4,033 research outputs found

    High-density QCD with CMS at the LHC

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    The capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC) are summarised. Various representative measurements in Pb-Pb collisions at sqrt(s) = 5.5 TeV are covered. These include "bulk" observables (charged hadron multiplicity, low-pT inclusive hadron spectra and elliptic flow) which provide information on the collective properties of the system; as well as perturbative processes (high-pT hadrons, jets, gamma-jet and quarkonium production) which yield "tomographic" information of the densest phases of the reaction.Comment: 8 pages, 7 figs. Proceeds plenary talk Quark-Matter'08, Jaipur, India. To appear in J. Phys.

    High-energy heavy-ions physics: from RHIC to LHC

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    A selection of experimental results in high-energy nucleus-nucleus collisions after five years of operation of the Relativistic Heavy-Ion Collider (RHIC) is presented. Emphasis is put on measurements that provide direct information on fundamental properties of high-density QCD matter. The new experimental opportunities accessible at LHC are introduced, in particular those that may help clarify some of the current open issues at RHIC.Comment: A few misprints corrected. Matches version to appear in NP

    Impact of LHC Run-1 on particle astrophysics

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    An overview of the impact of the first three years of LHC operation on two of the most important open questions in astroparticle physics is presented. Measurements in proton-proton collisions at the energy frontier that provide valuable information on the identity of the highest-energy particles in the cosmos as well as new constraints on the nature of dark matter, are summarized.Comment: 7 pages, 8 figures. Proceedings invited plenary talk at "2nd Intl. Conf. on New Frontiers in Physics" (ICNFP 2013) in Kolymbari, Crete. To appear in Eur.Phys.J.Con

    αs\alpha_s review (2016)

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    The current world-average of the strong coupling at the Z pole mass, αs(mZ2)=0.1181±0.0013\alpha_s(m^2_{Z}) = 0.1181 \pm 0.0013, is obtained from a comparison of perturbative QCD calculations computed, at least, at next-to-next-to-leading-order accuracy, to a set of 6 groups of experimental observables: (i) lattice QCD "data", (ii) τ\tau hadronic decays, (iii) proton structure functions, (iv) event shapes and jet rates in e+ee^+e^- collisions, (v) Z boson hadronic decays, and (vi) top-quark cross sections in p-p collisions. In addition, at least 8 other αs\alpha_s extractions, usually with a lower level of theoretical and/or experimental precision today, have been proposed: pion, Υ\Upsilon, W hadronic decays; soft and hard fragmentation functions; jets cross sections in pp, e-p and γ\gamma-p collisions; and photon F2_2 structure function in γγ\gamma\,\gamma collisions. These 14 αs\alpha_s determinations are reviewed, and the perspectives of reduction of their present uncertainties are discussed.Comment: 4 pages, 2 figures. Minor changes. Version submitted to Proceedings Moriond QCD 201

    Physics case of FCC-ee

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    The physics case for electron-positron beams at the Future Circular Collider (FCC-ee) is succinctly summarized. The FCC-ee core program involves e+ee^+e^- collisions at s\sqrt{s} = 90, 160, 240, and 350 GeV with multi-ab1^{-1} integrated luminosities, yielding about 1012^{12} Z bosons, 108^{8} W+^+W^- pairs, 106^{6} Higgs bosons and 4\cdot105^{5} ttˉt\bar{t} pairs per year. The huge luminosities combined with 100\cal{100} keV knowledge of the c.m. energy will allow for Standard Model studies at unrivaled precision. Indirect constraints on new physics can thereby be placed up to scales ΛNP\Lambda_{_{\rm NP}} \approx 7 and 100 TeV for particles coupling respectively to the Higgs and electroweak bosons.Comment: 8 pages, 6 figures. Proceedings LFC15: Physics Prospects for Linear and Other Future Colliders, ECT*, Trento, Oct. 201

    Physics at the FCC-ee

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    The physics program accessible in e+ee^+e^- collisions at the Future Circular Collider (FCC-ee) is summarized. The FCC-ee aims at collecting multi-ab1^{-1} integrated luminosities in e+ee^+e^- at s\sqrt{s} = 90, 160, 240, and 350 GeV, yielding 1012^{12} Z bosons, 108^{8} W+^+W^- pairs, 106^{6} Higgs bosons and 41054\cdot 10^{5} top-quark pairs per year. Such huge data samples combined with a O(100keV)\cal{O}(100 \rm keV) c.m. energy uncertainty will allow for Standard Model measurements with unparalleled precision and searches for new physics in regions not probed so far. The FCC-ee will be able to (i) indirectly discover new particles coupling to the Higgs and electroweak bosons up to scales Λ\Lambda \approx 7 and 100 TeV; (ii) perform competitive SUSY tests at the loop level in regions beyond the LHC reach; and (iii) achieve the best potential in direct collider searches for dark matter and sterile neutrinos with masses below 60 GeV.Comment: 8 pages, 8 figures. Proceedings 17th Lomonosov conference on Elementary Particle Physics, Moscow, Aug. 2015. World Scientific, to appear. arXiv admin note: text overlap with arXiv:1601.06640

    Higgs and Beyond the Standard Model physics with the FP420 detector at the LHC

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    The physics case of the FP420 R&D project aiming at the installation of proton detectors in the LHC tunnel at 420 m from the ATLAS and CMS interaction points, is presented. The motivations of the measurements accessible with FP420 -- exclusive Higgs production (pp --> p H p) and photon-induced processes (pp --> p gamma p --> p X p, pp --> p gamma gamma p --> p X p, where X is sensitive to new physics) -- are outlined.Comment: Proceedings Moriond-QCD 2009. 5 pages, 3 fig
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