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  • richardmitnick 7:33 pm on September 21, 2014 Permalink | Reply
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    From BBC: “‘Artificial retina’ could detect sub-atomic particles” 

    BBC

    18 September 2014
    Melissa Hogenboom

    The human eye has inspired physicists to create a processor that can analyse sub-atomic particle collisions 400 times faster than currently possible.

    In these collisions, protons – ordinary matter – are smashed together at close to light speeds.

    pro
    The quark structure of the proton. The color assignment of individual quarks is arbitrary, but all three colors must be present. Forces between quarks are mediated by gluons

    These powerful smash-ups could yield new particles and help scientists understand matter’s mirror, antimatter.

    anti
    The quark structure of the antiproton

    The experimental processor could speed up the analysis of data from the collisions.

    Published in the pre-print arXiv server, the algorithm has been proposed for possible use in Large Hadron Collider (LHC) experiments at Cern in 2020. It could also be useful in any field where fast, efficient pattern recognition capabilities are needed.

    CERN LHC Grand Tunnel
    LHC

    The processor works in a similar way to the retina’s incredible ability to recognise patterns extremely quickly.
    Snapshots in time

    That is, individual neurons in our retinas are specialised to respond to particular shapes or orientations, which they do automatically before our brain is even consciously aware of what we are processing.

    pd
    Image of particle decay LHC machines produce 40 million collisions per second

    Cern physicist Diego Tonelli, one of a team of collaborators of the work, explained that the “artificial retina” detects a snapshot of the trajectory of each collision which is then immediately analysed.

    These snapshots are then mapped into an algorithm that can run on a computer, automatically scanning and analysing the charged particle trajectories, or tracks. Exposing the detector to future collisions will then allow teams sift out the interesting events.

    Data crunching

    Speed is of the essence here. There are roughly 40 million collisions per second and each can result in hundreds of charged particles.

    The scientists then have to plough through an incredible amount of data. It’s spotting the deviations from the norm that may give hints of new physics.

    lhcb
    LHCb experiment
    The LHC will be switched on again in early 2015

    An algorithm like this could therefore provide a useful way of crunching through this vast amount of data, in real time.

    “It’s 400 times faster than anything existing or foreseen for high energy physics applications. If implemented in a real experiment it will allow us to collect more interesting data more quickly,” Dr Tonelli told the BBC.

    Flavour physics

    The LHC has been switched off since February 2013 but is due to begin its hunt for new physics in 2015 when the giant machine will once again begin smashing together protons.

    As this happens, they break down and free up a huge amounts of energy that forms many neutral and charged particles. It’s the trajectories of the charged ones that can be observed.

    col
    Particle collisions
    A collision in the Large Hadron Collider creates tracks of charged particles

    The new algorithm is not aimed at the type of physics used to find the famous Higgs boson, instead it’s intended to be used for “flavour physics” which deals with the interaction of the basic components of matter, the quarks.

    Commenting on the work, Tara Shears a Cern particle physicist from the University of Liverpool, said it could be extremely useful to automatically “give us most information about what we want to study – Higgs, dark matter, antimatter and so on. The artificial retina algorithm looks like it does this brilliantly”.

    “When our detectors take these snapshots of the collisions – to us that’s like the picture that your eye sees and when your brain is scanning that picture and making sense of it, well we try and codify those rules into an algorithm that we run on computers that do the job for us automatically,” Prof Shears told the BBC’s Inside Science programme.

    “When the LHC continues… we will start to operate with a more intense beam of protons getting a much higher data rate, and then this problem of sifting out what you really want to study becomes really really pressing,” she added.

    “This artificial retinal algorithm is one of the latest steps in our mission to [understand the Universe], and it’s really good, it does the job vast banks of computers normally do.”

    The algorithm has been developed with the 2020 upgrade of the LHC in mind, which will have even more powerful collisions.

    See the full article here.

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  • richardmitnick 2:25 pm on June 6, 2014 Permalink | Reply
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    From Symmetry: “LHCb glimpses possible sign of new physics” 

    Symmetry

    June 06, 2014
    Sarah Charley

    This week at the LHC Physics conference in New York City, the LHCb collaboration presented a result that could be a hint of new physics.

    CERN LHCb New
    LHCb at CERN

    LHCb, one of the four largest experiments at the Large Hadron Collider, is run by scientists from more than 50 institutions worldwide, including four universities in the United States. It examines the properties of certain particles to look for deviations from the Standard Model of particle physics.

    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.

    The Standard Model predicts that electrons, muons and taus—all members of the lepton particle family—should behave in the same way and be produced in equal amounts in particle decays.

    “The Standard Model doesn’t distinguish between muons and electrons in these decays,” says Tom Blake, a Royal Society University Research Fellow working on this analysis. “As far as our equations are concerned, they are the same particle, so we should see them produced in near equal amounts.”

    In a result announced this week, LHCb scientists revealed that they have seen a hint that particles defy this Standard Model prediction. This could be caused by interference from undiscovered particles or forces.

    LHCb scientists saw the difference in decays of particles containing b-quarks. Typically, these particles decay to light hadrons shortly after they are produced. But in very rare instances, they create two leptons and a hadron instead.

    According to the Standard Model, this type of decay should have created an equal number of electrons and muons. Instead, they found that electrons were produced 25 percent of the time more often. If data collected in the next run of the LHC continues to support this result, it could be a sign of physics beyond the Standard Model.

    “If we continue to see this discrepancy, it could be evidence of a new particle—like a heavier cousin of the Z boson—interfering with the muon production,” says Michel De Cian, a postdoc at the University of Heidelberg, who presented the result.

    Previously, the Belle collaboration in Japan and the BaBar collaboration at SLAC also measured the ratio of muons to electrons produced during this decay. Both Belle and Babar found that the ratio was one-to-one, but the statistical uncertainty was so great that neither experiment was able to draw solid conclusions.

    The LHCb experiment does not yet have enough data to confirm or refute whether nature follows the Standard Model’s predictions either.

    “It’s interesting but inconclusive,” De Cian says. “We don’t have a large enough statistical significance to make any claims yet.”

    De Cian and Blake both hope that the next run of the LHC will provide more data and will help them shed light on the dark cracks and corners of the Standard Model.

    See the full article here.

    Symmetry is a joint Fermilab/SLAC publication.



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  • richardmitnick 7:17 am on May 10, 2014 Permalink | Reply
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    From LHCb at CERN: “Polarisation confirmed” 

    CERN New Masthead

    CERN LHCb New
    LHCb

    2014-05-09
    Anaïs Schaeffer

    The polarisation of photons emitted in the decay of a bottom quark into a strange quark, as predicted by the Standard Model, has just been observed for the first time by the LHCb collaboration. More detailed research is still required to determine the value of this polarisation with precision.

    event
    In this LHCb event, K, π and γ are emitted from a B+ → K+π-π+γ decay. This was investigated by the LHCb collaboration in order to study the photon (γ) polarisation.

    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.

    In this LHCb event, K, π and γ are emitted from a B+ → K+π-π+γ decay. This was investigated by the LHCb collaboration in order to study the photon (γ) polarisation.

    If we imagine that photons are like little spinning tops which spin around an axis aligned with their direction of propagation, we can identify two types of photons. Those that are “right-handed” turn in the same direction as a corkscrew, and those that are “left-handed” turn in the opposite direction. If for a large number of decays of a given type we can observe an imbalance between the production of right-handed photons and the production of left-handed protons, we can say that there is a polarisation.

    At CERN, the LHCb collaboration has been looking at precisely this phenomenon. In particular it has been studying the polarisation of the photon (γ) emitted in the decay of a bottom quark (b) into a strange quark (s): b → sγ. According to the predictions of the Standard Model of particle physics, the photons emitted in this decay should almost always be left-handed. But until now, this polarisation had not been demonstrated in an experiment. “Thanks to the data gathered by LHCb in 2011 and 2012, we have been able to study around 14,000 b → sγ decays,” explains Olivier Schneider, a physicist at EPFL and a member of the LHCb collaboration. “By counting the number of photons emitted in different directions, we have successfully demonstrated polarisation (see box). Further research is needed to determine if this is polarisation with an excess of left-handed photons, as predicted by the Standard Model, or an excess of right-handed photons, and in what proportions.”

    If the polarisation turns out to be different from the Standard Model prediction, where almost 100% left-handed photons are expected, it could mean a U-turn for particle physics: “If our research eventually shows a right-handed polarisation, or even just a left-handed polarisation different to that predicted by the Standard Model, it would open the door to new physics,” enthuses Olivier Schneider. “In fact, various theories beyond the Standard Model predict other polarisation values for the b → sγ transition. If these predictions were confirmed, it would open up a whole new front for particle physics.” Something which would be music to the ears of many physicists.

    Want to know more?

    fig 1
    Figure 1: the light blue plane is defined by the momenta of the K+, π- and π+ particles. By comparing the number of photons detected above (up) and below (down) this plane, physicists can calculate the Aud asymmetry, which is proportional to the photon polarisation.

    To be more precise, the LHCb collaboration investigated the B+ → K+π-π+γ decay, in which the b → sγ transition takes place. The imbalance between right-handed photons and left-handed photons can be revealed by the “up-down asymmetry (Aud)”, which was measured by comparing the number of photons detected above (up) and below (down) the plane defined by the K+, π- and π+ momenta in the rest frame of these three particles (see Figure 1).

    The Aud asymmetry was calculated for four mass intervals of the Kππ system: between 1100 and 1300 MeV/c2; between 1300 and 1400 MeV/c2; between 1400 and 1600 MeV/c2; and between 1600 and 1900 MeV/c2. These four Aud measurements are globally incompatible with the zero value, with a statistical significance of 5.2 sigma (see Figure 2), which indicates that the photons are indeed polarised.

    fig 2
    Figure 2: measurements of the Aud asymmetry for four mass intervals of the Kππ system.
    Note that the Aud asymmetry does not directly provide the λ polarisation value, but is proportional to it according to the relationship: Aud = k * λ, where k is a constant that is in principle different for each mass interval of the Kππ system. A more detailed study could allow the value of k to be determined for each mass of the Kππ system. This would also allow the polarisation to be calculated.

    See the full article here.

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  • richardmitnick 7:17 pm on April 9, 2014 Permalink | Reply
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    From CERN: “LHCb confirms existence of exotic hadrons” 

    CERN New Masthead

    9 Apr 2014
    Cian O’Luanaigh

    The Large Hadron Collider beauty (LHCb) collaboration today announced results that confirm the existence of exotic hadrons – a type of matter that cannot be classified within the traditional quark model.

    Hadrons are subatomic particles that can take part in the strong interaction – the force that binds protons inside the nuclei of atoms. Physicists have theorized since the 1960s, and ample experimental evidence since has confirmed, that hadrons are made up of quarks and antiquarks that determine their properties. A subset of hadrons, called mesons, is formed from quark-antiquark pairs, while the rest – baryons – are made up of three quarks.

    But since it was first proposed physicists have found several particles that do not fit into this model of hadron structure. Now the LHCb collaboration has published an unambiguous observation of an exotic particle – the Z(4430) – that does not fit the quark model.

    lhcb
    A view of the LHCb experiment at underground Point 8 on the Large Hadron Collider (LHC). The prominent tube is the LHC beam pipe, in which protons circulate at close to the speed of light (Image: Anna Pantelia/CERN)

    The Belle Collaboration reported the first evidence for the Z(4430) in 2008. They found a tantalizing peak in the mass distribution of particles that result from the decays of B mesons. Belle later confirmed the existence of the Z(4430) with a significance of 5.2 sigma on the scale that particle physicists use to describe the certainty of a result.

    LHCb reports a more detailed measurement of the Z(4430) that confirms that it is unambiguously a particle, and a long-sought exotic hadron at that. They analysed more than 25,000 decays of B mesons selected from data from 180 trillion (180 ×1012) proton-proton collisions in the Large Hadron Collider.

    “The significance of the Z (4430) signal is overwhelming – at least 13.9 sigma* – confirming the existence of this state,” says LHCb spokesperson Pierluigi Campana. “The LHCb analysis establishes the resonant nature of the observed structure, proving that this is really a particle, and not some special feature of the data.”

    See the full article here.

    [*I did not realize that a sigma value could be this high, until I discovered this chart here.]

    chart
    Example of two sample populations with the same mean and different standard deviations. Red population has mean 100 and SD 10; blue population has mean 100 and SD 50

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  • richardmitnick 9:10 am on March 7, 2014 Permalink | Reply
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    From CERN Courier: “Charmonium produced in unusual topology sheds light on QCD” 

    CERN LHCb New

    CERN LHCb Original

    The LHCb collaboration has released updated measurements of central exclusive production of the J/ψ and ψ(2S) mesons (LHCb collaboration 2014).

    Central exclusive production is a class of reactions in which one or two particles are produced from a beam collision, but the colliding hadrons emerge intact. At the LHC this leads to an unusual and distinctive topology of low-multiplicity events contained in a small rapidity interval with large rapidity gaps on either side. J/ψ and ψ(2S) mesons are produced when a photon emitted from one proton interacts with a pomeron (a colourless combination of gluons) from the other. Measurements of the process can be used to test QCD predictions – to improve our understanding of the distribution of gluons inside the proton – and are also sensitive to saturation effects.

    graph
    Photoproduction cross-section

    LHCb’s ability to trigger on low-momentum particles and the low number of proton–proton interactions per beam crossing provide an ideal environment to study these processes with particularly low multiplicity. Using data collected in 2011, around 56,000 central exclusive J/ψ and 1500 ψ(2S) mesons have been identified by reconstructing their decays to pairs of muons. While non-resonant backgrounds are very small, the challenge in the analysis is to estimate the larger background that arises when J/ψ and ψ(2S) mesons are produced and one or both of the colliding protons dissociate. As LHCb is instrumented in the forward region mainly, this effect often cannot be detected directly. Instead the collaboration has developed methods to estimate the background rate from the portion of events that are detected.

    The measured cross-sections are compared to theoretical predictions, as well as to photoproduction measurements from the HERA electron–proton collider and from fixed-target experiments. Although these environments are quite different from collisions at the LHC, the underlying process is the same. In the former a photon is emitted from an incoming electron beam, while the latter use photon beams directly.

    The figure shows a model-dependent comparison of the LHCb results with those from the other types of experiment. It plots the photoproduction cross-section as a function of the photon–proton centre-of-mass energy (W). There is a two-fold ambiguity in converting LHCb’s proton–proton differential cross-section to a photoproduction cross-section, corresponding to the photon being either an emitter or a target. This is resolved using recent results from the H1 experiment at HERA (H1 collaboration 2013). The data in the figure show broad consistency over two orders of magnitude, but are in marginal agreement with a single power-law distribution expected from leading-order QCD. Better agreement is provided either at next-to-leading order QCD (Jones et al. 2013) or by including saturation effects (Gay Ducati et al. 2013).

    See the full article here.


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  • richardmitnick 11:27 pm on March 1, 2014 Permalink | Reply
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    From LHCb at CERN: “Welcome to the LHCb experiment” 

    CERN New Masthead

    CERN LHCb Original

    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

    Fourteen billion years ago, the Universe began with a bang. Crammed within an infinitely small space, energy coalesced to form equal quantities of matter and antimatter. But as the Universe cooled and expanded, its composition changed. Just one second after the Big Bang, antimatter had all but disappeared, leaving matter to form everything that we see around us — from the stars and galaxies, to the Earth and all life that it supports.

    chart
    LHCb delivered and recorded luminosity in 2012, +1.1/fb indicates recorded luminosity in 2010-2011. The number of proton-proton (pp) collisions visible at LHCb, as well as the numbers of cc and bb quark pair produced within LHCb acceptance in 2010-2012 are also shown.

    28 February 2014: First observation of photon polarisation in b→sγ transition.

    The LHCb Collaboration has submitted today for publication a paper reporting the first observation of photon polarisation in b→sγ transition. The full 3 fb-1 Run 1 data sample was used to obtain this result. The Collaboration has presented already the first evidence for the photon polarization in this process at the summer 2013 conferences using about 2/3 of the whole data sample, see the news of 19 July 2013 for an introduction.

    Photon polarization is the quantum mechanical description of the classical polarized sinusoidal plane electromagnetic wave. Individual photon can have either right or left circular polarization or a superposition of both, read more here.

    The beauty particles decay mainly into charm particles, less frequently into strange particles. About once in every 3000 decays into strange particles a photon is emitted. At the underlying quark level a beauty b quark turns into a strange quark s by emitting a photon γ. This famous b→sγ transition is considered as a very interesting process in which signs of new physics could show up. The first evidence for this process was obtained by the CLEO Collaboration in 1993 and since then it was intensively studied in many experiments. This decays occurs only rarely since it requires a quantum fluctuation where a pair of heavy particles (a top quark and a W boson) appear and then rapidly vanish. The interaction between these particles is such that the emitted photon is expected to be almost 100% (left-handed) polarized. However, since the “virtual” top and W particles are not seen in the detector, they could equally well be replaced by other even heavier particles that are predicted in various theories that go beyond the Standard Model. Such theories have been proposed to address important unresolved questions in particle physics, such as the origin of the imbalance between matter and antimatter seen in the Universe. These models generally predict different values for the photon polarisation, and therefore it is seen as one of the most important measurements that can be made with the latest generation of experiments.

    graphs
    Researchers from the LHCb experiment have now succeeded to observe a non-vanishing value of the polarisation for the first time with a significance of 5.2σ. The analysis is based on nearly 14000 B+→K+π- π+ γ decays, for which the distribution of the γ angle with respect to the normal to the plane defined by the kaon and two pion system is studied in four intervals of the K+π- π+ mass which are shown in the image. The two curves are fits to the data points, allowing photon polarisation (solid blue curve) or setting it to zero (dashed red curve).

    This investigation is conceptually similar to the historical Wu experiment that discovered parity violation by measuring the asymmetry of the direction of a particle emitted in a weak decay.

    See the full article here.

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  • richardmitnick 6:26 am on October 30, 2013 Permalink | Reply
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    From LHCb at CERN: “Welcome to the LHCb experiment” 

    CERN New Masthead

    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.

    LHCb

    Fourteen billion years ago, the Universe began with a bang. Crammed within an infinitely small space, energy coalesced to form equal quantities of matter and antimatter. But as the Universe cooled and expanded, its composition changed. Just one second after the Big Bang, antimatter had all but disappeared, leaving matter to form everything that we see around us — from the stars and galaxies, to the Earth and all life that it supports.

    chart
    LHCb delivered and recorded luminosity in 2012, +1.1/fb indicates recorded luminosity in 2010-2011. The number of proton-proton (pp) collisions visible at LHCb, as well as the numbers of cc and bb quark pair produced within LHCb acceptance in 2010-2012 are also shown.

    See the full article here.

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  • richardmitnick 7:28 am on August 9, 2013 Permalink | Reply
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    From CERN: “Tracking new physics—horse or zebra?” 

    CERN New Masthead

    9 Aug 2013
    Ashley Jeanne Wennersherron

    If you hear hoof beats, common sense says the cause is more than likely a horse. Yet, the possibility still exists that you’re actually hearing a zebra. Physicists at LHCb are applying that same logic to an unusual finding in a recent analysis of the B meson.

    lhcb
    A view of the LHCb detector. (Image: Maximilien Brice/CERN)

    Around one in every million B mesons decays into an excited kaon and two muons. The decay can occur in several different ways, so physicists classify them in what they call bins. The Standard Model predicts precisely the probability of the angles of these particle decays in each bin. The experiment can measure this probability, so it is an observable. Any difference between the measured observable and prediction could indicate new physics.

    Nicola Serra of LHCb, one of the analysts of the B meson decay data from 2011, and his colleagues found such a difference.

    “Most of the observables we measured in this analysis were close to Standard Model expectations, but a particular observable showed a sizable discrepancy,” he says.

    On the ‘sigma’ scale that physicists use to describe the certainty of a result, Serra’s discrepancy between the expected and the measured result scored 3.7 sigma – there could be evidence for new physics but they need more data to confirm it. When they considered the probability of seeing that particular deviation with all of the data from the entire analysis, the sigma level dropped to 2.8 sigma, translating to a half a percent chance that the discrepancy is caused by statistical fluctuation. (The gold standard for a discovery is 5 sigma.)

    A team of theorists then looked at the same decay and included more observables than the LHCb group did. They found, with this aggregation of many measurements, a consistent pattern of deviations that boosted the sigma to 4.5. That’s almost to the level of discovery, but within parameters that measure the presence of possible new physics. These parameters are more inclusive than those the LHCb team used.

    ‘The theoretical interpretation is very interesting; that can’t be denied,’ says Serra. ‘As an experimentalist, I have to focus on the data itself instead of the interpretation. If we see something that differs from the prediction, it’s crucial to understand if the pattern is real or not.’

    If there’s a deviation from the prediction, experimentalists try to understand if something is wrong with the data. Only once all of the machine systematics and statistics are checked and double-checked can they say, with certainty, that there is a true discrepancy.

    ‘The experimental paper only shows the data. The theory paper is the one that gives the interpretation. Both are pieces of a puzzle and they fit together nicely,’ says Joaquim Matias, a theorist from Autonomous University of Barcelona and one of the paper’s authors. ‘The experimentalists found deviations and the theorists showed that they can be explained within a consistent picture for the first time.’”

    See the full article here.

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  • richardmitnick 7:36 am on July 25, 2013 Permalink | Reply
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    From CERN: “Standard Model held strong at EPS conference” 

    CERN New Masthead

    25 July 2013
    Ashley Jeanne Wennersherron

    “This year’s European Physical Society High-Energy Physics conference, which came to an end yesterday, was packed with results from the Large Hadron Collider.

    The most recent results on new boson discovered last year were presented by ATLAS and CMS – all of which indicate that the particle is a Higgs boson of the kind predicted by the Standard Model. Further studies are needed to pin down all of the boson’s properties.

    std
    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.

    The CMS and LHCb collaborations both presented the most recent analyses of a Bs (pronounced B-sub-s) particle decaying into two muons. The two experiments measured this decay at more than 4 sigma, meaning that there is very little chance that this is a statistical fluctuation. These measurements are also in good agreement with the Standard Model. If the measurements deviated even slightly from the predictions, it would be a clear sign of new physics.

    Out of the wealth of results on the physics of the top quark presented by ATLAS and CMS, the CMS collaboration announced the first observation of a rare process: the associated production of a single top quark and a W boson. Both ATLAS and CMS had previously seen evidence for this process but not to this significance of more than 5 sigma. The observation confirms the Standard Model prediction.

    All four of the large LHC experiments, ALICE, ATLAS, CMS and LHCb, presented results from the first proton-lead run at the accelerator. Earlier runs with collisions between two beams of lead nuclei (each nucleus containing a total of 208 protons and neutrons) indicated that a hot, dense medium results. In this material, quarks and gluons float unbound. First results now suggest that a similar system is created in proton-lead collisions, despite there being far fewer neutrons and protons. Further analysis is needed to understand these unexpected features.

    During the conference, the EPS recognized several collaborations and individual scientists for the work done to further the field of physics. In particular, the High-Energy Physics prize honoured the work of ATLAS and CMS for their discovery of a Higgs boson.”

    See the full article here.

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  • richardmitnick 5:19 pm on April 24, 2013 Permalink | Reply
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    From CERN and Symmetry Magazine: “LHCb experiment observes new matter-antimatter difference” 

    CERN New Masthead

    24 Apr 2013
    No Writer Credit

    lhcb
    A view of the LHCb underground area, looking upwards from the cavern floor (Image: Anna Pantelia/CERN)

    “The LHCb collaboration at CERN today submitted a paper to Physical Review Letters on the first observation of matter-antimatter asymmetry in the decays of the particle known as the B0s. It is only the fourth subatomic particle known to exhibit such behaviour.

    Matter and antimatter are thought to have existed in equal amounts at the beginning of the universe, but today the universe appears to be composed essentially of matter. By studying subtle differences in the behaviour of particle and antiparticles, experiments at the LHC are seeking to cast light on this dominance of matter over antimatter.

    Now the LHCb experiment has observed a preference for matter over antimatter known as CP-violation in the decay of neutral B0s particles. The results are based on the analysis of data collected by the experiment in 2011. ‘The discovery of the asymmetric behaviour in the B0S particle comes with a significance of more than 5 sigma – a result that was only possible thanks to the large amount of data provided by the LHC and to the LHCb detector’s particle identification capabilities,’ says Pierluigi Campana, spokesperson of the LHCb collaboration . ‘Experiments elsewhere have not been in a position to accumulate a large enough number of B0s decays.’

    Violation of the CP symmetry was first observed at Brookhaven Laboratory in the US in the 1960s in neutral particles called kaons. About 40 years later, experiments in Japan and the US found similar behaviour in another particle, the B0 meson. More recently, experiments at the so-called B factories and the LHCb experiment at CERN have found that the B+ meson also demonstrates CP violation.

    All of these CP violation phenomena can be accounted for in the Standard Model, although some interesting discrepancies demand more detailed studies. ‘We also know that the total effects induced by Standard Model CP violation are too small to account for the matter-dominated universe,’ says Campana. ‘However, by studying these CP violation effects we are looking for the missing pieces of the puzzle, which provide stringent tests of the theory and are a sensitive probe for revealing the presence of physics beyond the Standard Model.’”

    See the full CERN article here.

    And now a different slant from Symmetry Magazine

    Strange beauty particle decays boost matter

    lhcb2
    Photo: CERN via Symmetry Magazine

    April 24, 2013
    Kelly Izlar

    “When the universe was less than a minute old, a tiny difference in the behavior of matter and antimatter led to the matter-dominated existence we experience today.

    Today, particle physicists on CERN’s LHCb collaboration announced that, for the first time, they have observed particles called strange beauty mesons, or B0s, contributing to this imbalance.

    Scientists found that in strange beauty particles, composed of beauty antiquarks bound with strange quarks, antimatter decays slightly more often than matter. This is called charge-parity, or CP, violation.

    When B0s mesons decay to kaons and pions, physicists can determine if the new particles are matter or antimatter by looking at their relative charges. After comparing the number of matter particles with antimatter particles, they were able to confirm the findings.

    ‘It’s a simple idea, although getting there is quite complicated, says Tara Shears, a physicist on LHCb. ‘We’re looking at a very small discrepancy that reflects the nature of the universe.’

    LHCb’s result has a statistical significance exceeding five sigma—the gold standard for declaring a discovery in particle physics.

    ‘We had about one thousand B0s candidates to measure,’ says Shears. ‘The results unambiguously support predictions that these particles violate CP.’

    In the 1960s, James Cronin and Val Fitch observed CP violation in neutral kaons. About 40 years later, another particle, the B0 meson, showed similar behavior in the BaBar and Belle detectors in the United States and Japan. Recently, these experiments and LHCb also observed CP violation effects in B+ meson decays.

    However, the Standard Model predicts only a tiny portion of the amount of CP violation needed to explain the huge deficit of antimatter in the universe. While these results help scientists understand the mechanics of CP violation, the case of the missing antimatter remains unsolved.

    “We expected a certain amount of CP violation to be found in the strange beauty system,” says Pierluigi Campana, the LHCb spokesperson. “But finding the missing fraction of CP violation in the early universe will be new physics, which the Standard Model can’t predict.”

    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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