Heavy ion event generator HYDJET++ (HYDrodynamics plus JETs)

Abstract

HYDJET++ is a Monte-Carlo event generator for simulation of relativistic heavy ion AA collisions considered as a superposition of the soft, hydro-type state and the hard state resulting from multi-parton fragmentation. This model is the development and continuation of HYDJET event generator (Lokhtin & Snigirev, 2006, EPJC, 45, 211). The main program is written in the object-oriented C++ language under the ROOT environment. The hard part of HYDJET++ is identical to the hard part of Fortran-written HYDJET and it is included in the generator structure as a separate directory. The soft part of HYDJET++ event is the "thermal" hadronic state generated on the chemical and thermal freeze-out hypersurfaces obtained from the parameterization of relativistic hydrodynamics with preset freezeout conditions. It includes the longitudinal, radial and elliptic flow effects and the decays of hadronic resonances. The corresponding fast Monte-Carlo simulation procedure, C++ code FAST MC (Amelin et al., 2006, PRC, 74, 064901; 2008, PRC, 77, 014903) is adapted to HYDJET++. It is designed for studying the multi-particle production in a wide energy range of heavy ion experimental facilities: from FAIR and NICA to RHIC and LHC. PACS: 24.10.Lx, 24.85.+p, 25.75.Bh, 25.75.Dw, 25.75.Ld, 25.75 RAM: 50 MBytes (determined by ROOT requirements)Number of processors used: 1 Keywords: Monte-Carlo event generators, relativistic heavy ion collisions, hydrodynamics, QCD jets, partonic energy loss, flow, quark-gluon plasma PACS: 24.10. Lx, 24.85.+p, 25.75.Bh, 25.75.Dw, 25.75.Ld, 25.75.Nq Classification: 11.2 Elementary particle physics, phase space and event simulation External routines/libraries: ROOT (any version)Subprograms used: PYTHIA event generator (version 6.401 or later), PYQUEN event generator (version 1.5 or later) Nature of the physical problem:The experimental and phenomenological study of multi-particle production in relativistic heavy ion collisions is expected to provide valuable information on the dynamical behaviour of strongly-interacting matter in the form of quark-gluon plasma (QGP) [2][3][4], as predicted by lattice Quantum Chromodynamics (QCD) calculations. Ongoing and future experimental studies in a wide range of heavy ion beam energies require the development of new Monte-Carlo (MC) event generators and improvement of existing ones. Especially for experiments at the CERN Large Hadron Collider (LHC), implying very high parton and hadron multiplicities, one needs 2 fast (but realistic) MC tools for heavy ion event simulations [5][6][7]. The main advantage of MC technique for the simulation of high-multiplicity hadroproduction is that it allows a visual comparison of theory and data, including if necessary the detailed detector acceptances, responses and resolutions. The realistic MC event generator has to include maximum possible number of observable physical effects, which are important to determine the event topology: from the bulk properties of soft hadroproduction (domain of low transverse momenta p T < ∼ 1G...

The radiation pattern of a QCD antenna in a dense medium

“…The medium-induced single-inclusive spectrum off a single charge, known henceforth as the BDMPS-Z spectrum, serves also as a building block for treating multigluon emissions, see, e.g., [31,32]. These ad hoc extensions can therefore only account for uncorrelated emissions (except for trivial correlations such as energy-momentum conservation) and serve as working models for phenomenological applications and Monte-Carlo implementations, e.g., [33][34][35][36].…”

Transverse momentum distribution and elliptic flow of charged hadrons in $$U+U$$ U + U collisions at $$\sqrt{s_{NN}}=193$$ s NN = 193 GeV using HYDJET++

“…The soft and hard components are treated independently in HYDJET++. The details on physics model and simulation procedure of HYDJET++ can be found in the corresponding manual [28,29]. The main features of HYDJET++ model are listed very briefly in this section.…”

“…The model for the hard multi-parton production of HYD-JET++ event is based on PYQUEN partonic loss model [30][31][32]. In brief the hard part of hadron production in HYDJET++ uses PYQUEN [30] which includes generation of initial parton spectra according to PYTHIA and production vertices is measured at a given impact parameter.…”

“…Further most of the existing models either consist of high p T particle production from jet fragmentation or involve low p T hadron production using thermal statistical processes. However, HYDJET++ model [28] consistently includes production of hard as well as soft p T hadrons, to calculate the charged hadron production in U + U collisions at center-of-mass energy √ s N N = 193 GeV. We study the pseudorapidity distribution, transverse momentum ( p T ) distribution of charged hadrons.…”

Is hexagonal flow ν6just a superposition of elliptic ν2and triangular ν3flows?

“…The description of the event generator HYDJET++ (HYDrodynamics with JETs) can be found elsewhere [12][13][14]. Recall briefly, that parametrized hydrodynamics is employed [13] to generate soft part of particle spectra, including hadron yields, femtoscopy correlations and differential elliptic flow.…”