共查询到20条相似文献,搜索用时 15 毫秒
1.
The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at √SNN=200GeV is systematically studied in a quark combination model.The pT spectra of π±,K±,P(p-)and A(A)in different centrality bins and the nuclear modification factors(Rcp)for these hadrons are calculated.The centrality dependence of the average collective transverse velocity(β(r)) for the hot and dense quark matter is obtained in Au+An collisions,and it is applied to a relative smaller Cu+Cu collision system.The centrality dependence of pT spectra and the Rcp for π0,K0/s and A in Cu+Cu collisions at √SNN=200 GeV are well described.The results show that(β(r))is only a function of the number of participants Npart and it is independent of the collision system. 相似文献
2.
The transverse momentum spectra for identified hadrons at different rapidities in central Au+Au collisions at = 200 GeV are studied in a quark combination model. The results for PT spectra of π±,K±, p(p-) and for the p/π ratios in a broader PT range at midrapidity agree well with the data. The transverse momentum spectra of pions, protons and antiprotons at various rapidities y 1, η= 2.2 and y≈3.2 are calculated and compared with the data. 相似文献
3.
按照夸克随机组合的简单组合模型,本文通过分析得出重子反重子比率与夸克反夸克平均产生几率的关系.进一步计算了相对论重离子碰撞过程中各种反粒子与粒子的比率,不需要任何额外假定, 预言的比率与RHIC加速器时Au Au碰撞STAR实验的结果基本一致.表明夸克组合模型能够解释相对论重离子碰撞过程的反粒子与粒子比率. 相似文献
4.
Using the Glauber model,we discuss the number of binary nucleon-nucleon collisions in heavy-ion collisions.Based on the latter,after considering the effect of energy loss of the nucleons in multiple colli- sions,we derive the pseudorapidity distribution of the multiplicity as a function of the impact parameter in nucleus-nucleus collisions.Using this,we analyze the experimental measurements carried out by the BRAHMS Collaboration in Au Au collisions at Pseudorapidity distribution of multiplicity in Au Au collisions at (S_(NN))~(1/2)=200 GeV)=200 GeV.The results are in good agreement with the experi- mental observations. 相似文献
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We investigate the squeezed back-to-back correlations(BBC) of K~+K~-, caused by the mass modification of particles in the dense medium formed in d + Au collisions at sNN~(1/2)= 200 GeV and Au + Au collisions at sNN~(1/2)= 62.4 GeV. Considering that some kaons may not be affected by the medium, we further study the BBC functions of K~+K~-when parts of all kaons have a mass-shift. Our results indicate that the BBC functions of K~+K~-can be observed when only ~10% of all kaons have a mass-shift in d + Au collisions at sNN~(1/2) = 200 GeV and the peripheral collisions of Au + Au at sNN~(1/2)= 62.4 GeV. Since the BBC function is caused by the mass-shift due to the interactions between the particle and the medium, the successful detection of the BBC function indirectly marks that the dense medium has formed in these collision systems. We suggest the experimental measurement of the BBC function of K~+K~- in d + Au collisions at sNN~(1/2) = 200 GeV and peripheral collisions of Au + Au at sNN~(1/2) = 62.4 GeV. 相似文献
7.
We perform a systematic study of elliptic flow(v_2) in Au+Au collisions at(~SNN)~(1/2) = 5 GeV by using a microscopic transport model, JAM. The centrality, pseudorapidity, transverse momentum and beam energy dependence of v_2 for charged as well as identified hadrons are studied. We investigate the effects of both the hadronic mean-field and the softening of equation of state(EoS) on elliptic flow. The softening of the EoS is realized by imposing attractive orbits in two body scattering, which can reduce the pressure of the system. We found that the softening of the EoS leads to the enhancement of v_2, while the hadronic mean-field suppresses v_2 relative to the cascade mode. It indicates that elliptic flow at high baryon density regions is highly sensitive to the EoS and the enhancement of v_2 may probe the signature of a first-order phase transition in heavy-ion collisions at beam energies of a strong baryon stopping region. 相似文献
8.
Kentaro Miki 《中国物理 C》2007,(12)
Azimuthal anisotropy of direct photon is measured in S_(NN)~(1/2)=200GeV Au Au collisions at RHIC- PHENIX.Direct photon is one of the most effective probes to study properties of hot dence medium at initial state(also QGP state)of heavy ion collisions because photons almost do not interact strongly with any other particles caused by its long mean free path and they keep their conditions when they axe created.Within statistical and systematic errors,the elliptic flow parameter(v_2)of direct photon is consistent with zero. Direct photon v_2 is estimated by hadron decay photon contamination are subtracted from inclusive photon v_2 in intermediate to high transverse momentum(p_T)region(0 to 10GeV/c)for 3 centrality selections(20% steps)and minimum bias. 相似文献
9.
Adler C Ahammed Z Allgower C Amonett J Anderson BD Anderson M Averichev GS Balewski J Barannikova O Barnby LS Baudot J Bekele S Belaga VV Bellwied R Berger J Bichsel H Bland LC Blyth CO Bonner BE Bossingham R Boucham A Brandin A Caines H Calderón De La Barca Sánchez M Cardenas A Carroll J Castillo J Castro M Cebra D Chattopadhyay S Chen ML Chen Y Chernenko SP Cherney M Chikanian A Choi B Christie W Coffin JP Conin L Cormier TM Cramer JG Crawford HJ DeMello M Deng WS Derevschikov AA Didenko L 《Physical review letters》2001,87(11):112303
The minimum-bias multiplicity distribution and the transverse momentum and pseudorapidity distributions for central collisions have been measured for negative hadrons ( h(-)) in Au+Au interactions at square root of ([s(NN)]) = 130 GeV. The multiplicity density at midrapidity for the 5% most central interactions is dN(h(-))/d(eta)/(eta = 0) = 280+/-1(stat)+/-20(syst), an increase per participant of 38% relative to pp collisions at the same energy. The mean transverse momentum is 0.508+/-0.012 GeV/c and is larger than in central Pb+Pb collisions at lower energies. The scaling of the h(-) yield per participant is a strong function of p( perpendicular). The pseudorapidity distribution is almost constant within /eta/<1. 相似文献
10.
We propose a forward method based on PYTHIA6.4 to study the jet properties in ultra-relativistic pp collisions.In the forward method,the partonic initial states are first generated with PYTHIA6.4 and then hadronized in the Lund string fragmentation model,and finally the hadronic jets are constructed from the created hadrons.Jet properties calculated with the forward method for pp collisions at √s=7 TeV are comparable to those calculated with the usual anti-kt algorithm(backward method)in PYTHIA6.4.The comparison between the backward and forward methods may contribute to the understanding of the partonic origin of jets in the backward method. 相似文献
11.
Arsene I Bearden IG Beavis D Besliu C Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Hansen O Holm A Ito H Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Kim EJ Kozik T Larsen TM Lee JH Lee YK Lindal S Lystad G Løvhøiden G Majka Z Makeev A McBreen B Mikelsen M Murray M Natowitz J Neumann B Nielsen BS Norris J Ouerdane D Płaneta R Rami F Ristea C Ristea O Röhrich D Samset BH Sandberg D Sanders SJ Scheetz RA Staszel P 《Physical review letters》2003,91(7):072305
We present spectra of charged hadrons from Au+Au and d+Au collisions at sqrt[s(NN)]=200 GeV measured with the BRAHMS experiment at RHIC. The spectra for different collision centralities are compared to spectra from p+(-)p collisions at the same energy scaled by the number of binary collisions. The resulting ratios (nuclear modification factors) for central Au+Au collisions at eta=0 and eta=2.2 evidence a strong suppression in the high p(T) region (>2 GeV/c). In contrast, the d+Au nuclear modification factor (at eta=0) exhibits an enhancement of the high p(T) yields. These measurements indicate a high energy loss of the high p(T) particles in the medium created in the central Au+Au collisions. The lack of suppression in d+Au collisions makes it unlikely that initial state effects can explain the suppression in the central Au+Au collisions. 相似文献
12.
R. Tenzer N. Grün W. Scheid 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,11(3):347-353
Total and differential cross-sections for the production of free electron-positron pairs are calculated for the reactions
Au79+ (10.8 GeV/u) on Cu29+, Ag47+ and Au79+. The methods used are the semiclassical approach and the solution of the time-dependent Dirac equation by a coupled channel
method with free wavepakets describing the created fermions. The obtained total cross-sections are in good agreement with
the experimental data. The differential cross-sections give informations about the correlation between the electron and positron.
Received 21 December 1999 and Received in final form 6 March 2000 相似文献
13.
Effects of centrality fluctuation and deuteron formation on the proton number cumulant in Au+Au collisions at s_(NN)~(1/2)=3 GeV from the JAM model 下载免费PDF全文
《中国物理C(英文版)》2021,(6)
We studied the effects of centrality fluctuation and deuteron formation on the cumulant(C_n) and correlation functions(k_n) of protons up to the sixth order in the most central(b3 fm) Au+Au collisions at s_(NN)~(1/2)=3 GeV in a microscopic transport model(JAM).The results are presented as a function of rapidity acceptance within the transverse momentum 0.4 p_T 2 GeV/c.We compared the results obtained by the centrality bin width correction(CBWC) using charged reference particle multiplicities with the CBWC using impact parameter bins.It was found that,at low energies,the centrality resolution for determining the collision centrality using charged particle multiplicities is not sufficient to reduce the initial volume fluctuation effect for higher-order cumulant analysis.New methods need to be developed to classify events with high centrality resolution for heavy-ion collisions at low energies.Finally,we observed that the formation of deuterons suppresses the higher-order cumulants and correlation functions of protons and found it to be similar to the efficiency effect.This work can serve as a noncritical baseline for the QCD critical point search in the high baryon density region. 相似文献
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《中国物理C(英文版)》2019,(12)
This work uses the Boltzmann transport model to study the thermal production of J/ψ and ψ(2S) in the quark gluon plasma(QGP) produced by (sNN)~(1/2)=5.02 TeV Pb-Pb collisions.The J/ψ nuclear modification factors are studied in detail alongside the mechanisms of primordial production and the recombination of charm and anti-charm quarks in the thermal medium.The ψ(2S) binding energy is much smaller in the hot medium compared to the ground state;thus,ψ(2S) with middle to low p_T can be thermally regenerated in the later stages of QGP expansions,enabling ψ(2S) to inherit larger collective flows from the bulk medium.We quantitatively study the nuclear modification factors of both J/ψ and ψ(2S) in different centralities and transverse momentum bins for (sNN)~(1/2)=5.02 TeV PbPb collisions. 相似文献
16.
将核子-核子碰撞末态带电粒子的生成源分为二元核子 核子碰撞与带头粒子两部分, 给出了末态带电粒子的赝快度分布与入射能量间的解析关系。 以此为基础, 将核 核碰撞末态带电粒子的生成源分为二元核子-核子碰撞、 带头粒子与旁观者3部分, 建立起了以碰撞参数与束流能量为自变量的末态带电粒子的赝快度分布, 并用其分析了BNL-RHIC-PHOBOS合作组在sNN=200 GeV的不同d+Au对心度碰撞中所做的实验测量。 所得结果与实验符合得很好。 We divide the particle generating sources in nucleon-nucleon collisions into two parts: binary collisions and leading particles, and present the analytical relation between charged particle pseudorapidity distributions and incident energy. On the basis of this work, we classify the particle generating sources in nucleus-nucleus collisions into three parts:binary collisions,leading particles and spectators,and formulate the charged particle pseudorapidity distributions as the function of incident energy and impact parameter. We then analyze with the model the experimental measurements in d+Au collisions at sNN=200 GeV. The theoretical results are well consistent with experimental data. 相似文献
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Anisotropic emission of charged mesons and structure characteristic of emission source in heavy ion collisions at 1-2A GeV 下载免费PDF全文
Angular distributions of pious and kaons produced in heavy ion collisions at the low-energy end of high energies (1-2 A GeV) have been investigated by using a multisource ideal gas model. The model covers the expansions and movements of the emission sources, and it is related to the collective flows. By using the analytic expression and the Monte Carlo method, the azimuthal and polar angle distributions of mesons are calculated by the model and compared with the experimental data of the KaoS Collaboration. 相似文献
19.
Adler SS Afanasiev S Aidala C Ajitanand NN Akiba Y Al-Jamel A Alexander J Aoki K Aphecetche L Armendariz R Aronson SH Atomssa ET Averbeck R Awes TC Babintsev V Baldisseri A Barish KN Barnes PD Bassalleck B Bathe S Batsouli S Baublis V Bauer F Bazilevsky A Belikov S Bjorndal MT Boissevain JG Borel H Brooks ML Brown DS Bruner N Bucher D Buesching H Bumazhnov V Bunce G Burward-Hoy JM Butsyk S Camard X Chand P Chang WC Chernichenko S Chi CY Chiba J Chiu M Choi IJ Choudhury RK Chujo T Cianciolo V 《Physical review letters》2006,96(1):012304
J/psi production in d + Au and p + p collisions at square root of S(NN) = 200 GeV has been measured by the PHENIX experiment at rapidities -2.2 < y < +2.4. The cross sections and nuclear dependence of J/psi production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p + A results and to theoretical models. The observed nuclear dependence in d + Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parametrizations that fit deep-inelastic scattering and Drell-Yan data at lower energies. 相似文献
20.
In this paper, we describe a study of charged particle yield as a function of pT for K*(892)0 and φ (1020) mesons in proton-proton (pp) and Pb-Pb collisions at $\sqrt{{s}_{NN}}$=2.76 TeV in the central rapidity region of ∣y∣<0.5, in a pT range of 0<pT <15 GeV c−1 in pp collisions and in a pT range of 0<pT<20 GeV c−1 in Pb-Pb collisions. We also investigated a very important ratio, the nuclear modification factor, to study the effects of the medium in the most central region, i.e. 0%-5% centrality. For data simulation, we used the EPOS-LHC and EPOS-1.99 models. To check the validity of these models’ simulations, we compared the data obtained from these Monte Carlo simulation programs with ALICE experimental data for $\sqrt{{s}_{NN}}$=2.76 TeV. It was concluded that the models’ predictions for the φ-meson in pp and for the most central Pb-Pb collisions disagreed with the ALICE data, and that the difference increased with pT. This may be connected with the essential role of collective parton behaviors which could not have been taken into account by the models. For K*0 mesons, both programs gave almost the same predictions, and with pT in the interval pT>3 GeV c−1, the predictions were very close to the experimental data. Both models gave higher predictions for the soft pT interval and lower predictions for the hard interactions. The values of the RAA distributions were lower than unity and both models were very close to the ALICE data. It is very interesting that the models were not able to describe the pT distributions, but they gave good predictions for their ratios. This may possibly be due to parton collective behaviors. We observed some additional suppression of K*0 at low values of pT with respect to φ-mesons, which may be related to the role of the masses of the particles in soft interactions. The rising trend for RAA in the region from pT =10 GeV c−1 to 20 GeV c−1 observed by the ALICE experiment was absent for the φ-mesons. 相似文献