共查询到20条相似文献,搜索用时 15 毫秒
1.
We predict the transverse momentum (p(T)) dependence of elliptic flow of thermal photons for Au + Au collisions at the BNL Relativistic Heavy Ion Collider. We model the system hydrodynamically, with a thermalized quark-gluon plasma at early times followed by hadronization and decoupling. Photons are emitted throughout the expansion history. Contrary to hadron elliptic flow, which increases monotonically with p(T), the elliptic flow nu2(p(T)) of thermal photons is predicted to first rise and then fall again. Photon elliptic flow at high p(T) reflects the quark momentum anisotropy at early times when it is small, while at low p(T) it mirrors the large pion momentum anisotropy during the late hadronic emission stage. An interesting structure is predicted at intermediate p(T) approximately 0.4 GeV/c, where photon elliptic flow reflects the momenta and the (compared to pions) reduced nu2 of heavy vector mesons in the late hadronic phase. 相似文献
2.
We show that hadronization via quark coalescence enhances hadron elliptic flow at large p(perpendicular) relative to that of partons at the same transverse momentum. Therefore, compared to earlier results based on covariant parton transport theory, more moderate initial parton densities dN/deta(b=0) approximately 1500-3000 can explain the differential elliptic flow v(2)(p(perpendicular)) data for Au+Au reactions at sqrt[s]=130 and 200A GeV from BNL RHIC. In addition, v(2)(p(perpendicular)) could saturate at about 50% higher values for baryons than for mesons. If strange quarks have weaker flow than light quarks, hadron v(2) at high p(perpendicular) decreases with relative strangeness content. 相似文献
3.
H. Petersen J. Steinheimer Gerhard Burau Marcus Bleicher 《The European Physical Journal C - Particles and Fields》2009,62(1):31-36
The elliptic flow excitation function calculated in a Boltzmann approach with an intermediate hydrodynamic stage for heavy-ion
reactions from GSI-SIS to the highest CERN-SPS energies is discussed in the context of the experimental data. The specific
setup with initial conditions and freeze-out from a non-equilibrium transport model allows for a direct comparison between
ideal fluid dynamics and hadronic transport simulations. At higher SPS energies, where the pure transport calculation cannot
account for the high elliptic flow values, the smaller mean free path in the hydrodynamic evolution leads to higher elliptic
flow values. The lower mean free path leads to higher pressure gradients in the early stage and as a consequence to higher
elliptic flow values even without a phase transition. Special emphasis is put on the influence of the initial conditions on
the results of the hybrid model calculation. Event-by-event fluctuations are directly taken into account via event-wise non-equilibrium
initial conditions generated by the primary collisions and string fragmentations in the microscopic UrQMD model. This leads
to non-trivial velocity and energy density distributions for the hydrodynamical initial conditions. Due to the more realistic
initial conditions and the incorporated hadronic rescattering the results are in line with the experimental data almost over
the whole energy range from E
lab=2–160A GeV. 相似文献
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Produced partons have a large local relative orbital angular momentum along the direction opposite to the reaction plane in the early stage of noncentral heavy-ion collisions. Parton scattering is shown to polarize quarks along the same direction due to spin-orbital coupling. Such global quark polarization will lead to many observable consequences, such as left-right asymmetry of hadron spectra and global transverse polarization of thermal photons, dileptons, and hadrons. Hadrons from the decay of polarized resonances will have an azimuthal asymmetry similar to the elliptic flow. Global hyperon polarization is studied within different hadronization scenarios and can be easily tested. 相似文献
7.
We construct the spaces that the elliptic Ruijsenaars operators act on. It is shown that they are extensible to nonnegative selfadjoint operators on a space of square integrable functions, or preserve a finite dimensional vector space of entire functions. These facts are shown in terms of the R-operators which satisfy the Yang–lBaxter equation. The elliptic Ruijsenaars operators are considered as the elliptic analogues of the Macdonald operators or the difference analogues of the Lamé operators. 相似文献
8.
Bin Zhang 《The European Physical Journal C - Particles and Fields》2009,62(1):25-29
The parton-cascade model is a microscopic transport approach in the study of the space-time evolution of the quark–gluon plasma
produced in relativistic heavy-ion collisions and its experimental manifestations. In the following, parton-cascade calculations
on elliptic flow and thermalization will be discussed. Dynamical evolution is shown to be important for the production of
elliptic flow including the scaling and the breaking of the scaling of elliptic flow. The degree of thermalization is estimated
using both an elastic parton-cascade and a radiative transport model. A longitudinal to transverse pressure ratio of P
L
/P
T
≈0.8 is shown to be expected in the central cell in central collisions. This provides information on viscous corrections to
the ideal hydrodynamical approach. 相似文献
9.
S.J.Sanders 《中国物理 C》2007,31(12):1137-1140
Identified particle elliptic flow results are presented for the Au+Au reaction at sNN=200GeV as a function of transverse momentum and pseudorapidity. Data at pseudorapidities η≈0,1, and 3.4 were obtained using the two BRAHMS spectrometers. Differential v2 (η,pt) values for a given particle type are
found to be essentially constant over the covered pseudorapidity range, in contrast to the integral v2 values which have previously been observed to decrease at forward rapidities. A softening of the particle spectra at forward angles is found to account for at least part of the integral v2 falloff. The data are found to be consistent with existing constituent quark scaling systematics. 相似文献
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W.M. Alberico P. Czerski M. Nardi 《The European Physical Journal A - Hadrons and Nuclei》1999,4(2):195-203
We present a three–dimensional model for quark matter with a density dependent quark–quark (confining) potential, which allows
to describe a sort of deconfinement transition as the system evolves from a low density assembly of bound structures to a
high density free Fermi gas of quarks. We consider different confining potentials, some of which successfully utilized in
hadron spectroscopy. We find that a proper treatment of the many–body correlations induced by the medium is essential to disentangle
the different nature of the two (hadronic and deconfined) phases of the system. For this purpose the ground state energy per
particle and the pair correlation function are investigated.
Received: 10 June 1998 / Revised version: 24 September 1998 相似文献
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Hadron Multiplicities in Pb+Pb Collisions at the Large Hadron Collider and Pomeron Loop Effects 下载免费PDF全文
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
14.
Harry J. Lipkin 《Zeitschrift für Physik A Hadrons and Nuclei》1967,202(1):414-424
The expressions for total scattering cross sections obtained from the quark model are expressed in a simple form which shows the dependence of the results on the assumptions. The results are shown to depend only on the value of six constants or “charges” defined for each hadron and to be otherwise independent of the structure. Any model which gives the same values of these charges gives the same result as the quark model. In particular, the results for processes which have odd signature t-channel quantum numbers hold in a quark model even with arbitrary mixtures of additional quarkantiquark pairs in the hadron wave function, provided that B, Y, and I are conserved. 相似文献
15.
Dirk H. Rischke Yariş Pürsün Joachim A. Maruhn Horst Stöcker Walter Greiner 《Acta Physica Hungarica A》1995,1(3-4):309-322
It is shown that in ideal relativistic hydrodynamics a phase transition from hadron to quark and gluon degrees of freedom in the nuclear matter equation of state leads to a minimum in the excitation function of the transverse collective flow. 相似文献
16.
M. Csanád T. Csörgő A. Ster B. Lörstad N. N. Ajitanand J. M. Alexander P. Chung W. G. Holzmann M. Issah R. A. Lacey 《The European Physical Journal A - Hadrons and Nuclei》2008,38(3):363-368
Recent PHOBOS measurements of the excitation function for the pseudo-rapidity dependence of the elliptic flow in Au + Au collisions
at RHIC have posed a significant theoretical challenge. Here we show that these differential measurements, as well as the
RHIC measurements on transverse momentum satisfy a universal scaling relation predicted by the Buda-Lund model, based on exact
solutions of perfect fluid hydrodynamics. We also show that the recently found transverse kinetic energy scaling of the elliptic
flow is a special case of this universal scaling. 相似文献
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18.
Yoshimasa Ikeda 《Central European Journal of Physics》2012,10(6):1311-1313
Measurement of azimuthal anisotropy is one of the most important study because of its relation to the initial stage. Especially, the elliptical anisotropy which is measured as the second coefficient of Fourier expansion of particle azimuthal distribution is believed to carry the information about the initial geometrical anisotropy. It seems the identified hadron v 2 depends on the number of quark contents of the hadron. The experimental result of quark number scaling of v 2 suggests quark level collectivity in the hot dense matter and quark coalescence mechanism to form hadron from quark matter via quark-gluon phase transition. The measured v 2 and p T spectra are analyzed with various assumptions based on the blast wave model in order to understand the freeze-out temperature and collective flow after the system expansion. 相似文献
19.
提出一种新的包含三代已知轻子与夸克的SU(5)大统—模型.按本模型,强子可看作由夸克形成的非拓扑孤粒子;轻子与夸克本质上是相同的,它们之间的差别是由对称性自发破缺造成的;在强子内部,夸克质量很小,其性质与已知夸克相同;在强子外部,夸克的性质与已知轻子相同,只是质量很重,并将很快衰变.本文除了定义严格守恒的电荷Q0、费米子数F0外,还在孤粒子内部定义了近似守恒的内色荷、内电荷、内费米子数.已知SU(5)大统—模型的(L-B)守恒相应于本模型的F0守恒。 相似文献