共查询到20条相似文献,搜索用时 15 毫秒
1.
《中国物理C(英文版)》2017,(7)
Recent LHC results on the appearance of sub-leading flow modes in Pb Pb collisions at 2.76 TeV, related to initial-state fluctuations, are analyzed and interpreted within the HYDJET++ model. Using the newly introduced Principal Component Analysis(PCA) method applied to two-particle azimuthal correlations extracted from the model calculations, the leading and sub-leading flow modes are studied as a function of the transverse momentum(p T) over a wide centrality range. The leading modes of the elliptic(v_2~((1))) and triangular(v_3~((1))) flow calculated with the HYDJET++ model reproduce rather well the v_2 {2} and v_3 {2} coefficients measured experimentally using the two-particle correlations. Within the p T 3 Ge V/c range, where hydrodynamics dominates, the sub-leading flow effects are greatest at the highest p T of around 3 Ge V/c. The sub-leading elliptic flow mode(v_2~((2))), which corresponds to the n = 2 harmonic, has a small non-zero value and slowly increases from central to peripheral collisions, while the sub-leading triangular flow mode(v_3~((2))), which corresponds to the n = 3 harmonic, is even smaller and does not depend on centrality. For n= 2, the relative magnitude of the effect measured with respect to the leading flow mode shows a shallow minimum for semi-central collisions and increases for very central and for peripheral collisions. For the n= 3 case, there is no centrality dependence. The sub-leading flow mode results obtained from the HYDJET++model are in rather good agreement with the experimental measurements of the CMS Collaboration. 相似文献
2.
Hadron Multiplicities in Pb+Pb Collisions at the Large Hadron Collider and Pomeron Loop Effects
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We study the pseudo-rapidity distribution of hadron multiplicities of high energy Pb+Pb collisions by using color glass condensate dynamics at LHC/ALICE in the fixed coupling case. It is found that after including the pomeron loop effects the charged hadron multiplicities at central rapidity are about 1500 for central Pb+Pb collisions, which are significantly smaller than the saturation based calculations, ~ 1700 ÷ 2500 and compatible with that based on a study of multiplicities in the fragmentation region. 相似文献
3.
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
4.
For a class of analytical parametrizations of the freeze-out state of relativistic heavy ion collisions, we perform a simultaneous analysis of the single-particle m ⊥-spectra and two-particle Bose-Einstein correlations measured in central Pb+Pb collisions at the CERN SPS. The analysis includes a full model parameter scan with χ2 confidence levels. A comparison of different transverse density profiles for the particle emission region allows for a quantitative discussion of possible model dependencies of the results. Our fit results suggest a low thermal freeze-out temperature T≈95±15 MeV and a large average transverse flow velocity \(\bar v_ \bot \approx 0.55 \pm 0.07\). Moreover, the fit favours a box-shaped transverse density profile over a Gaussian one. We discuss the origins and the consequences of these results in detail. In order to reproduce the measured pion multiplicity our model requires a positive pion chemical potential. A study of the pion phase-space density indicates μπ≈60 MeV for T=100 MeV. 相似文献
5.
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
6.
Debasish Das 《Pramana》2012,79(4):863-866
The study of formation of heavy quarkonia in relativistic heavy-ion collisions provides important insight into the properties of the produced high-density QCD medium. Lattice QCD studies show sequential suppression of quarkonia states with increasing temperature; which affirms that a full spectroscopy can provide us a thermometer for the matter produced under extreme conditions in relativistic heavy-ion collisions and one of the most direct probes of deconfinement. Muons from the decay of charmonium resonances are detected in ALICE experiment in p?+?p and Pb+Pb collisions with a muon spectrometer, covering the forward rapidity region (2.5?<?y?<?4). The analysis of the inclusive J/?? production in the first Pb+Pb data collected in the fall of 2010 at a centre of mass energy of $\sqrt{s_{\rm NN}}=2.76$ ?TeV is discussed. Preliminary results on the nuclear modification factor (R AA) and the central to peripheral nuclear modification factor (R CP) are presented. 相似文献
7.
8.
F. Guérin 《The European Physical Journal C - Particles and Fields》2007,49(1):143-148
ALICE (A Large Ion Collider Experiment) is the LHC detector dedicated to the study of nucleus–nucleus collisions, in which
the formation of the quark–gluon plasma (QGP) is expected. Heavy quarkonia, especially the Upsilon states, are relevant for
studying the QGP since they provide an essential probe of the earliest and hottest stages of heavy ion collisions. They will
be measured via their dimuon decay channel in ALICE in the muon spectrometer. The muon spectrometer performance has been studied
in simulations, the results will be presented with emphasis on the trigger efficiency and rate in Pb–Pb collisions. The expected
yields of Upsilon states will be extracted from a simulation based on a global fit of the dimuon mass spectra for different
collision centralities. 相似文献
9.
We examine the qualitative features of parton production through materialization in heavy-ion collisions within perturbative QCD, and estimate the magnitude of the resulting parton density created during the early stage of the collisions. The implications for “anomalous”J/? suppression observed in Pb+Pb collisions at the CERN SPS are discussed. We argue that theA-dependence of absorption ofJ/? by (partonic) comovers is steeper than assumed in most phenomenological models, because the absorption process is dominated by quasi-perturbative QCD interactions. Our argument is supported by results recently obtained in the framework of the parton cascade model. We predict significant “anomalous” suppression for Pb+Pb collisions at the CERN-SPS, but not for S+U collisions. 相似文献
10.
PACIAE, a parton and hadron cascade model, is utilized to systematically investigate strange particle production and strangeness enhancement in Au+Au collisions and in Pb+Pb collisions with the √sNN=200 GeV at the RHIC and 2.76 TeV at the LHC, respectively. The experimental results at different centralities, using data from the STAR collaboration and the ALICE collaboration, are well described by the PACIAE model. This may represent the importance of the parton and hadron rescatterings, as well as the reduction mechanism for strange quark suppression, that are implemented in the PACIAE model. 相似文献
11.
高能重离子碰撞中正负荷电粒子比单事例起伏研究 总被引:2,自引:0,他引:2
用强子和弦级联模型,JPCIAE及相应的Monte Carlo事例产生器,研究相对论性核–核碰撞中有限快度区间内正负荷电粒子比单事例起伏与能量、中心度、共振态衰变及快度间隔的关系.JPCIAE模型能够较好地符合CERN/SPS能区Pb+Pb碰撞的实验结果.本文还用此模型预言了RHIC能区Au+Au碰撞和ALICE能区Pb+Pb碰撞中的正负荷电粒子比单事例起伏.可以看出碰撞能量、中心度、共振态衰变及快度间隔对正负荷电粒子比单事例起伏的影响都不大. 相似文献
12.
Aggarwal MM Ahammed Z Angelis AL Antonenko V Arefiev V Astakhov V Avdeitchikov V Awes TC Baba PV Badyal SK Bathe S Batiounia B Baumann C Bernier T Bhalla KB Bhatia VS Blume C Bucher D Büsching H Carlén L Chattopadhyay S Decowski MP Delagrange H Donni P Majumdar MR El Chenawi K Dubey AK Enosawa K Fokin S Frolov V Ganti MS Garpman S Gavrishchuk O Geurts FJ Ghosh TK Glasow R Guskov B Gustafsson HA Gutbrod HH Hrivnacova I Ippolitov M Kalechofsky H Kamermans R Karadjev K Karpio K Kolb BW Kosarev I 《Physical review letters》2008,100(24):242301
Neutral pion transverse momentum spectra were measured in p+C and p+Pb collisions at sqrt[S{NN}]=17.4 GeV at midrapidity (2.3 less than or approximately equal eta{lab} less than or approximately equal 3.0) over the range 0.7 less than or approximately equal p{T} less than or approximately equal 3.5 GeV/c. The spectra are compared to pi{0} spectra measured in Pb+Pb collisions at sqrt[S{NN}]=17.3 GeV in the same experiment. For a wide range of Pb+Pb centralities (N{part} less than or approximately equal 300), the yield of pi{0}'s with p{T} greater than or approximately equal 2 GeV/c is larger than or consistent with the p+C or p+Pb yields scaled with the number of nucleon-nucleon collisions (N{coll}), while for central Pb+Pb collisions with N{part}greater than or approximately equal 350, the pi{0} yield is suppressed. 相似文献
13.
I.G. Bearden H. Bøggild J. Boissevain P.H.L. Christiansen L. Conin J. Dodd B. Erazmus S. Esumi C.W. Fabjan D. Ferenc A. Franz J.J. Gaardhøje A.G. Hansen O. Hansen D. Hardtke H. van Hecke E.B. Holzer T.J. Humanic P. Hummel B.V. Jacak K. Kaimi M. Kaneta T. Kohama M. Kopytine M. Leltchouk A. Ljubičić Jr. B. Lörstad N. Maeda L. Martin A. Medvedev M. Murray H. Ohnishi G. Paić S.U. Pandey F. Piuz J. Pluta V. Polychronakos M. Potekhin G. Poulard D. Reichhold A. Sakaguchi J. Schmidt-Sørensen J. Simon-Gillo W. Sondheim T. Sugitate J.P. Sullivan Y. Sumi W.J. Willis K. Wolf N. Xu D.S. Zachary 《The European Physical Journal C - Particles and Fields》2000,18(2):317-325
Two-particle correlations of negative pions as a function of charged particle multiplicity are studied in Pb+Pb collisions
at GeV per nucleon using the NA44 experiment at the CERN Super Proton Synchrotron(SPS). We find that the source size parameters
increase with the charged particle multiplicity. However the slope of the source size parameters plotted as a function of
charged multiplicity is slightly larger at high multiplicity than at low multiplicity. The value of is independent of charged multiplicity. For Pb+Pb collisions, is larger than and for all multiplicity intervals, whereas these three radius parameters were approximately equal in S+Nucleus collisions. The
ratios () and () for Pb+Pb data show almost no dependence on charged multiplicity. The duration of pion emission is constant at 3.81.1 fm/c as a function of the charged multiplicity in Pb+Pb collisions. Effective volume (V) is also calculated as V=, assuming a cylindrically shaped source. We found, within the limited statistics, the effective volume rapidly increases
at high multiplicity.
Received: 17 July 2000 / Revised version: 3 November 2000 / Published online: 8 December 2000 相似文献
14.
B. Hippolyte 《The European Physical Journal C - Particles and Fields》2007,49(1):121-124
Strange quark and hadron production will be studied at the large hadron collider (LHC) energies in order to explore the properties
of both pp and heavy-ion collisions. The ALICE experiment will be specifically efficient in the strange sector with the identification
of baryons and mesons over a wide range of transverse momentum. Dedicated measurements are proposed for investigating chemical
equilibration and bulk properties. Strange particles can also help to probe kinematical regions where hard processes and pQCD
dominate. We try to anticipate here several ALICE analyses to be performed as the first Pb–Pb and pp data will be available.
PACS 25.75.-q; 25.75.Dw 相似文献
15.
J. Mercado 《Physics of Particles and Nuclei Letters》2011,8(9):885-887
ALICE is the experiment at the CERN Large Hadron Collider dedicated to study high-energy nuclear collisions which is also
carrying out a proton-proton physics program, thanks to its wide phase-space coverage and good momentum and spatial resolution.
We present first results on two-pion Bose-Einstein correlations in pp collisions at √s = 900 GeV measured with ALICE. An increase of the HBT radius with increasing event multiplicity is observed, in agreement
with previous measurements. However, a strong decrease of the radius with increasing transverse momentum, as observed at RHIC
and at Tevatron, is not evident in our analysis. 相似文献
16.
In the Color Glass Condensate formalism, charged hadron p T spectra in p+p and p+Pb collisions are studied by considering an energy-dependent broadening of nucleon density distribution. Then, in the glasma flux tube picture, the n-particle multiplicity distributions at different pseudo-rapidity ranges are investigated. Both the theoretical results show good agreement with the recent experimental data from ALICE and CMS at LHC energies.The predictive results for p T or multiplicity distributions in p+p and p+Pb collisions at the Large Hadron Collider are also given in this paper. 相似文献
17.
Bearden IG Bøggild H Boissevain J Christiansen PH Conin L Dodd J Erazmus B Esumi S Fabjan CW Ferenc D Franz A Gaardhøje JJ Hansen AG Hansen O Hardtke D van Hecke H Holzer EB Humanic TJ Hummel P Jacak BV Kaimi K Kaneta M Kohama T Kopytine M Leltchouk M Ljubicic A Lörstad B Maeda N Martin L Medvedev A Murray M Ohnishi H Paic G Pandey SU Piuz F Pluta J Polychronakos V Potekhin M Poulard G Reichhold D Sakaguchi A Schmidt-Sørensen J Simon-Gillo J Sondheim W Sugitate T Sullivan JP Sumi Y Willis WJ 《Physical review letters》2001,87(11):112301
Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta
approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity. 相似文献
18.
《中国科学:物理学 力学 天文学(英文版)》2016,(3)
The time evolution of both proton and anti-proton v_2 flows from Au+Au collisions at (S_NN)~(1/2)=7.7 Ge V are examined by using both pure cascade and mean-field potential versions of the Ur QMD model. Due to a stronger repulsion at the early stage introduced by the repulsive potentials and hence much less annihilation probabilities, anti-protons are frozen out earlier with smaller v_2 values.Therefore, the experimental data of anti-proton v_2 as well as the flow difference between proton and anti-proton can be reasonably described with the potential version of UrQMD. 相似文献
19.
The shower shape of n,n,p,p,K+,π+ and photons,generated by JPCIAE code for 5.5 TeV/A 208Pb+208Pb collisions,incident on the ALICE photon spectrometer(PHOS),is analyzed with the principal component analysis(PCA) method.The efficiency dependence of purity for the photon discrimination is simulated for the deposited energy ranges 0.5-2 GeV,2-10 GeV,10-50 GeV and 50-100 GeV.The result shows that in the energy range of 0.5 to 100 GeV,the efficiency of the photon identification can reach 90% with purity of 90%. 相似文献
20.
We present a systematic analysis of two-pion interferometry for the central Au+Au collisions at √sNN=3, 5, 7, 11, 17, 27, 39, 62, 130 and 200 GeV/c with the help of a multiphase transport (AMPT) model. Emission source-size radius parameters Rlong, Rout, Rside and the chaotic parameter λ are extracted and compared with the experimental data. Transverse momentum and azimuthal angle dependencies of the HBT radii are also discussed for central Au+Au collisions at 200 GeV/c. The results show that the HBT radii in central collisions do not change much above 7 GeV/c. For central collisions at 200 GeV/c, the radii decrease with the increasing of transverse momentum pT but are not sensitive to the azimuthal angle. These results provide a theoretical reference for the energy scan program of the RHIC-STAR experiment. 相似文献