Dilepton production in schematic causal viscous hydrodynamics

Abstract

Assuming that in the hot dense matter produced in relativistic heavy-ion collisions, the energy density, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform in the direction transversal to the reaction plane, we derive a set of schematic equations from the Isreal-Stewart causal viscous hydrodynamics. These equations are then used to describe the evolution dynamics of relativistic heavy-ion collisions by taking the shear viscosity to entropy density ratio of 1/4π for the initial quark-gluon plasma (QGP) phase and of ten times this value for the later hadron-gas (HG) phase. Using the production rate evaluated with particle distributions that take into account the viscous effect, we study dilepton production in central heavy-ion collisions. Compared with results from the ideal hydrodynamics, we find that although the dilepton invariant mass spectra from the two approaches are similar, the transverse momentum spectra are significantly enhanced at high transverse momenta by the viscous effect. We also study the transverse momentum dependence of dileptons produced from QGP for a fixed transverse mass which is essentially absent in the ideal hydrodynamics, and find that this so-called transverse mass scaling is violated in the viscous hydrodynamics, particularly at high transverse momenta.

Charmonium production in relativistic heavy-ion collisions

“…The initial thermalization time is taken to be 1.0 fm/c for SPS, which has usually been used, and 0.9 fm/c and 1.05 fm/c for RHIC and LHC, respectively [43]. Although the initial thermalization time for RHIC is 0.6 fm/c in ideal hydrodynamics [45], the nonzero viscosity generates additional transverse flow [23] and requires a late thermalization to fit the experimental data on p T spectra and elliptic flows. This is the same reason for the later thermalization at LHC in viscous hydrodynamics.…”

“…The cold nuclear matter effects include the Cronin effect of gluon-nucleon scattering before the production of the primordial J/ψ from the gluon-gluon fusion [18]; the shadowing effect due to the modification of the gluon distribution in a heavy nucleus [19]; and the nuclear absorption by the passing nucleons [20][21][22]. In our previous work [23] on J/ψ production in heavy-ion collisions at RHIC, we have considered only the most important nuclear absorption effect. In this case, the survival probability of a primordial J/ψ after the nuclear absorption is given by [24,25] …”

“…[23]. It is based on the assumption that all thermal quantities such as the energy density, temperature, entropy density, and pressure as well as the azimuthal and space-time rapidity components of the shear tensor are uniform along the transverse direction in the hot dense matter.…”

Bottomonia suppression in relativistic heavy-ion collisions

“…Since the suggestion by Matsui and Satz [1] that suppressed production of J/ψ in relativistic heavy-ion collisions could be a signature for produced QGP, there have been many experimental [2,3] and theoretical studies [4][5][6][7][8][9][10][11] on this very interesting phenomenon; see, e.g., Refs. [12,13] for a recent review.…”

Parity and time-reversal violation in A=2-4 nuclei

“…Parity violating effects, including neutron spin rotation and the longitudinal asymmetry, for n-p and n-d elastic scattering have been also carried out using hybrid model, i.e. combining realistic strong interaction Hamiltonians with pionless and pionic EFT weak currents in [24]. Lately, parity violation has also been explored for the case of neutron-deuteron radiative capture [25].…”