physics in a Nutshell – Happy trails” 

    FNAL Home


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

    Thursday, March 19, 2015
    Jim Pivarski

    1
    This shows a particle identified in a photograph of a bubble chamber (left) and a computer reconstruction of signals from a silicon tracker (right).

    Much of the complexity of particle physics experiments can be boiled down to two basic types of detectors: trackers and calorimeters. They each have strengths and weaknesses, and most modern experiments use both. This and the next Physics in a Nutshell are about trackers and calorimeters, to kick off a series about detectors in general.

    The first tracker started out as an experiment to study clouds, not particles. In the early 1900s, Charles Wilson built an enclosed sphere of moist air to study cloud formation. Dust particles were known to seed cloud formation — water vapor condenses on the dust to make clouds of tiny droplets. But no matter how clean Wilson made his chamber, clouds still formed.

    Moreover, they formed in streaks, especially near radioactive sources. It turned out that subatomic particles were ionizing the air, and droplets condensed along these trails like dew on a spider web.

    This cloud chamber was phenomenally useful to particle physicists — finally, they could see what they were doing! It’s much easier to find strange, new particles when you have photos of them acting strangely. In some cases, they were caught in the act of decaying — the kaon was discovered as a V-shaped intersection of two pion tracks, since kaons decay into pairs of pions in flight.

    In addition to turning vapor into droplets, ionization trails can cause bubbles to form in a near-boiling liquid. Bubble chambers could be made much larger than cloud chambers, and they produced clear, crisp tracks in photographs. Spark chambers used electric discharges along the ionization trails to collect data digitally. More recently, time projection chambers measure the drift time of ions between the track and a high-voltage plate for more spatial precision, and silicon detectors achieve even higher resolution by collecting ions on microscopic wires printed on silicon microchips. Today, trackers can reconstruct millions of three-dimensional images per second.

    The disadvantage of tracking is that neutral particles do not produce ionization trails and hence are invisible. The kaon that decays into two pions is neutral, so you only see the pions. Neutral particles that never or rarely decay are even more of a nuisance. Fortunately, calorimeters fill in this gap, since they are sensitive to any particle that interacts with matter.

    Interestingly, the Higgs boson was discovered in two decay modes at once. One of these, Higgs to four muons, uses tracking exclusively, since the muons are all charged and deposit minimal energy in a calorimeter. The other, Higgs to two (neutral) photons, uses calorimetry exclusively, which will be the subject of the next Nutshell.

    See the full article here.

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    Fermilab Campus

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

     
  • richardmitnick 12:28 pm on March 17, 2015 Permalink | Reply
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    From Symmetry: “Experiments combine to find mass of Higgs” 

    Symmetry

    March 17, 2015
    Sarah Charley

    1
    Illustration by Thomas McCauley and Lucas Taylor, CERN

    The CMS and ATLAS experiments at the Large Hadron Collider joined forces to make the most precise measurement of the mass of the Higgs boson yet.

    CERN CMS New II
    CMS

    CERN ATLAS New
    ATLAS

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles
    LHC

    On the dawn of the Large Hadron Collider restart, the CMS and ATLAS collaborations are still gleaning valuable information from the accelerator’s first run. Today, they presented the most precise measurement to date of the Higgs boson’s mass.

    “This combined measurement will likely be the most precise measurement of the Higgs boson’s mass for at least one year,” says CMS scientist Marco Pieri of the University of California, San Diego, co-coordinator of the LHC Higgs combination group. “We will need to wait several months to get enough data from Run II to even start performing any similar analyses.”

    The mass is the only property of the Higgs boson not predicted by the Standard Model of particle physics—the theoretical framework that describes the interactions of all known particles and forces in the universe.

    3
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    The mass of subatomic particles is measured in GeV, or giga-electronvolts. (A proton weighs about 1 GeV.) The CMS and ATLAS experiments measured the mass of the Higgs to be 125.09 GeV ± 0.24. This new result narrows in on the Higgs mass with more than 20 percent better precision than any previous measurements.

    Experiments at the LHC measure the Higgs by studying the particles into which it decays. This measurement used decays into two photons or four electrons or muons. The scientists used data collected from about 4000 trillion proton-proton collisions.

    By precisely pinning down the Higgs mass, scientists can accurately calculate its other properties—such as how often it decays into different types of particles. By comparing these calculations with experimental measurements, physicists can learn more about the Higgs boson and look for deviations from the theory—which could provide a window to new physics.

    “This is the first combined publication that will be submitted by the ATLAS and CMS collaborations, and there will be more in the future,” says deputy head of the ATLAS experiment Beate Heinemann, a physicist from the University of California, Berkeley, and Lawrence Berkeley National Laboratory.

    ATLAS and CMS are the two biggest Large Hadron Collider experiments and designed to measure the properties of particles like the Higgs boson and perform general searches for new physics. Their similar function allows them to cross check and verify experimental results, but it also inspires a friendly competition between the two collaborations.

    “It’s good to have competition,” Pieri says. “Competition pushes people to do better. We work faster and more efficiently because we always like to be first and have better results.”

    Normally, the two experiments maintain independence from one another to guarantee their results are not biased or influenced by the other. But with these types of precision measurements, working together and performing combined analyses has the benefit of strengthening both experiments’ results.

    “CMS and ATLAS use different detector technologies and different detailed analyses to determine the Higgs mass,” says ATLAS spokesperson Dave Charlton of the University of Birmingham. “The measurements made by the experiments are quite consistent, and we have learnt a lot by working together, which stands us in good stead for further combinations.”

    It also provided the unique opportunity for the physicists to branch out from their normal working group and learn what life is like on the other experiment.

    “I really enjoyed working with the ATLAS collaboration,” Pieri says. “We normally always interact with the same people, so it was a real pleasure to get to know better the scientists working across the building from us.”

    With this groundwork for cross-experimental collaboration laid and with the LHC restart on the horizon, physicists from both collaborations look forward to working together to increase their experimental sensitivity. This will enable them not only to make more precise measurements in the future, but also to look beyond the Standard Model into the unknown.

    See the full article here.

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    Symmetry is a joint Fermilab/SLAC publication.


     
  • richardmitnick 5:35 am on March 17, 2015 Permalink | Reply
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    From New Scientist: “Quark stars: How can a supernova explode twice?” 2013 But Well Worth the Read 

    NewScientist

    New Scientist

    09 December 2013
    Anil Ananthaswamy

    What do you get when you melt a neutron star? An unimaginably dense lump of strange matter and a whole new celestial beast

    1
    (Image: Matt Murphy)

    ON 22 September last year, the website of The Astronomer’s Telegram alerted researchers to a supernova explosion in a spiral galaxy about 84 million light years away. There was just one problem. The same object, SN 2009ip, had blown up in a similarly spectacular fashion just weeks earlier. Such stars shouldn’t go supernova twice, let alone in quick succession. The thing was, it wasn’t the only one, the next year another supernova, SN 2010mc, did the same.

    One of the few people not to be bamboozled was Rachid Ouyed. “When I looked at those explosions, they were talking to me right away,” he says. Ouyed, an astrophysicist at the University of Calgary in Alberta, Canada, thinks that these double explosions are not the signature of a supernova, but something stranger. They may mark the violent birth of a quark star, a cosmic oddity that has only existed so far in the imaginations and equations of a few physicists. If so they would be the strongest hints yet that these celestial creatures exist in the cosmic wild.

    The implications would be enormous. These stars would take pride of place alongside the other heavenly heavyweights: neutron stars and black holes. They could help solve some puzzling mysteries related to gamma-ray bursts [GRBs] and the formation of the heftiest elements in the universe. Back on Earth, quark stars would help us better understand the fundamental building blocks of matter in ways that even machines like the Large Hadron Collider cannot.

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

    Astrophysicists can thank string theorist Edward Witten for quark stars. In 1984, he hypothesised that protons and neutrons may not be the most stable forms of matter.

    Both are made of two types of smaller entities, known as quarks: protons are comprised of two “up” quarks and one “down” quark, whereas neutrons are made of two downs and one up. Up and down are the lightest of six distinct “flavours” of quark. Add the third lightest to the mix and you get something called strange quark matter. Witten argued that this kind of matter may have lower net energy and hence be more stable than nuclear matter made of protons and neutrons.

    Quark nova

    If so, we might all start decaying into strange matter. But don’t fret. You either need to wait around longer than the age of the universe for the stuff to form spontaneously, or find somewhere with the right conditions to start the process. One place this could happen is inside neutron stars, the dense remnants of certain types of supernovae.

    When a star many times more massive than the sun runs out of fuel, its inner core implodes. The outer layers are cast off in a spectacular explosion. What’s left behind is a rapidly spinning neutron star, which as the name implies is made mainly of neutrons, with a crust of iron. Whirling up to 1000 times per second, a neutron star is constantly shedding magnetic fields. Over time, this loss of energy causes the star to spin slower and slower. As it spins down, the centrifugal forces that kept gravity at bay start weakening, allowing gravity to squish the star still further.

    In what is a blink of an eye in cosmic time, the neutrons can be converted to strange quark matter, which is a soup of up, down and strange quarks. In theory, this unusual change happens when the density inside the neutron star starts increasing. New particles called hyperons begin forming that contain at least one strange quark bound to others.

    However, the appearance of hyperons marks the beginning of the end of the neutron star. “Once you start to form hyperons, then you can start the nucleation of the first droplet of strange quark matter,” says Giuseppe Pagliara of the University of Ferrara in Italy. As the density in the core continues to increase, the star’s innards “melt”, freeing quarks from their bound state. In fact, a single droplet of strange matter is enough to trigger a runaway process that converts all the neutrons. What was a neutron star turns into a quark star.

    Of course, this assumes that Witten is correct about strange quark matter being more stable than neutrons. No one has yet proved him wrong, but it is a tough idea for some to swallow. “More conservative thinkers are just not open to the idea that free quarks exist in neutron stars,” says Fridolin Weber, an astrophysicist at the San Diego State University in California.

    Not so the daring ones. Ouyed, for instance, has been trying to convince his fellow astrophysicists of the existence of quark stars for more than a decade. Not only do these intrepid few think that quarks can exist freely inside neutron stars, they have even thought about what comes next. “We all agree that if quark stars exist, then the conversion of normal, ordinary matter into a quark star will be a very exothermic process, a lot of energy will be released,” says Pagliara. “How this energy is released is a matter of debate.”

    On one hand, Pagliara and his colleagues have done extensive simulations to show that this conversion will happen in a matter of milliseconds. In what he calls a “strong deflagration”, the neutron star burns up as it turns into a quark star. There is no explosion.

    Ouyed, on the other hand, begs to differ. His team’s simulations show that the conversion is most likely to be an extremely violent process. The seed of strange quark matter spreads until it reaches the outer crust of the neutron star. As the part of the star that has been turned into quark matter separates from the iron-rich crust, it collapses. The collapse halts when the inner core becomes incredibly dense and rebounds, creating a shock wave. Much as in a supernova, the iron-rich crust and leftover neutrons are ejected in another spectacular explosion – a “quark nova”.

    Hurtling through space, the quark nova ejecta then slam into the earlier supernova remnants, causing them to light up again, as they did after the explosion of the original, conventional star. What’s left behind is a quark star. “It was very hard to find solutions where the entire neutron star turned into a quark star, in just a puff with no explosion,” says Ouyed.

    Double explosion

    Depending on the mass of the star before its first explosion, the second blast could occur anywhere from seconds to years after the original supernova. Too soon, and the two explosions would merge, appearing as one blast, smeared out in time. Too late, and the supernova ejecta would have dispersed long before the detonation of the quark nova, and there would be no re-brightening.

    But if the timing is just right, the outcome should be observable. In 2009, Ouyed’s team predicted that if the quark nova goes off days or weeks after the supernova, there should be two peaks in energy: the first being the supernova explosion itself, and the second being the reheating of the supernova ejecta. The objects SN 2009ip and SN 2010mc matched predictions in ways almost too good to be true.

    SN 2009ip had its first major explosion in early August 2012, and 40 days later flared up again. SN 2010mc was eerily similar in its outbursts, showing a double explosion in which the peaks were about 40 days apart. While other researchers continue trying to explain these unusual observations using their tried-and-tested models of supernovae, Ouyed is convinced that we have witnessed quark stars being born.

    Oddly, it is the first peak in both events that convinces him. If these have all the characteristics of a regular supernova, it makes the second boom harder to explain using conventional arguments. “When you look at the first ejecta, it looks like a duck and walks like a duck: it’s a supernova,” says Ouyed. “Then what’s the second one?”

    He points the finger at quark novae. “We just applied our model of the dual shock quark nova, and it was actually easy to fit,” he says. “That’s the beauty of it.”

    While Pagliara and Ouyed’s teams disagree on whether the transition from a neutron star to a quark star is explosive, they do agree that space should be littered with quark stars. How should we look for them?

    We might be mistaking some of them for neutron stars, says Pagliara. Most neutron stars weigh as much as 1.4 suns or slightly more. The best studied examples, orbiting each other in systems called Hulse-Taylor binary pulsars, certainly follow this pattern. Both neutron stars involved weigh in at 1.4 solar masses. However, Pagliara is bothered by two discoveries of neutron stars that tip the scales at 2 solar masses each. “It’s difficult to reach this mass with normal particle components like neutrons, protons and hyperons,” he says.

    This has to do with a property of matter called its equation of state. Equations of state describe how matter behaves under changes in physical conditions, such as pressure and temperature. Hyperons, which are precursors to strange quark matter, have a “soft” equation of state. Their existence in the dense core of a neutron star makes the star more compressible, causing it to shrink in size.

    Astronomers estimate that neutron stars are about 10 kilometres across – but squeezing 2 solar masses into an object of such size would end up creating a black hole. Pagliara says that compact stars weighing 2 solar masses or more have to be bigger, or put another way, the matter has to be “stiffer” so that gravity cannot compress it as much. There is one candidate with a stiffer equation of state: strange quark matter.

    Pagliara and his colleague Alessandro Drago and others claim that the compact stars we have spotted come from two families. The smaller ones must be the run-of-the-mill neutron stars. The larger ones must be quark stars. The only way to verify this claim is to measure their masses and also measure their radii to the nearest kilometre. A proposed European satellite mission called the Large Observatory for X-ray Timing could do just that. Its aim is to measure the equation of state for compact objects – and thus differentiate between neutron stars and quark stars.

    ESA LOFT
    ESA/LOFT

    Meanwhile, Ouyed’s team is concentrating on predictions based on their quark nova model. One prediction has to do with the creation of heavy elements in the universe. Once a massive star goes supernova, weighty elements are synthesised in a matter of milliseconds, when neutrons are absorbed into iron nuclei. These neutron-rich nuclei are unstable and decay into elements further up in the periodic table when neutrons get converted to protons. “But the challenge with supernovae has always been to go to really heavy elements,” says Ouyed. The iron and neutrons needed for the process are in short supply because most of them are left behind in the remnant neutron star.

    The quark nova solves that problem. Its ejecta are a potent mix of neutrons and iron from the neutron star’s crust, providing just the laboratory for synthesising the heaviest elements. Ouyed is urging astronomers to study double explosions carefully. His team predicts that the second blast should show the presence of elements heavier than atomic mass 130, elements which should be missing from the first explosion.

    The conversion of a neutron star to a quark star could also solve another problem plaguing astrophysics: the source of some long-duration gamma-ray bursts, which are among the brightest events in the universe. On 9 July 2011, NASA’s SWIFT gamma-ray satellite saw a burst with two spectacular peaks of emission, spaced 11 minutes apart.

    NASA SWIFT Telescope
    NASA/Swift

    And the second was the stronger of the two. The traditional “collapsar” model of gamma-ray bursts relies on a star collapsing to a black hole. As the last remnants of the doomed star fall in, it is thought to result in such an emission. But 11 minutes is an eternity for a black hole – it’s hard to make sense of the second peak.

    Pagliara thinks his team has the answer. According to their model, a neutron star converts to a quark star without an explosion. Yet there is still a tremendous release of energy, which Pagliara suspects goes into gamma rays. This could explain the second peak. “At the moment, and it’s speculation, we think that this second event could be related to quark stars,” he says. “If you want to see a possible signature of formation of quark matter, you should probably look at those gamma-ray bursts that have an activity long after the main event.”

    Quark world

    Confirming the existence of quark stars and verifying their properties could have a huge impact on particle physics. Colliders like the LHC and the Relativistic Heavy Ion Collider (RHIC) in Brookhaven National Laboratory [BNL]in New York have been smashing heavy ions head-on to create a state of matter called a quark-gluon plasma, where quarks are essentially free.

    BNL RHIC Campus
    BNL RHIC
    RHIC at BNL

    The best way to study this phase of matter is using a method called lattice quantum chromodynamics [QCD]. But physicists have only been able to solve the equations of lattice QCD for high temperatures and low density – the conditions created at the LHC and the RHIC. The equations are intractable for other conditions. For instance, it is impossible to calculate the density at which protons and neutrons can melt into their constituent quarks at low temperatures.

    Enter quark stars. First, if their existence is confirmed, it proves that quarks can exist freely at high densities and low temperatures, rather than bound up in hadrons – the catch-all name given to any particle made of quarks. Second, for the explosive quark nova model Ouyed’s team has shown that the density at which quarks get freed is intimately linked to the time lag between the supernova and the quark nova. Measure the timing of the double explosion and you will glean important clues about conditions at the transition. “The quark nova is a very beautiful bridge that straddles the hadronic world and the quark world,” says Ouyed. “It’d be a very nice tool to use for physics and astrophysics.”

    Weber agrees that quark stars, if they exist, would be a unique astrophysical laboratory. They would help us probe properties of matter in ways that we cannot do with the best colliders on Earth – in the domain of high densities and low temperatures. “This is a regime that is only accessible to stars, and only stars can tell us what will happen.”

    See the full article here.

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  • richardmitnick 1:20 pm on March 12, 2015 Permalink | Reply
    Tags: , , , , , Particle Physics   

    From Don Lincoln at FNAL: The Detectors at the LHC 

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

    The Large Hadron Collider or LHC is the world’s biggest particle accelerator, but it can only get particles moving very quickly. To make measurements, scientists must employ particle detectors. There are four big detectors at the LHC: ALICE, ATLAS, CMS, and LHCb. In this video, Fermilab’s Dr. Don Lincoln introduces us to these detectors and gives us an idea of each one’s capabilities.

    CERN LHC Map
    CERN LHC Grand Tunnel
    CERN LHC particles

    CERN ALICE New II
    ALICE

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

    CERN LHCb New II
    LHCb

    See the full article here.

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    Fermilab Campus

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

     
  • richardmitnick 10:25 am on March 12, 2015 Permalink | Reply
    Tags: , , , , , Particle Physics   

    From FNAL- “Frontier Science Result: CDF and DZero Joining forces to test the Higgs boson’s spin and parity” 

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

    Thursday, March 12, 2015
    Tom Junk

    1
    This plot shows the observed and expected upper limits at the 95 percent credibility level on the fraction of exotic boson production for two cases (spin zero with negative parity and spin two with positive parity). A signal scale of one corresponds to the Standard Model.

    The Higgs boson caused a lot of excitement when the ATLAS and CMS collaborations announced its discovery in 2012.

    CERN ATLAS New
    ATLAS

    CERN CMS New
    CMS

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

    Everyone was bursting with questions: How much does it weigh? How is it made? How does it decay? Does it have any spin, and if so, how much? Does it look the same in a mirror or not (the question of “parity”)?

    The Standard Model predicts the answers to all of these questions, although some depend on the Higgs boson mass, which ATLAS and CMS have measured precisely.

    2
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    So far, the new particle observed at the LHC is consistent with all of the Standard Model’s predictions. In particular, ATLAS and CMS’s measurements of the spin and parity allowed them to confidently identify the new particle as a Higgs boson.

    The Tevatron experiments, CDF and DZero, also found evidence for a Higgs boson in 2012, looking at events in which two bottom-flavored jets recoiled from a vector boson — either a Z or a W.

    FNALTevatron
    Tevatron

    FNAL CDF
    CDF

    FNAL DZero
    DZero

    All the same questions come up, as some models predict that one may observe a mixture of Higgs particles at the Tevatron different from what was observed at the LHC due to the different mixtures of production and decay modes that provide the most sensitivity.

    At the Tevatron, the Higgs boson’s properties were found to be consistent with those predicted for the Standard Model Higgs boson. Theorists provided a clever way to test some models of the Higgs boson’s spin and parity using Tevatron data: Higgs bosons with exotic spin and parity would be produced with more energy than the Standard Model version. CDF and DZero looked at the energies and angles of particles produced in Higgs boson events to check. But most events at the Tevatron are non-Higgs-boson background events, so a lot of hard work went in to test the models.

    Both DZero and CDF modified their Higgs boson analyses to search for the new particles, if they are present in addition to the Standard Model Higgs boson, or if they replace it entirely. Neither experiment found evidence for the exotic states, and the data prefer the Standard Model interpretation.

    But a much stronger statement can be made when CDF and DZero join forces and combine their results, using the same techniques used in the Standard Model Higgs search combinations. The signal strength of exotic Higgs bosons in the JP=0- and 2+ states is no more than 0.36 times that predicted for the Standard Model Higgs boson. Given a choice between the Standard Model Higgs boson, which has JP=0+, and one of the two exotic models replacing it with the same signal strength, the Tevatron data disfavors the exotic models with a significance of 5.0 standard deviations for 0- and 4.9 standard deviations for 2+.

    The figure above shows limits on the fraction of exotic Higgs boson production as functions of the total signal rate, assuming that the Higgs signal is a mixture of the Standard Model Higgs boson and one of the exotic kinds. The particle for which the Tevatron experiments reported evidence in 2012 is consistent with having the spin and parity predicted by the Standard Model.

    —Tom Junk

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

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    Fermilab Campus

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

     
  • richardmitnick 12:10 pm on March 3, 2015 Permalink | Reply
    Tags: , , , Particle Physics   

    From BBC: “New Higgs detection ‘closes circle’” 

    BBC
    BBC

    3 March 2015
    Jonathan Webb

    1
    The low energy work is separate from studies at the Large Hadron Collider

    Physicists who detected a version of the Higgs Boson in a superconductor say their discovery closes a “historical circuit”.

    They also stressed that the low-energy work was “completely separate” from the famous evidence gathered by the Large Hadron Collider.

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

    Superconductivity was the field of study where the idea for the Higgs originated in the 1960s. But the particle proved impossible to witness because it decays so fast. This new signature was glimpsed as very thin, chilled layers of metal compounds were pushed very close to the boundary of their superconducting state. This process creates a “mode” in the material that is analogous to the Higgs Boson but lasts much longer.

    Rather than the study of particles, it belongs in the field known condensed matter physics; it also uses much less energy than experiments at the LHC, where protons are smashed together at just under the speed of light. It was at the LHC in 2012 that the Higgs Boson, believed to give all the other subatomic particles their mass, was detected for the very first time.

    The new superconductor discovery was presented amid much discussion at this week’s March Meeting of the American Physical Society in San Antonio, Texas. It also appeared in the journal Nature Physics in January. Speaking at the meeting, Prof Aviad Frydman from Bar Ilan University in Israel responded in no uncertain terms to the suggestion that his work could substitute for the LHC. “That’s complete nonsense,” he told the BBC. “In fact it’s kind of embarrassing.”

    2
    The team used superconducting films made from compounds of niobium (pictured here as a fibre) and indium

    Prof Frydman said the convergence of results from “two extremes of physics” was the most striking aspect of his findings, which were the fruit of a collaboration spanning Israel, Germany, Russia, India and the USA. “You take the high energy physics, which works in gigaelectronvolts. And then you take superconductivity, which is low energy, low temperature, one millivolt. “You have 10 to the 15 (one quadrillion) orders of magnitude between them, and the same physics governs both! That is the nice thing.”

    “It’s not that our experiment can replace the LHC. It’s completely separate.”

    Superconductors are materials that, when under critical conditions including temperatures near absolute zero (-273C), allow electrons to move with complete freedom. It was attempts to understand this property that ultimately led to Peter Higgs and others proposing the now-famous boson. “In the 1960s there were two distinct, basic problems. One was superconductivity and one was the mass of particles,” Prof Frydman explained.

    “People like Phil Anderson developed this mechanism for understanding superconductivity. And the guys from high energy saw this kind of solution, and applied it to high energy physics. That’s where the Higgs actually came from.” So the detection of a superconducting Higgs, he added, is “closing a historical circuit”. This closure was a long time coming. Detecting the Higgs in a superconductor had seemed almost impossible. This was because the energy required to excite (and detect) the Higgs mode – even though vastly less than that needed to generate its analogous particle inside the LHC – would destroy the very property of superconductivity. The Higgs mode would vanish almost before it arose. But when Prof Frydman and his colleagues held their thin films in conditions very close to the “critical transition” between being a superconductor and an insulator, they created a longer-lived, lower-energy Higgs mode.

    Other claims of a superconducting Higgs have been made in the past, including one in 2014. They have all faced criticism. Indeed, Prof Frydman’s conference presentation was also greeted with intense questions from others in the field. “Like any physical finding, there are different interpretations,” he said. “The Cern experiment is also being contested.”

    See the full article here.

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  • richardmitnick 10:52 am on February 19, 2015 Permalink | Reply
    Tags: , , , Particle Physics   

    From FNAL: “Physics in a Nutshell How many forces?” 

    FNAL Home


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

    Thursday, Feb. 19, 2015
    FNAL Don Lincoln
    Don Lincoln

    1
    Unlike in Star Wars, where there was but one force with a light and dark side, the number of fundamental forces is a much murkier question.

    If you’ve read many of my columns, you know quite a bit about the Standard Model.

    3
    The Standard Model of elementary particles (more complete depiction), including the Higgs boson, the three generations of matter fields, and the gauge bosons, as well as their properties and interactions, and the effect of spontaneous electroweak symmetry breaking by the Higgs field.

    You know that there are quarks and leptons. You’ve heard about the gluon, the W and Z bosons, the photon and the graviton. And you know that this means that there are four fundamental forces: the strong and weak nuclear forces, electromagnetism, and gravity. Easy peasy.

    However, the reality is actually a lot murkier: Not all forces are independent. For instance, back in the 1830s, scientists knew of two distinct forces: electricity and magnetism. But when Maxwell wrote down his equations for electric and magnetic forces in the 1860s, it became clear that the two were really one force, electromagnetism.

    Similarly, in the late 1960s, physicists mathematically unified the electromagnetic and weak forces and showed that there was just one electroweak force. Under this reasoning, there are only three forces in nature: strong, electroweak and gravity.

    But then the Higgs boson was discovered in 2012, indicating yet another force, specifically the Higgs force. So now we’re back up to four. On the other hand, the Higgs mechanism is the phenomenon that makes the weak force and electromagnetism appear to be different. So maybe it’s tied in with the electroweak force. That statement is as much speculation as theory, but it would bring the number of fundamental forces back down to three.

    And then there is the hope of physicists to unify the electroweak force and the strong force into a single grand unified theory, or GUT. This would reduce the force count to two: the electroweak-strong-Higgs force and the gravitational force. We physicists are an ambitious lot, and we eventually hope to invent a theory of everything or TOE, which would unify GUT and gravity. This would leave us with but a single force, and the apparent fundamental forces would just be different manifestations of the one primordial force.

    So where does that leave us? Well, it’s probably safe to talk of five fundamental forces (strong, weak, electromagnetism, gravity and Higgs) and probably more accurate to speak of four (strong, electroweak, gravity and Higgs). But physicists are constantly trying to figure out the fundamental rules of the universe, and perhaps we are just a clever thought or two away from reducing that count further.

    The bottom line is that giving a number requires that you know what you are doing and what assumptions you are making. Physics, like all science, is a fluid endeavor and changes as our understanding improves. It’s not the number that matters, but rather knowing what the number means. Unless we’re talking lottery numbers. Then you better get it right.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

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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.

     
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