Huo Lei

Eccentricity Scaling of Elliptic Flow in Relativistic Au+Au Collisions

Elliptic flow for Au+Au non-central collisions at = 200 GeV is investigated within a (2+1)-dimensional hydrodynamic model. The results show that the eccentricity scaling for the collisions is almost perfect. The evolution including the phase transition conforms to the demand of scaling invariance of hydrodynamics of the collision system.

Semiclassical Model of Quark-Gluon Plasma

A semiclassical model of a gluon—quark plasma (QGP) is provided. The spinof the quark is described by an antisymmetric tensor Sμν and color charges,and spin tensor are defined as semiclassical numbers. The transport propertiesof QGP in color space and spin space are investigated. The consistency of thesemiclassical model and the quantum models of QGP is discussed.

The Evolution of Elliptic Flow Under First Order Phase Transition

Elliptic flow for non-central Au+Au collisions at √(sNN) = 200 GeV is investigated with a 2+1 dimensional hydrodynamic model. We analyze the softening effect by the velocity along the axis. The contribution of the elliptic flow from the QGP phase, mixed phase and hadron gas phase is studied. The relation between the sound horizon and evolution of the elliptic flow is discussed.

Comment on phase conventions in helicity formalism

Using the sequential decay process , Λ → pπ−, as an example, the procedure for deducing the full angular distribution is illustrated by adopting both the Jacob-Wick and Jackson conventions in the helicity formalism. To make sure that the final physical result is free of phase conventions, we point out that the coefficients that relate the angular momentum states in different coordinate systems of reference frames have to be taken into account properly in the procedure. The fact that those coefficients are constants suggests that the Jackson convention is favorable in dealing with the processes with sequential decays.

A viable method for goodness-of-fit test in maximum likelihood fit

A test statistic is proposed to perform the goodness-of-fit test in the unbinned maximum likelihood fit. Without using a detailed expression of the efficiency function, the test statistic is found to be strongly correlated with the maximum likelihood function if the efficiency function varies smoothly. We point out that the correlation coefficient can be estimated by the Monte Carlo technique. With the established method, two examples are given to illustrate the performance of the test statistic.

Prospects on Determining Electric Dipole Moments of Σ and Ξ Hyperons at BESIII

The electric dipole moment of Σ (or Ξ hyperon, dΣ (or dΞ), can be detected by analyzing the angular distribution in the decay process of . The dependence of dΣ (or dΞ) on the free parameters describing the angular distribution is studied in detail with a Monte Carlo simulation based on 109 J/Ψ events expected in one year data taking at BESIII. The result shows that an expected upper limit with 10−16 ~ 10−18 e cm on dΣ (or dΞ) can be achieved depending on the true values of free parameters.

Space-momentum correlations in 8 AGeV Au+Au collisions

Within the RQMD model, space-momentum correlations, i.e. the correlations between final momentum anisotropy and initial eccentricity, are studied for 8 AGeV Au+Au events classified according to the multi-particle azimuthal correlations. The results show that the final elliptic flow fluctuations depend on the initial collision geometry. There are clear space-momentum correlations for nucleons during the whole dynamical evolution of the collisions.

A Non-Zero Hadronic Elliptic Flow with a Vanished Partonic Elliptic Flow in a Coalescence Scenario

The elliptic flow of a hadron is calculated using a quark coalescence model based on the quark phase space distribution produced by a free streaming locally thermalized quark in a two-dimensional transverse plane at initial time. Without assuming the quarks elliptic flow, it is shown that the hadron obtains a non-zero elliptic flow in this model. The elliptic flow of the hadron is shown to be sensitive to both space momentum correlation and the hadrons internal structure. Quark number scaling is obtained only for some special cases.

Size of the freeze-out source in high energy heavy ion collisions

Based on a hydro-inspired azimuthally symmetric emission function, we analyze the HBT radius RS and the single-particle transverse momentum spectra in Au+Au collisions measured by the STAR Collaboration at GeV. The results show that consistent assumptions about transverse density (and/or flow profile) in the calculation of the HBT radius RS and single-particle spectral analyses play an important role for understanding the size of the freeze-out source.

Effects of Surface Emitting and Cumulative Collisions on Elliptic Flow

The integral and differential elliptic flow of partons is calculated using the multiphase transport model for Au+Au collisions at centre-of-mass energy = 200 GeV. It is shown that elliptic flow of partons freezing out at early time, which is affected mainly by surface emittance, decreases with time and elliptic flow of partons freezing out at late time, which is dominated by cumulative collisions, increases with time. The elliptic flow of partons freezing out early has a large contribution to the flatting of curve of final differential elliptic flow at large transverse momentum. It is argued that the effect of surface emittance is not neglectable.