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Recently, the rapidity-odd directed flow ( v 1 ) of produced hadrons ( K − , ϕ , p ¯ , Λ ¯ , Ξ ¯ + , Ω − , and Ω ¯ + ) has been studied. Several combinations of these produced hadrons, with very small mass differences but differences in the net electric charge ( Δ q ) and net strangeness ( Δ S ) on the two sides, have been considered. A difference in v 1 between the two sides of these combinations ( Δ v 1 ) has been proposed as a consequence of the electromagnetic field produced in relativistic heavy-ion collisions, especially if Δ v 1 increases with Δ q . Our study is performed to understand the effect of the coalescence sum rule (CSR) on Δ v 1 . We point out that the CSR leads to Δ v 1 = c q Δ q + c S Δ S , where the coefficients c q and c S reflect the Δ v 1 of produced quarks. Equivalently, one can write Δ v 1 = c q Δ q + c B Δ B , involving the difference in the net baryon number Δ B , where the CSR gives c B = − 3 c S . We then propose two methods to extract the coefficients for the Δ q and Δ S dependences of Δ v 1 . [ABSTRACT FROM AUTHOR]

The shear viscosity η of a quark–gluon plasma in equilibrium can be calculated analytically using multiple methods or numerically using the Green–Kubo relation. It has been realized, which we confirm here, that the Chapman–Enskog method agrees well with the Green–Kubo result for both isotropic and anisotropic two-body scatterings. We then apply the Chapman–Enskog method to study the shear viscosity of the parton matter from a multi-phase transport model. In particular, we study the parton matter in the center cell of central and midcentral Au + Au collisions at 200A GeV and Pb + Pb collisions at 2760A GeV, which is assumed to be a plasma in thermal equilibrium but partial chemical equilibrium. As a result of using a constant Debye mass or cross section σ for parton scatterings, the η / s ratio increases with time (as the effective temperature decreases), contrary to the trend preferred by Bayesian analysis of the experimental data or pQCD results that use temperature-dependent Debye masses. At σ = 3 mb that enables the transport model to approximately reproduce the elliptic flow data of the bulk matter, the average η / s of the parton matter in partial equilibrium is found to be very small, between one to two times 1 / (4 π) . [ABSTRACT FROM AUTHOR]

Predictions made in Albacete et al. [ Int. J. Mod. Phys. E 22 (2013) 1330007] prior to the LHC Pb run at TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication. [ABSTRACT FROM AUTHOR]

We have studied the K* production within a multi-phase transport model (AMPT) for + collisions at to understand the hadronic re-scattering effect on the measured yields of the resonance. The hadronic re-scattering of the K* decay daughter particles (π and K) will alter their momentum distribution thereby making it difficult to reconstruct the K* signal through the invariant mass method. An increased hadronic re-scattering effect thus leads to a decrease in the reconstructed yield of K* in the heavy-ion collisions. Through this simulation study, we argue that a decrease in K*/K ratio with the increase in collision centrality necessarily reflects the hadronic re-scattering effect. Since the re-scattering occurs in the hadronic phase and K* has a lifetime of 4 fm/c, we present a toy model-based discussion on using measured K*/K to put a lower limit on the hadronic phase lifetime in high energy nuclear collisions. [ABSTRACT FROM AUTHOR]

Using a multiphase transport model, we study the production of multistrange (anti)baryons from the hadronic matter formed in relativistic heavy ion collisions. The mechanism we introduce is the strangeness-exchange reactions between antikaons and hyperons for strange particle production and between kaons and antihyperons for strange antiparticle production. We find that these reactions contribute significantly to the production of multistrange baryons and antibaryons in heavy ion collisions at SPS energies, which has been found to be appreciably enhanced. We have also made predictions for multistrange baryon and antibaryon production in heavy ion collisions at RHIC and found a similar enhancement. The (anti)particle mass dependence of inverse slope parameters extracted from their transverse mass spectra in the transport model exhibit similar trend as in the available experimental data at both SPS and RHIC energies. [Copyright &y& Elsevier]