Cold Nuclear Matter Effects on Open and Hidden Heavy Flavor Production at the LHC. PDF Download

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Languages : en
Pages : 11

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Category :
Languages : en
Pages : 24

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The charmonium yields are expected to be considerably suppressed if a deconfined medium is formed in high-energy heavy-ion collisions. In addition, the bottomonium states, with the possible exception of the [Upsilon](1S) state, are also expected to be suppressed in heavy-ion collisions. However, in proton-nucleus collisions the quarkonium production cross sections, even those of the [Upsilon](1S), scale less than linearly with the number of binary nucleon-nucleon collisions. These 'cold nuclear matter' effects need to be accounted for before signals of the high density QCD medium can be identified in the measurements made in nucleus-nucleus collisions. We identify two cold nuclear matter effects important for midrapidity quarkonium production: 'nuclear absorption', typically characterized as a final-state effect on the produced quarkonium state and shadowing, the modification of the parton densities in nuclei relative to the nucleon, an initial-state effect. We characterize these effects and study their energy and rapidity dependence.

Author: Christopher Ghanim Yaldo
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Category : Cold fusion
Languages : en
Pages : 162

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In heavy-ion collisions at RHIC and the LHC, a suppression of the nuclear modification factor for jets along with other strongly interacting particles has been observed relative to proton-proton collisions. To unambiguously determine if this suppression is due to the creation of a strongly interacting medium of de-confied partons referred to as the Quark-Gluon Plasma, or due to Cold Nuclear Matter effects, a "control experiment" is required. Proton-lead collisions serve as this control experiment, because these colli- sions are expected to be sensitive to cold nuclear matter effects while not producing a QGP at this collision energy ({591}sNN = 5.02 TeV). Presented in this defense are the first measurements of charged + neutral jets in p-Pb collisions using the ALICE detector at the LHC. Measurements of CNM effects are done via the nuclear modification factor for jets: RpPb, RCP, and the jet structure ratio. Measurements of the jet spectrum along with a detailed and proper discussion of the statistical, systematic, and normalization uncertain- ties will be presented. Also a comparison of RpPb and RCP measured in this analysis to other measured RpPb and RCP from ATLAS and CMS will be presented. All the measurements performed in this analysis indicate that no strong cold nuclear matter effects are observed in p-Pb collisions using the ALICE detector at the LHC.

Author: Rebecca Michelle Scott
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Category : Collisions (Nuclear physics)
Languages : en
Pages : 152

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This dissertation presents a measurement of the yield and cross section of electrons from heavy flavor decays at central rapidity in proton-lead collisions measured by the ALICE (A Large Ion Collider Experiment) detector at the Large Hadron Collider. This analysis extends the transverse momentum reach of an earlier measurement in ALICE and the comparison is shown. The cross section of single electrons in proton-lead collisions is compared to the value expected in the absence of nuclear modication from proton-proton collisions. The cross section is well described by the perturbative Quantum Chromodynamics and no statistically signicant alteration due to hot nuclear matter effects is observed. The results are also compared to other measurements of heavy flavor and collision systems.

Author: Yun Tian
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Languages : en
Pages :

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ATLAS measurements of the production of muons from heavy flavor decays in √sNN = 2.76 TeV Pb+Pb collisions and √s = 2.76 TeV pp collisions at the LHC are presented. Integrated luminosities of 0.14 nb−1 and 570 nb−1 are used for the Pb+Pb and pp measurements, respectively. The measurements are performed over the transverse momentum range 4

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Category :
Languages : en
Pages : 185

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This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the proton and nucleus structure at high energy to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photo-production in nucleus-nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7th Framework Programme.

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Languages : en
Pages : 70

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This article reviews several important results from RHIC experiments and discusses their implications. They were obtained in a unique environment for studying QCD matter at temperatures and densities that exceed the limits wherein hadrons can exist as individual entities and raises to prominence the quark-gluon degrees of freedom. These findings are supported by major experimental observations via measuring of the bulk properties of particle production, particle ratios and chemical freeze-out conditions, and elliptic ow; followed by hard probe measurements: high-pT hadron suppression, dijet fragment azimuthal correlations, and heavy favor probes. These measurements are presented for particles of different species as a function of system sizes, collision centrality, and energy carried out in RHIC experiments. The results reveal that a dense, strongly-interacting medium is created in central Au + Au collisions at p sNN = 200 GeV at RHIC. This revelation of a new state of nuclear matter has also been observed in measurements at the LHC. Further, the IP-Glasma model coupled with viscous hydrodynamic models, which assumes the formation of a QGP, reproduces well the experimental ow results from Au + Au at p sNN = 200 GeV. This implies that the fluctuations in the initial geometry state are important and the created medium behaves as a nearly perfect liquid of nuclear matter because it has an extraordinarily low ratio of shear viscosity to entropy density, =s 0.12. However, these discoveries are far from being fully understood. Furthermore, recent experimental results from RHIC and LHC in small p + A, d + Au and 3He+Au collision systems provide brand new insight into the role of initial and final state effects. These have proven to be interesting and more surprising than originally anticipated; and could conceivably shed new light in our understanding of collective behavior in heavy-ion physics. Accordingly, the focus of the experiments at both facilities RHIC and the LHC is on detailed exploration of the properties of this new state of nuclear matter, the QGP.

Author: Yujiao Chen
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Category :
Languages : en
Pages :

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Furthermore, the pT dependence of the relative muon yields in Pb+Pb collisions to p+p colli- sions with the same center of mass collision energy per nucleon is presented by the nuclear modification factor RAA, which is defined as the ratio of a spectrum from heavy ion collisions to the same but scaled spectrum from nucleon-nucleon collisions . The observed RAA has little dependence on pT within the uncertainties quoted here. The results for RAA indicate a factor of about 3 suppression in the yield of muons in the most central (0-10%) collisions compared to the p+p collisions.

Author: Archil Garishvili
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Category :
Languages : en
Pages : 108

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The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory with its muon spectrometer has the ability to detect muons over the range of pseudorapidity 1:1

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Category :
Languages : en
Pages : 98

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In the initial years of operation, experiments at the Relativistic Heavy Ion Collider (RHIC) have identified a new form of matter formed in nuclei-nuclei collisions at energy densities more than 100 times that of a cold atomic nucleus. Measurements and comparison with relativistic hydrodynamic models indicate that the matter thermalizes in an unexpectedly short time, has an energy density at least 15 times larger than needed for color deconfinement, has a temperature about twice the critical temperature predicted by lattice QCD, and appears to exhibit collective motion with ideal hydrodynamic properties--a 'perfect liquid' that appears to flow with a near-zero viscosity to entropy ratio--lower than any previously observed fluid and perhaps close to a universal lower bound. However, a fundamental understanding of the medium seen in heavy-ion collisions at RHIC does not yet exist. The most important scientific challenge for the field in the next decade is the quantitative exploration of the new state of nuclear matter. That will require new data that will, in turn, require enhanced capabilities of the RHIC detectors and accelerator. In this report we discuss the scientific opportunities for an upgraded RHIC facility --RHIC II--in conjunction with improved capabilities of the two large RHIC detectors, PHENIX and STAR. We focus solely on heavy flavor probes. Their production rates are calculable using the well-established techniques of perturbative QCD and their sizable interactions with the hot QCD medium provide unique and sensitive measurements of its crucial properties making them one of the key diagnostic tools available to us.