共查询到20条相似文献,搜索用时 46 毫秒
1.
Xianglei Zhu 《Central European Journal of Physics》2012,10(6):1345-1348
We report on the p T dependence of nuclear modification factors (R CP) for K S 0 , ??, ?? and the $\bar NK_S^0 $ ratios at mid-rapidity from Au+Au collisions at $\sqrt {s_{NN} } $ = 39, 11.5 and 7.7 GeV. At $\sqrt {s_{NN} } $ = 39 GeV, the R CP data show a baryon/meson separation at intermediate p T and a suppression for K S 0 for p T up to 4.5 GeV/c; the $\bar \Lambda K_S^0 $ shows baryon enhancement in the most central collisions. However, at $\sqrt {s_{NN} } $ = 11.5 and 7.7 GeV, R CP shows less baryon/meson separation and $\bar NK_S^0 $ shows almost no baryon enhancement. These observations indicate that the matter created in Au+Au collisions at $\sqrt {s_{NN} } $ = 11.5 or 7.7 GeV might be distinct from that created at $\sqrt {s_{NN} } $ = 39 GeV. 相似文献
2.
We analyze longitudinal pion spectra from $\ensuremath \sqrt{s_{NN}}=2$ GeV to $\ensuremath \sqrt{s_{NN}}=20$ GeV within Landau??s hydrodynamical model and the UrQMD hybrid approach. From the measured data on the widths of the pion rapidity spectra, we extract the sound velocity c s 2 in the dense stage of the reactions. It is found that the sound velocity has a local minimum (indicating the softest point in the equation of state, EoS) at $\ensuremath \sqrt{s_{NN}}=4\mbox{--}9$ GeV, an energy range accessible at the Facility for Antiproton and Ion Research (FAIR) as well as the RHIC-Beam Energy Scan (RHIC-BES). This softening of the EoS is compatible with the formation of a QGP at the onset of deconfinement. The extracted sound velocities are then used to calculate an excitation function for the mean transverse mass of pions from the hybrid model. We find that, above $\ensuremath \sqrt{s_{NN}} \approx 10$ GeV, even the lowest c s 2 gives a considerably larger $\ensuremath \langle m_T\rangle$ of pions compared to data. 相似文献
3.
Zhongbao Yin 《Central European Journal of Physics》2012,10(6):1361-1364
We present the results on elliptic flow with multi-strange baryons produced in Pb-Pb collisions at $\sqrt {s_{NN} } $ = 2.76 TeV. The analysis is performed with the ALICE detector at LHC. Multi-strange baryons are reconstructed via their decay topologies and the v 2 measurements are analyzed with the two-particle scalar product method. The p T differential v 2 values are compared to the viscous hydrodynamical (VISH2+1) model calculation and to the STAR measurements in Au-Au collisions at $\sqrt {s_{NN} } $ = 200 GeV. We found that the model describes ?? and ??v 2 measurements within uncertainties. The differential v 2 of ?? and ?? is similar to the STAR measurements at 200 GeV in Au-Au collisions. 相似文献
4.
Thomas S. Ullrich 《Acta Physica Hungarica A》2004,21(2-4):143-150
Inclusive spectra of charged particles at midrapidity in Au+Au collisions at $\sqrt {s_{NN} } = 130$ GeV and 200 GeV were measured with the STAR detector at RHIC. The measured mean transverse momentum 〈p T 〉 shows a characteristic dependence on charged particle multiplicity and beam energy in Au+Au collisions that is distinctly different from pp, $p\bar p$ and e+e? collisions. A 32%±3%(syst) increase in 〈p T 〉 from pp to Au+Au collisions was observed at 200 GeV. While the charged multiplicity was found to increase by 19%±5%(syst) from $\sqrt {s_{NN} } = 130$ GeV to 200 GeV, no significant difference in 〈p T 〉 was found between the two energies. A comparison with model predictions is discussed. 相似文献
5.
T. Tarnowsky 《Physics of Atomic Nuclei》2012,75(5):546-549
Results from new measurements of dynamical K/?? and p/?? ratio fluctuations are presented. Dynamical fluctuations in global conserved quantities such as baryon number, strangeness, or charge may be observed near a QCD critical point. The STAR experiment has previously acquired data in AuAu collisions at the energies $\sqrt {s_{NN} }$ = 200, 130, 62.4, and 19.6 GeV and CuCu collisions at $\sqrt {s_{NN} }$ = 200, 62.4, and 22.4 GeV. The commencing of a QCD critical point search at RHIC has extended the reach of possible measurements of dynamical K/?? and p/?? ratio fluctuations from AuAu collisions to lower energies. New results are compared to previous measurements and to theoretical predictions from the UrQMD model. 相似文献
6.
Alexander Bazilevsky 《Acta Physica Hungarica A》2004,21(2-4):101-105
We present PHENIX recent results on charged particle and transverse energy densities measured at mid-rapidity in Au?Au collisions at $\sqrt {s_{NN} } = 130$ GeV and 200 GeV over a broad range of centralities. The mean transverse energy per charged particle is derived. The first PHENIX measurements at $\sqrt {s_{NN} } = 19.6$ GeV are also presented. A comparison with calculations from various theoretical models is performed. 相似文献
7.
Bedangadas Mohanty 《Pramana》2014,83(5):705-712
Two measurements related to the proton and antiproton production near midrapidity in \(\sqrt {s_{{NN}}} = 7.7\) , 11.5, 19.6, 27, 39, 62.4 and 200 GeV Au+Au collisions using the STAR detector at the Relativistic Heavy Ion Collider (RHIC) are discussed. At intermediate impact parameters, the net-proton midrapidity dv 1/dy, where v 1 and y are directed flow and rapidity, respectively, shows non-monotonic variation as a function of beam energy. This non-monotonic variation is characterized by the presence of a minimum in dv 1/dy between \(\sqrt {s_{NN}} = 11.5\) and 19.6 GeV and a change in the sign of dv 1/dy twice between \(\sqrt {s_{{NN}}}\) = 7.7 and 39 GeV. At small impact parameters the product of the moments of net-proton distribution, kurtosis × variance (κ σ 2) and skewness × standard deviation (S σ) are observed to be significantly below the corresponding measurements at large impact parameter collisions for \(\sqrt {s_{{NN}}}\) = 19.6 and 27 GeV. The κ σ 2 and S σ values at these beam energies deviate from the expectations from Poisson statistics and that from a hadron resonance gas model. Both these measurements have implications towards understanding the quantum chromodynamics (QCD) phase structures, the first-order phase transition and the critical point in the high baryonic chemical potential region of the phase diagram. 相似文献
8.
Gary D. Westfall 《Acta Physica Hungarica A》2004,21(2-4):249-254
The balance function is based on the principle that charge is locally conserved when particles are pair produced. Balance functions have been measured for all charged pairs, identified pion pairs, and identified charged kaon pairs in Au+Au collisions at $\sqrt {s_{NN} } = 200$ GeV and p+p collisions at $\sqrt {s_{NN} } = 200$ GeV at the Relativistic Heavy Ion Collider using STAR. Balance functions for all charged particles from Au+Au scale smoothly with centrality to the p+p value. Balance functions for charged particles and pions are narrower in central collisions than in peripheral collisions consistent with trends predicted by models incorporating the concept of late hadronization. Balance functions for kaon pairs represent a strangeness balance. Balance functions for kaons are narrower than those for pion pairs and may show less dependence on centrality. 相似文献
9.
A. Ya. Berdnikov D. A. Ivanishchev D. O. Kotov V. G. Riabov Yu. G. Riabov V. M. Samsonov 《Bulletin of the Russian Academy of Sciences: Physics》2013,77(7):904-907
The production of dielectron pairs is measured in PHENIX experiment during p + p, d + Au, Cu + Cu, and Au + Au collisions at $\sqrt {s_{NN} }$ = 200 GeV. In the mass region between φ and J/ψ mesons, the yield is consistent with expectations from correlated production. In the mass region below φ mesons, the p + p and d+ Au spectra are well described by known contributions from light meson decays. In contrast, the Au + Au minimum bias spectrum in this region is enhanced by a factor of 4.7, concentrated at low p T < 1.5 GeV/s and rapidly rising with centrality. Existing theoretical models cannot describe the observed enhancement. 相似文献
10.
V. P. Ladygin A. P. Jerusalimov N. B. Ladygina 《Physics of Particles and Nuclei Letters》2010,7(5):349-354
The measurement of Λ0-hyperon polarization in nucleus-nucleus collisions is considered as one of possible tools to study the phase transition. Fixed target and collider experiments are discussed for the case of λ0 production from Au-Au central collisions at $ \sqrt {s_{NN} } $ of about several GeV. 相似文献
11.
Yifei Zhang Haojie Xu Wangmei Zha Qun Wang 《Central European Journal of Physics》2012,10(6):1352-1356
We reproduce di-electron spectra in the region of 0 < m e+e < 4 GeV in both minimum bias and central Au+Au collisions at $\sqrt {s_{NN} } $ = 200 GeV measured by the STAR experiment. A cocktail simulation, incorporating STAR acceptance and detector responses, is able to describe the ??enhancement?? of the low mass region by including an in-medium modification of vector mesons and a thermal di-lepton calculation. We also predict the di-lepton mass spectra in RHIC lower energies via an extrapolation method. The evolution of Di-lepton mass spectra, effective temperature, and possible medium modifications versus colliding energies are studied to explore the QCD phase diagram. 相似文献
12.
Raimond Snellings 《Acta Physica Hungarica A》2004,21(2-4):237-242
In these proceedings some of the highlights of the elliptic flow measurements from STAR at $\sqrt {s_{NN} } = 130$ and 200 GeV for Au + Au collisions are presented. 相似文献
13.
14.
Christina Markert 《Acta Physica Hungarica A》2004,21(2-4):171-177
The recent results from resonance production in central Au+Au and p+p collisions at $\sqrt {s_{NN} } = 200$ GeV from the STAR experiment at RHIC are presented and discussed. 相似文献
15.
Felix Matathias 《Acta Physica Hungarica A》2006,25(2-4):303-312
Measurements of identified particle production with the PHENIX experiment at RHIC have reached a mature state, where a multitude of nuclear systems at different colliding energies have been studied. The discovery configurations of $\sqrt {s_{NN} } = 130$ and 200 GeV Au+Au collisions have now been supplemented by additional Au+Au and Cu+Cu configurations at various energies, along with baseline p+p and d+Au runs at $\sqrt {s_{NN} } = 130$ GeV. In this work we present a systematic study of the Cronin effect in d+Au collisions and recent results from p+p collisions. We then proceed to make a critical comparison of pion, kaon and proton production in heavy ion and baseline systems, and discuss the observed nuclear effects on hadron production. 相似文献
16.
Hui Wang 《Central European Journal of Physics》2012,10(6):1282-1284
It has been suggested that the existence of a QCD phase transition would cause an increase and divergence of fluctuations. Thus event-by-event particle ratio fluctuations could be used to study strangeness and baryon number fluctuations near the critical point in the QCD phase diagram. In this paper, we present dynamical K/??, p/??, and K/p ratio fluctuations from Au+Au collisions at $\sqrt {s_{NN} } $ = 7.7 to 200 GeV. Charge dependent results as well as multiplicity scaling properties of these fluctuation results are discussed. The STAR data are compared to different theoretical model predictions and previous experimental results. 相似文献
17.
B. B. Back 《Acta Physica Hungarica A》2006,25(2-4):499-506
The PHOBOS Collaboration has measured charged particles emitted over the range ?5.4<η<5.4 for Au+Au collisions at energies of $\sqrt {s_{NN} } = 19.6$ , 62.4, 130 and 200 GeV. In this contribution I will present recent results on the pseudorapidity distributions, total charged-particle production, and collective flow of particles obtained from these measurements. 相似文献
18.
Levente Molnar 《Acta Physica Hungarica A》2006,25(2-4):293-301
We present STAR results from identified particle spectra measured in $\sqrt {s_{NN} } = 62.4$ GEV Au-Au collisions. Particle production and system dynamics are compared to results at $\sqrt {s_{NN} } = 200$ GeV. We extract kinetic and chemical freeze-out parameters using blast wave model parametrization and statistical model. We discuss the effect of resonance decays on the extracted kinetic freeze-out parameters. 相似文献
19.
F. Retière 《Acta Physica Hungarica A》2004,19(3-4):369-372
Ultra-relativistic heavy-ion collisions produced at RHIC differ significantly from a superposition of proton-proton collisions. Evidence of collective expansion has been gathered. The yield of high transverse momentum particles has been found to be lower in head-on Au?Au collisions than is expected by scaling p-p collisions. Di-jet processes, which are frequent in p-p collisions, are almost absent in head-on Au?Au collisions. The current results from RHIC indicate that Au?Au collisions at $\sqrt {S_{NN} } = 130$ GeV and $\sqrt {S_{NN} } = 200$ GeV yield an expanding system that is opaque to high momentum partons. 相似文献
20.
We outline the many quarkonium-physics opportunities offered by a multi-purpose fixed-target experiment using the p and Pb Large Hadron Collider (LHC) beams extracted by a bent crystal. This provides an integrated luminosity of 0.5 fb?1 per year on a typical 1?cm-long target. Such an extraction mode does not alter the performance of the collider experiments at the LHC. With such a high luminosity, one can analyse quarkonium production in great details in pp, pd and pA collisions at ${\sqrt{s_{NN}}\simeq 115}$ GeV and at ${\sqrt{s_{NN}}\simeq 72}$ GeV in PbA collisions. In a typical pp (pA) run, the obtained quarkonium yields per unit of rapidity are 2–3 orders of magnitude larger than those expected at RHIC and about, respectively, 10(70) times larger than for ALICE. In PbA, they are comparable. By instrumenting the target-rapidity region, the large negative-x F domain can be accessed for the first time, greatly extending previous measurements by Hera-B and E866. Such analyses should help resolving the quarkonium-production controversies and clear the way for gluon PDF extraction via quarkonium studies. The nuclear target-species versatility provides a unique opportunity to study nuclear matter and the features of the hot and dense matter formed in PbA collisions. A polarised proton target?allows the study of transverse-spin asymmetries in J/ψ and ${\Upsilon}$ production, providing access to the gluon and charm Sivers functions. 相似文献