Yuanfang Wu

Erraticity analysis of multiparticle production in π+p and K+p collisions at 250 GeV/c

Abstract The erraticity behavior of multiparticle production is analyzed in π + p and K + p collisions at 250 GeV/ c . It is demonstrated that, for these low-multiplicity final states, the erraticity measure based on event-to-event fluctuation of factorial moments is dominated by statistical fluctuations.

The study of non-collectivity by the forward–backward multiplicity correlation function

We propose a forward–backward multiplicity correlation function CNFB, which is experimentally accessible, to measure the non-collectivity contribution. It is found that the function is sensitive to both the jet contribution and small number statistics. We point out that the effect of the latter is also involved in the previous studies of the forward–backward elliptic correlation function but was misinterpreted as a contribution from jets. We study the CNFB in Au+Au collision at GeV with a multiphase transport model (AMPT). The result shows that the estimated jet contribution is much smaller than in the previous study due to the finite number statistics which has not been noticed before. The connection between this study and the forward–backward elliptic correlation function is also discussed.

Boost invariance and multiplicity dependence of the charge balance function in π+p and K+p collisions at s=22 GeV

Abstract Boost invariance and multiplicity dependence of the charge balance function are studied in π + p and K + p collisions at 250 GeV/ c incident beam momentum with full acceptance coverage. Charge balance, as well as charge fluctuations, are found to be boost invariant over the whole rapidity region, but both depend on the size of the rapidity window. It is also found that the balance function becomes narrower with increasing multiplicity, which is consistent with the narrowing of the balance function with increasing centrality and/or system size, as observed in current relativistic heavy ion experiments.

Influences of statistics and initial size fluctuation on high-order cumulants of conserved quantities in relativistic heavy ion collisions

Through the generation of the UrQMD model, event statistics for the products of kurtosis (κ) and variance (σ2) of net-proton and net-charge multiplicity distributions are carefully studied. It is shown that the statistics at RHIC/BES at GeV are not sufficient to use the method of centrality bin width correction (CBWC). Corresponding results are systematically underestimated. A way to improve the CBWC method is proposed. It can remove the statistical dependence of the data and also reduce the initial size fluctuation.

Influence of statistics on the measured moments of conserved quantities in relativistic heavy ion collisions

We study statistics dependence of the probability distributions and the means of measured moments of conserved quantities, respectively. The required statistics of all interested moments and their products are estimated based on a simple simulation. We also explain why the measured moments are underestimated when the statistics are insufficient.With the statistics at RHIC/BES, the second and third order moments can be reliably obtained based on the method of Centrality bin width correction (CBWC), which can not be applied for the fourth order moments at low energy. With planning statistics at RHIC/BES II, and improved CBWC method,

Statistical and dynamical fluctuations in the ratios of higher net-proton cumulants in relativistic heavy-ion collisions

\kappa\sigma^2

Longitudinal boost invariance of the charge balance function in hadron-hadron and nucleus-nucleus collisions

in a finer centrality bin scale should be measurable. This will help us to understand the current observation of energy and centrality dependence of high-order moments.

An explorer for the shear viscosity in the formed matter at the RHIC

With the help of transport and statistical models, we find that the ratios of higher net-proton cumulants measured at RHIC are dominated by Poisson-like statistical fluctuations. A way to eliminate this statistical fluctuation is suggested. The obtained dynamical ratios of higher net-proton cumulants are demonstrated to be more relevant to the underlying physics, i.e. the correlations between proton and antiproton, or the critical fluctuations.

EVENT-BY-EVENT FLUCTUATIONS OF TRANSVERSE MOMENTUM IN ELEMENTARY COLLISIONS AT 250 GEV/C

Using Monte Carlo generators of the PYTHIA model for hadron-hadron collisions and a multiphase transport (AMPT) model for nucleus-nucleus collisions, the longitudinal boost-invariance of charge balance function and its transverse momentum dependence are carefully studied. It shows that the charge balance function is boost-invariant in both p+p and Au+Au collisions in these two models, consistent with experimental data. The balance function properly scaled by the width of the pseudorapidity window is independent of the position or the size of the window and is corresponding to the balance function of the whole pseudorapidity range. This longitudinal property of balance function also holds for particles in small transverse momentum ranges in the PYTHIA and the AMPT default models, but is violated in the AMPT with string melting. The physical origin of the results are discussed.

Statistical and dynamical parts of the cumulants of conserved charges in relativistic heavy ion collisions

The neighboring azimuthal bin–bin multiplicity correlation pattern is suggested. It is demonstrated to be a good measure for internal interaction of the formed matter at the RHIC. The relation between the correlation pattern and shear viscosity is derived. As an example, the shear viscosity in the sample generated by AMPT with string melting is estimated.