LHC Results on Charmonium in Heavy Ions

In heavy-ion collisions at high energies, the quantum chromodynamics (QCD) predicts the production of the deconfined quark-gluon plasma (QGP) state. Quarkonia ($c\bar{c}$ or $b\bar{b}$ bound states) are a useful means to probe QGP and to investigate the behavior of QCD under the high parton-density environment. Up to now, the large hadron collider (LHC) at CERN provided two runs for PbPb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV in the years 2010 and 2011. The ALICE, ATLAS, and CMS experiments at LHC have analyzed the yields and spectra of the $J/\psi$ and $\Upsilon$ families. In this article, we review particularly the recent charmonium results in PbPb collisions at LHC from the 2010 run.Comment: to appear in the proceedings of The 5th International Workshop on Charm Physics (Charm 2012

Light-front wavefunction dependence of the quark recombination

We present an extension of the recombination formalism to analyze the effects from the variation of the hadron wavefunctions. The hadron spectra are sensitive to the shape of the wavefunctions. However, when we fit the wavefunction parameters to the physical observables, such as the average charge radius, the final spectra are very similar each other. We discuss our numerical results in comparison with the published PHENIX and STAR data at RHIC. In the hadron spectra, the recombination of thermal partons dominates at intermediate transverse momentum ($P_{T}$ = 2 $\sim$ 5 GeV), and the fragmentation dominates at high $P_{T}$ ($>$ 5 GeV). The yield ratios and the nuclear modification factors for various hadron species are also estimated and compared to the experimental data. We present a new prediction on $\bar{p}/p$ and $K^{-}/K^{+}$ ratios, including the jet quenching effects to the fragmentation mechanism.Comment: 26 pages, 7 figure

Kaon-nucleus scattering

Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering

The energy spectrum of forward photons measured by the RHICf experiment in sqrt{s} = 510 GeV proton-proton collisions

The Relativistic Heavy Ion Collider forward (RHICf) experiment aims at understanding the high-energy hadronic interaction by measuring the cross sections of very forward neutral particles in proton-proton collisions at $\sqrt{s}$ = 510 GeV. For the analysis of the photon measurement, the trigger efficiency and the particle identification performance are studied by using the Monte Carlo simulation data and the experimental data. In the RHICf operation, two kinds of trigger modes (Shower, HighEM) were implemented. The trigger efficiency of the Shower trigger is 100$\%$ for photons with the energies more than 20 GeV. The HighEM trigger is designed to detect high energy photons effectively, and the trigger efficiency of the HighEM trigger is 90$\%$ for photons with the energies more than 130 GeV. The correction factor for the photon identification is calculated by using the efficiency and purity. It is found that this correction does not make a sizeable effect on the shape of the energy spectrum because the energy dependency of the factor is small

Particle correlations and their implication to collectivity in pPb and PbPb from CMS

The long-range two-particle correlation functions reveal the near-side ridge structures in highmultiplicity pp, pPb and PbPb collisions at the Large Hadron Collider (LHC). The model that takes into account the collective flow originated from the initial-state geometry fluctuation can successfully describe the measured long-range correlation functions of charged particles. In this review paper, the recent experimental data on the long-range correlations and the extracted elliptic and triangular flow parameters in pPb and PbPb collisions from the Compact Muon Solenoid (CMS) experiment are summarized. The flow parameters from the longrange correlation analyses are compared with those from the multiparticle cumulants and the Lee-Yang Zeros (LYZ) method. In addition, the pseudorapidity dependence of long-range two-particle correlation functions in pPb and the deduced flow parameters for identified strange hadrons (KS0 and Λ/Λ̄) in pPb and PbPb are also presented to provide more insights on the long-range correlations and flow dynamics

CMS overview

Most recent CMS data related to the high-density QCD are presented for pp and PbPb collisions at 2.76 TeV and pPb collisions at 5.02 TeV. The PbPb collision is essential to understand collective behavior and the final-state effects for the detailed characteristics of hot, dense partonic matter, whereas the pPb collision provides the critical information on the initial-state effects including the modification of the parton distribution function in cold nuclei. This paper highlights some of recent heavy-ion related results from CMS

Overview of quarkonium production in heavy-ion collisions at LHC

Quarkonium has been regarded as one of the golden probes to identify the phase transition from confined hadronic matter to the deconfined quark-gluon plasma (QGP) in heavy-ion collisions. Recent data on the yields and momentum distributions of J/ψ and ϒ families in pp, pPb, and PbPb collisions at the Large Hadron Collider (LHC) are reviewed. The possible implications related to the propagation of quarkonia in the deconfined hot, dense matter and the modified parton distribution function (PDF) in cold nuclei are also discussed