Net-Baryon and Net-Kaon Rapidity Distributions in Ultrarelativistic Heavy-Ion Collisions

In this paper, the gluon distribution is extracted from the KLR-AdS/CFT saturation model and used to investigate net-baryon and net-kaon rapidity distributions in ultrarelativistic heavy-ion collisions. With the same parameters of the saturation model fitting to HERA data and an χ² analysis of the overall constant C, the theoretical results are in good agreement with RHIC data in Au+Au collisions at √s=0.2 TeV. Then, we present the predictive results for net-baryon rapidity distributions in central Pb+Pb collisions at LHC energies of √s=2.76, 3.94, and 5.52 TeV, and give the corresponding values of d N/d y for net-baryon at y=0.     

Rapidity equilibration in d + Au and Au + Au systems

In a Relativistic Diffusion Model (RDM), the evolution of net-proton rapidity spectra with in heavy systems is proposed as an indicator for local equilibration and longitudinal expansion. The broad midrapidity valley recently discovered at RHIC in central Au + Au collisions at = 200 GeV suggests rapid local equilibration which is most likely due to deconfinement, and fast longitudinal expansion. Rapidity spectra of produced charged hadrons in d + Au and Au + Au systems at RHIC energies and their centrality dependence are well described in a three-sources RDM. In central collisions, about 19% of the produced particles are in the equilibrated midrapidity region for d + Au.     

Charged-particle pseudorapidity density distributions from Au+Au collisions at sqrt[s(NN)]=130 GeV

The charged-particle pseudorapidity density dN(ch)/d eta has been measured for Au+Au collisions at sqrt[s(NN)] = 130 GeV at RHIC, using the PHOBOS apparatus. The total number of charged particles produced for the 3% most-central Au+Au collisions for /eta/相似文献   

Identified particle distributions in pp and Au+Au collisions at square root of (sNN)=200 GeV

Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for square root of [sNN]=200 GeV pp and Au+Au collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central Au+Au collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.     

J/psi production versus centrality, transverse momentum, and rapidity in Au+Au collisions at square root sNN=200 GeV

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities -2.2相似文献   

Charged particle density distributions in Au + Au collisions at relativistic heavy-ion collider energies

Charged particle pseudorapidity distributions have been measured in Au+ Au collisions using the BRAHMS detector at RHIC. The results are presented as a function of the collision centrality and the center of mass energy. They are compared to the predictions of different parton scattering models and the important role of hard scattering processes at RHIC energies is discussed. Keywords. Relativistic heavy-ion collisions; charged hadron production; pseudorapidity distributions; centrality dependence; hard scattering processes.     

Transverse momentum and centrality dependence of high-pT nonphotonic electron suppression in Au+Au collisions at sqrt[s NN]=200 GeV

The STAR collaboration at the BNL Relativistic Heavy-Ion Collider (RHIC) reports measurements of the inclusive yield of nonphotonic electrons, which arise dominantly from semileptonic decays of heavy flavor mesons, over a broad range of transverse momenta (1.2相似文献   

Open charm production from d + Au collisions in STAR

Charmed hadrons are interesting observables in heavy ion collisions. They are becoming more accessible to experimental scrutiny at RHIC energies due to the increased production cross-section of charm with the larger centre-of-mass energy available at RHIC compared to SPS. One source of interest in charm production is due to the fact that gluon fusion dominates the charm production cross-section at high energy. Hence, a measurement of charm hadrons is directly sensitive to the gluon distributions of the colliding particles. In addition, any measurement of production at RHIC, and more importantly any observed suppression, must be compared to the overall production of pairs. A systematic study of charmed hadrons in all collision systems available at RHIC is therefore an invaluable experimental tool in the characterization of the matter produced at RHIC. In particular, d + Au collisions are a necessary step for the comparison of any possible modification of charm production in Au + Au collisions. We present preliminary results on D meson production from d + Au collisions in STAR at = 200 . Arrival of the final proofs: 26 July 2005 PACS: 13.20.Fc, 13.25.Ft, 25.75.-q, 24.85. + p     

Baryon deceleration and partonic plasma creation by strong chromofields in ultrarelativistic heavy-ion collisions

Strong chromofields generated at early stages of ultrarelativistic nuclear collisions may explain not only creation of the quark-gluon plasma but also collective deceleration of net baryons. This is demonstrated by solving classical equations of motion for baryonic slabs under the action of a time-dependent chromofield. We have studied sensitivity of the slab trajectories and their final rapidities to the initial strength and decay time of the chromofield, as well as to the back reaction of the produced plasma. By proper choice of the initial chromofield energy density we can reproduce significant baryon stopping, an average rapidity loss of about two units, observed for Au + Au collisions at RHIC. Using a Bjorken-like hydrodynamical model with the particle production source, we also study the evolution of partonic plasma produced as the result of the chromofield decay. Due to the delayed formation and expansion of plasma its maximum energy density is significantly lower than the initial energy density of the chromofield. It is shown that the fluctuations of the chromofield due to the stochastic distribution of color charges help to populate the midrapidity region in the net-baryon distribution. To fit the midrapidity data we need the chromofields with initial energy densities in the range of 30 to 60 GeV/fm³. Predictions of baryon stopping for Pb + Pb collisions at LHC energies are made.     

RHIC能区Au+Au碰撞中集合径向流的研究

利用相对论量子分子动力学模型RQMD,对RHIC能区s=200A GeV Au+Au碰撞的集体膨胀效应进行了研究,对散射粒子的横质量谱进行了分析.研究表明,在RHIC能区的重离子反应中存在有强的集合径向流.对单粒子谱的拟合结果给出Au+Au的源冻结温度为160MeV,平均径向流速度为0.6c.     

Transverse-mass dependence of two-pion correlations in Au+Au collisions at square root[s(NN)] = 130 GeV

Two-pion correlations in square root[s(NN)] = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at square root[s(NN)] = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R(out)/R(side)) is consistent with unity and independent of k(T).     

Partonic Flow and phi-Meson production in Au+Au collisions at sqrt radical sNN = 200 GeV

We present first measurements of the phi-meson elliptic flow (v2(pT)) and high-statistics pT distributions for different centralities from radical sNN=200 GeV Au+Au collisions at RHIC. In minimum bias collisions the v2 of the phi meson is consistent with the trend observed for mesons. The ratio of the yields of the Omega to those of the phi as a function of transverse momentum is consistent with a model based on the recombination of thermal s quarks up to pT approximately 4 GeV/c, but disagrees at higher momenta. The nuclear modification factor (R CP) of phi follows the trend observed in the K S 0 mesons rather than in Lambda baryons, supporting baryon-meson scaling. These data are consistent with phi mesons in central Au+Au collisions being created via coalescence of thermalized s quarks and the formation of a hot and dense matter with partonic collectivity at RHIC.     

Midrapidity Lambda and Lambda(macro) production in Au+Au collisions at the square root of [s(NN)]=130 GeV

We report the first measurement of strange (Lambda) and antistrange (Lambda macro) baryon production from square root of [s(NN)]=130 GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Rapidity density and transverse mass distributions at midrapidity are presented as a function of centrality. The yield of Lambda and Lambda; hyperons is found to be approximately proportional to the number of negative hadrons. The production of Lambda; hyperons relative to negative hadrons increases very rapidly with transverse momentum. The magnitude of the increase cannot be described by existing hadronic string fragmentation models alone.     

RHIC能区Au+Au非对心碰撞中的事件形状

利用相对论量子分子动力学模型RQMD,结合2π干涉学分析,对RHIC能区s=200AGeV Au+Au非对心碰撞的事件形状进行了研究.研究表明,HBT参数可以反映事件在坐标空间的非对称性,而不能直接给出事件在动量空间的压力梯度.另外,HBT参数对横动量的依赖关系对系统的空间–动量关联较为敏感.     

Midrapidity antiproton-to-proton ratio from Au+Au collisions at sqrt [s(NN)]=130 GeV

We report results on the ratio of midrapidity antiproton-to-proton yields in Au+Au collisions at sqrt[s(NN)] = 130 GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of /y/<0.5 and 0.4相似文献   

Production of secondaries in high-energy <Emphasis Type="Italic">d</Emphasis>+Au collisions

In the framework of the quark–gluon string model we calculate the inclusive spectra of secondaries produced in d+Au collisions at intermediate (CERN SPS) and at much higher (RHIC) energies. The results of numerical calculations at intermediate energies are in reasonable agreement with the data. At RHIC energies numerically large inelastic screening corrections (percolation effects) should be accounted for in the calculations. We extract these effects from the existing experimental data of RHIC on minimum-bias and central d+Au collisions. The predictions for p+Au interactions at LHC energy are also given.     

Pseudorapidity and centrality dependence of the collective flow of charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV

This paper describes the measurement of collective flow for charged particles in Au+Au collisions at sqrt[s(NN)]=130 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal hit anisotropy is presented over a wide range of pseudorapidity (-5.0相似文献   

Elliptic flow at SPS and RHIC: from kinetic transport to hydrodynamics

Anisotropic transverse flow is studied in Pb+Pb and Au+Au collisions at SPS and RHIC energies. The centrality and transverse momentum dependence at midrapidity of the elliptic flow coefficient v₂ is calculated in the hydrodynamic and low density limits. Hydrodynamics is found to agree well with the RHIC data for semicentral collisions up to transverse momenta of 1–1.5 GeV/c, but it considerably overestimates the measured elliptic flow at SPS energies. The low density limit LDL is inconsistent with the measured magnitude of v₂ at RHIC energies and with the shape of its p_t-dependence at both RHIC and SPS energies. The success of the hydrodynamic model points to very rapid thermalization in Au+Au collisions at RHIC and provides a serious challenge for kinetic approaches based on classical scattering of on-shell particles.     

RHIC能区Au+Au碰撞中HBT关联参数分析

利用相对论量子分子动力学模型RQMD,对RHIC能区s=200GeV/u Au+Au碰撞进行了2π干涉学分析,并讨论了HBT半径参数对横动量的依赖关系.研究表明,两粒子关联函数能够给出碰撞源在冻结时刻的时空拓扑信息,HBT半径参数能够较好地反映源的尺度和形状,但其对横动量的依赖关系并不能直接反映源的压缩性质,而是对粒子产生时源的空间–动量关联程度更为敏感.     

Rapidity dependence of antiproton-to-proton ratios in Au+Au collisions at square root of (sNN) = 130 GeV

Measurements, with the BRAHMS detector, of the antiproton-to-proton ratio at midrapidities and forward rapidities, are presented for Au+Au reactions at square root of [s(NN)] = 130 GeV, and for three different collision centralities. For collisions in the 0%-40% centrality range, we find N(&pmacr;)/N(p) = 0.64+/-0.04((stat))+/-0.06((syst)) at y approximately 0, 0.66+/-0.03+/-0.06 at y approximately 0.7, and 0.41+/-0.04+/-0.06 at y approximately 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The antiproton and proton rapidity densities vary differently with rapidity, and indicate a significant degree of collision transparency, although a net-baryon free midrapidity plateau (Bjorken limit) is not yet reached.