Fast hadron freeze-out generator. II. Noncentral collisions

The fast Monte Carlo procedure of hadron generation developed in our previous work is extended to describe noncentral collisions of nuclei. We consider different possibilities to introduce appropriate asymmetry of the freeze-out hypersurface and flow velocity profile. For comparison with other models and experimental data, we demonstrate the results based on the standard parametrizations of the hadron freeze-out hypersurface and flow velocity profile assuming either a common chemical and thermal freeze-out or the chemically frozen evolution from chemical to thermal freeze-out. The ++ generator code is written under the framework and is available for public use at http://uhkm.jinr.ru/.

Figure 1

Typical hydrodynamic evolution scenario.

Figure 2

$m_t$ spectra (in $c^4$/GeV${}^2$) measured by the STAR Collaboration [29] for ${\pi }^{+}$ (circles), $K^{+}$ (squares), and $p$ (up-triangles)at $0\text{−}5\%$ centrality in comparison with model calculations at $T^{\mathrm{th}}=0.165$ (a), 0.130 (b), 0.100 (c) GeV, with the parameters from Table , for protons with weak decays taken into account (solid lines); for protons with weak decays not taken into account (dashed lines). The direct ${\pi }^{+},K^{+},$ and $p$ contributions are shown on (c) by dotted lines.

Figure 3

$m_t$ spectra (in $c^4$/GeV${}^2$) measured by the STAR Collaboration [29] for ${\pi }^{+}$ (circles), $K^{+}$ (squares), and $p$ (up-triangles) at different centralities compared with our FASTMC calculations at $T^{\mathrm{th}}=0.100$ GeV (solid lines) with the parameters from Tables and .

Figure 4

$p_t$ dependence of $v_2$ measured by the STAR Collaboration [32] (points) for charged particles at different centralities in comparison with our FASTMC calculations (solid lines) at $T^{\mathrm{th}}=0.100$ GeV with the parameters from Tables and .

Figure 5

$p_t$ dependence of $v_2$ measured by the STAR Collaboration [32] (points) for charged particles at centrality 20–30% compared with our FASTMC calculations under assumption of the single freeze-out at $T^{\mathrm{th}}=T^{\mathrm{ch}}=0.165$ GeV. The different sets of coordinate and momentum asymmetry parameters were tried: $\epsilon =0.1,\delta =0.3$ (lower solid line), $\epsilon =0.2,\delta =0.4$ (lower dotted line), $\epsilon =0.1,\delta =0.4$ (upper solid line), $\epsilon =0.2,\delta =0.5$ (upper dotted line), $\epsilon =0.15,\delta =0.4$ (dashed line).

Figure 6

${\pi }^{+}$ correlation radii at midrapidity in central Au+Au collisions at $\sqrt{s}{}_{\mathit{NN}}=200$ GeV from the STAR experiment [5] (open circles) and MC calculations within the Bjorken-like model with the parameters presented in Table in different intervals of the pair transverse momentum $k_t$. The full calculation with resonances (a), (b). (a) Single freeze-out $T^{\mathrm{ch}}=T^{\mathrm{th}}=0.165$ GeV, no weak decays (dashed line), with weak decays (solid line); (b) thermal freeze-out at $T^{\mathrm{th}}=0.130$ GeV occurs after the chemical one, weak decays are taken into account (solid line); (c) the full calculation with resonances, weak decays are taken into account at $T^{\mathrm{th}}=0.100$ GeV (solid line), the direct pions only (dotted lines).

Figure 7

Simulated with FASTMC squared correlation radii vs the azimuthal angle Φ of the ${\pi }^{+}{\pi }^{+}$ pair with respect to the reaction plane, $20\text{−}30\%$ centrality events in $k_T$ (GeV/$c$) intervals: $0.15<k_T<0.25$ (solid line), $0.25<k_T<0.35$ (dashed line), $0.35<k_T<0.45$ (dotted line), $0.45<k_T<0.60$ (dotted-dashed line). Simulation was done with the special set of parameters: $T^{\mathrm{th}}=0.1$ GeV, ${\rho }_u^{\max }(b=0)=1.0$; $R(b=0)=11.5$ fm, $\tau =7.5$ fm/$c,\Delta \tau =0$ fm/$c,\epsilon =0.1$ and $\delta =0.25$; weak decays were not taken into account.