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Journal of Physics G: Nuclear and Particle Physics, 2008
RHIC-PHENIX has observed a large suppression pattern and azimuthal anisotropy of non-photonic electron at mid-rapidity (| η |< 0.35) in Au+Au collisions at √ sNN = 200 GeV. To understand these results and the interaction of heavy quarks in the hot and dense medium, experimental determination of production ratio of charm over bottom is one of the most important topics, since the behavior of bottom may differ from charm in the medium. We measured the ratio of charm over bottom and total cross section of bottom via partial reconstruction of D 0 →e + K − νe decay in p+p collisions at √ s = 200 GeV. Total cross sections of charm and bottom were also measured via di-electron continuum in p+p collisions at √ s = 200 GeV.
Heavy quarkonia production in p+p collisions from the PHENIX experiment
Journal of Physics G: Nuclear and Particle Physics, 2007
Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs that interact with the collision medium during hadronization. These in-medium interactions convey information about the fundamental properties of the medium itself and can be used to examine the modification of the QCD confining potential in the collision environment. Baseline measurements from p+p and d+Au collision systems are used to distinguish cold nuclear matter effects while measurements from heavy ion collision systems are used to quantify in-medium effects. The PHENIX experiment has the capability of detecting heavy quarkonia at 1.2 < |η| < 2.2 via the µ + µ − decay channel and at |η| < 0.35 via the e + e − decay channel. Recent runs have resulted in the collection of high statistics p+p data sets that provide an essential baseline reference for heavy ion measurements and allow for further critical evaluation of heavy quarkonia production mechanisms. The latest PHENIX results for the production of the J/ψ in p+p collisions are presented and future prospects for ψ ′ , χ c and Υ measurements are discussed.
Heavy-quarkonium production in high energy proton-proton collisions at RHIC
Physical Review D, 2010
We update the study of the total ψ and Υ production cross section in proton-proton collisions at RHIC energies using the QCD-based Color-Singlet (CS) Model, including next-to-leading order partonic matrix elements. We also include charm-quark initiated processes which appear at leading order in α s , but which have so far been overlooked in such studies. Contrary to earlier claims, we show that the CS yield is consistent with measurements over a broad range of J/ψ rapidities. We also find that charm-quark initiated processes, including both intrinsic and sea-like charm components, typically contribute at least 20 % of the direct J/ψ yield, improving the agreement with data both for the integrated cross section and its rapidity dependence. The key signature for such processes is the observation of a charm-quark jet opposite in azimuthal angle φ to the detected J/ψ. Our results have impact on the proper interpretation of heavy-quarkonium production in heavy-ion collisions and its use as a probe for the quark-gluon plasma.
Open Heavy Flavor and Quarkonia Results at RHIC
2017
RHIC experiments carry out a comprehensive physics program which studies open heavy flavor and quarkonium production in relativistic heavy-ion collisions. The discovery at RHIC of large high-pT suppression and flow of electrons from heavy quarks flavors have altered our view of the hot and dense matter formed in central Au + Au collisions at SNN=200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. In recent years, the RHIC experiments upgraded the detectors; (1) PHENIX Collaboration installed silicon vertex tracker (VTX) at mid-rapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region, and (2) STAR Collaboration installed the heavy flavor tracker (HFT) and the muon telescope detector (MTD) both at the mid-rapidity region. With these new upgrades, both experiments have collected large data samples. These new detectors enhance the capability of heavy flavor measurements via precision tracking. The PHENIX e...
Highlights from PHENIX at RHIC
EPJ Web of Conferences, 2018
Hadrons conveying strange quarks or heavy quarks are essential probes of the hot and dense medium created in relativistic heavy-ion collisions. With hidden strangeness, φ meson production and its transport in the nuclear medium have attracted high interest since its discovery. Heavy quark-antiquark pairs, like charmonium and bottomonium mesons, are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into particles carrying open heavy flavor. In this context, the PHENIX collaboration carries out a comprehensive physics program which studies the φ meson production, and heavy flavor production in relativistic heavy-ion collisions at RHIC. In recent years, the PHENIX experiment upgraded the detector in installing silicon vertex tracker (VTX) at mid-rapidity region and forward silicon vertex tracker (FVTX) at the forward rapidity region. With these new upgrades, the experiment has collected large data samples, and enhanced the capability of heavy flavor measurements via precision tracking. This paper summarizes the latest PHENIX results concerning φ meson, open and closed charm and beauty heavy quark production in relativistic heavy-ion collisions. These results are presented as a function of rapidity, energy and system size, and their interpretation with respect to the current theoretical understanding. Until now, Quantum Chromodynamics (QCD) is considered the fundamental theory of the strong interaction between quarks and gluons. Conforming to QCD, at ordinary temperatures or densities this force confines the quarks into composite hadrons. However, when the temperature reaches the QCD energy scale or its density rises to the point where the average inter-quark separation is less than 1 fm, hadronic matter under extremely dense and hot conditions undergoes a phase transition to form a Quark-Gluon Plasma (QGP or QCD matter) in which quarks and gluons no longer are confined to the size of a hadron . Since the discovery of the QCD matter at the Relativistic Heavy Ion Colllider (RHIC) at Brookhaven National Laboratory (BNL), the perception of the properties of strongly interacting matter at high temperatures has been a central goal of our research. This task is carried out by making measurements of multiple observables over a large range of energies and collision systems. To achieve this goal, RHIC provided collisions of gold-gold (Au + Au), copper-copper (Cu + Cu), uranium-uranium (U + U), copper-gold (Cu + Au), deuteron-gold (d + Au), helium-gold ( 3 He + Au), proton-gold (p + Au) and proton-Aluminum
J/ψ suppression in heavy ion collisions at the CERN SPS
Progress in Particle and Nuclear Physics, 1999
We reexamine the production of J/ψ and other charmonium states for a variety of target-projectile choices at the SPS, in particular for the interesting comparison between S+U at 200 GeV/c and Pb+Pb at 158 GeV/c as observed in the experiments NA38 and NA50 respectively. For this study we use a newly constructed cascade code LUCIFER II, which yields acceptable descriptions of both hard and soft processes, specifically Drell-Yan and meson production. This code divides the ion-ion collision into an initial phase involving hard interactions of the original nucleons and no soft energy loss, followed after the meson formation time by a 'normal' low energy cascade among the secondary particles. The modeling of the charmonium states differs from that of earlier workers in its unified treatment of the hidden charm meson spectrum, which is introduced from the outset as a set of coupled states ψ, χ i , ψ ′ . The result is a description of the NA38 and NA50 data in terms of a conventional, hadronic picture. The apparently anomalous suppression found in the most massive Pb+Pb system arises in the present simulation from three sources: destruction in the initial nucleon-nucleon cascade phase, use of coupled channels to exploit the larger breakup in the less bound χ i and ψ ′ states, and comover interaction in the final low energy phase.
Hard probes in heavy ion collisions at the LHC: heavy flavour physics
We present the results from the heavy quarks and quarkonia working group. This report gives benchmark heavy quark and quarkonium cross sections for pp and pA collisions at the LHC against which the AA rates can be compared in the study of the quark-gluon plasma. We also provide an assessment of the theoretical uncertainties in these benchmarks. We then discuss some of the cold matter effects on quarkonia production, including nuclear absorption, scattering by produced hadrons, and energy loss in the medium. Hot matter effects that could reduce the observed quarkonium rates such as colour screening and thermal activation are then discussed. Possible quarkonium enhancement through coalescence of uncorrelated heavy quarks and antiquarks is also described. Finally, we discuss the capabilities of the LHC detectors to measure heavy quarks and quarkonia as well as the Monte Carlo generators used in the data analysis. VII CTEQ6M 4.75 1 1 with ¥ defined as above but now replaces. 2.1. Coverage in Charm Production We first study the range of c values that contribute to charm production. This question is relevant for understanding whether the current parameterizations of nuclear densities allow safe extrapolations. We also want to establish whether the constraints set by charm measurements in pPb collisions cover c ranges which are relevant for PbPb. As a reference, we shall use parameter set 8 U here and limit ourselves to LO predictions. We shall consider the full pseudorapidity range as well as limited pseudorapidity regions defined by the acceptance coverage typical of ALICE. In particular, we consider the central region, 1 1 g 0.9, and the forward region, 2.5 g g 4. The left (right) plot in Fig. 3.1 shows the differential rate distribution for production over the full (central) pseudorapidity range as a function of c d , the momentum fraction of partons in the beam traveling in the positive direction. The c 7 distribution is identical for pp and PbPb collisions, while the c d and c 7 distributions are interchanged for pPb and Pbp collisions. The same distributions, obtained for charm pairs in the forward pseudorapidity regions are given in Fig. 3.2, where the two peak structures (right peak) variables. In the case of central production, we note that the bulk of the cross section comes from c values peaked at 10 # t. The gluon density of the proton in this region is well known, thanks to the HERA data. No data are, however, available for the nuclear densities in this c region, at least not in a range of 7 relevant for charm production. We see that the c distributions for Pbp and PbPb collisions are very similar in shape. This suggests that a determination of nuclear corrections to the nucleon PDFs extracted from a Pbp run would be sufficient to properly predict the PbPb behaviour. In the case of forward production, the c ranges probed inside the two beams are clearly asym
Open and Hidden Charm in Proton–Nucleus and Heavy-Ion Collisions
International Journal of Modern Physics E, 2008
We review the collectivity and the suppression pattern of charmed mesons -produced in proton-nucleus and nucleus-nucleus collisions at SPS (∼ 158 A·GeV) and RHIC energies (∼ 21 A·TeV) -in comparison to dynamical and thermal models. In particular, we examine the charmonium 'melting' and the 'comover dissociation' scenarios -implemented in a microscopic transport approach -in comparison to the available data from the SPS and RHIC. The analysis shows that the dynamics of c,c quarks at RHIC are dominated by partonic or 'pre-hadronic' interactions in the strongly coupled plasma stage and can neither be modeled by 'hadronic' interactions nor described appropriately by color screening alone. Both the 'charmonium melting' and the hadronic 'comover absorption and recreation model' are found, however, to be compatible with the experimental observation at SPS energies; the experimental ratio of Ψ ′ /J/Ψ versus centrality clearly favors the 'hadronic comover' scenario. We find that the collective flow of charm in the purely hadronic Hadron-String Dynamics (HSD) transport appears compatible with the data at SPS energies, but substantially underestimates the data at top RHIC energies. Thus, the large elliptic flow v 2 of D-mesons and the low R AA (p T ) of J/Ψ seen experimentally have to be attributed to early interactions of non-hadronic degrees of freedom. Simultaneously, we observe that non-hadronic interactions are mandatory in order to describe the narrowing of the J/Ψ rapidity distribution from pp to central Au + Au collisions at the top RHIC energy of √ s = 200 GeV. We demonstrate additionally that the strong quenching of high-p T J/Ψ's in central Au + Au collisions indicates that a large fraction of final J/Ψ mesons is created by a coalescence mechanism close to the phase boundary. Throughout this review we, furthermore, provide predictions for charm observables from Au+Au collisions at FAIR energies of 25 -35 A·GeV.
Journal of High Energy Physics, 2012
The ALICE experiment at the LHC has studied J/ψ production at mid-rapidity in pp collisions at √ s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L int = 5.6 nb −1 . The fraction of J/ψ from the decay of long-lived beauty hadrons was determined for J/ψ candidates with transverse momentum p t > 1.3 GeV/c and rapidity |y| < 0.9. The cross section for prompt J/ψ mesons, i.e. directly produced J/ψ and prompt decays of heavier charmonium states such as the ψ(2S) and χ c resonances, is σ prompt J/ψ (p t > 1.3 GeV/c, |y| < 0.9) = 8.3 ± 0.8 (stat.) ± 1.1 (syst.) +1.5 −1.4 (syst. pol.) µb. The cross section for the production of b-hadrons decaying to J/ψ with p t > 1.3 GeV/c and |y| < 0.9 is σ J/ψ←h B (p t > 1.3 GeV/c, |y| < 0.9) = 1.46 ± 0.38 (stat.) +0.26 −0.32 (syst.) µb. The results are compared to QCD model predictions. The shape of the p t and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the bb pair total cross section and dσ /dy at midrapidity. * See Appendix A for the list of collaboration members Prompt J/ψ and beauty hadron production at mid-rapidity in pp collisions at √ s=7 TeV 3