Dynamical initial-state model for relativistic heavy-ion collisions

Abstract

We present a fully three-dimensional model providing initial conditions for energy and net-baryon density distributions in heavy ion collisions at arbitrary collision energy. The model includes the dynamical deceleration of participating nucleons or valence quarks, depending on the implementation. The duration of the deceleration continues until the string spanned between colliding participants is assumed to thermalize, which is either after a fixed proper time, or a fluctuating time depending on sampled final rapidities. Energy is deposited in space-time along the string, which in general will span a range of space-time rapidities and proper times. We study various observables obtained directly from the initial state model, including net-baryon rapidity distributions, 2-particle rapidity correlations, as well as the rapidity decorrelation of the transverse geometry. Their dependence on the model implementation and parameter values is investigated. We also present the implementation of the model with 3+1 dimensional hydrodynamics, which involves the addition of source terms that deposit energy and net-baryon densities produced by the initial state model at proper times greater than the initial time for the hydrodynamic simulation.

Unified description of hadron yield ratios from dynamical core-corona initialization

“…1 Under this framework, the initial condition of the QGP fluids is obtained via energy-momentum deposition from the partons/strings/fields generated just after the collision. As extension of the dynamical initialization description for QGP fluids generation from initially produced partons [47][48][49][50], we introduced the dependence on initial parton densities in the dynamical initialization [50], which we call the "dynamical core-corona initialization (DCCI) model" in this paper. Given the various definitions of the core and the corona in the literature [41][42][43][44][45][46], we here define them explicitly as follows: The core represents the fluids under local thermal and chemical equilibrium, while the corona represents the system composed of non-equilibrated partons traversing the fluids or the vacuum.…”

Equilibration and baryon densities attainable in relativistic heavy-ion collisions

“…The main part of the hydro models [17][18][19][20][21][22][23], that are designed for describing evolution of the baryon-rich matter, takes their initial conditions from third-party kinetic codes. Unlike those hybrid hydro models, the 3FD model [12] takes into account finite stopping power of nuclear matter right within the 3FD evolution.…”

“…Thus, the 3FD approximation is a minimal way to simulate the earlystage nonequilibrium at high collision energies. Similar concepts were used in recently developed hybrid models [20][21][22][23]. Unlike the 3FD, these hybrid models deal with a single equilibrated fluid that however does not involve all the matter of colliding nuclei.…”

Rapidity decorrelation from hydrodynamic fluctuations

“…To separate the effects of these two decorrelations, the factorization ratios are defined in different ways [51,55]. These factorization ratios are studied in various models with the effects of initial twists [55,56], longitudinal fluctuations [57][58][59][60][61][62], glasma [63], and dynamical initial states [64]. The factorization ratios can be reasonably described by the effects of initial twists [55].…”