Identified-particle production in Xe $+$ Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV using a multiphase transport model

Xe+Xe collisions at relativistic energies provide us with an opportunity to study a possible system with deconfined quarks and gluons, whose size is in between those produced by $p+p$ and Pb+Pb collisions. In the present work, we have used a multiphase transport (AMPT) model with nuclear deformation to study the identified particle production, such as (${\pi }^{+}+{\pi }^{-}$), ($K^{+}+K^{-}$), $K_s^0$, ($p+\overline{p}$), $\varphi$, and ($\mathrm{\Lambda }+\overline{\mathrm{\Lambda }}$) in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. We study the $p{}_{\mathrm{T}}$ spectra, integrated yield, and $p{}_{\mathrm{T}}$-differential and $p{}_{\mathrm{T}}$-integrated particle ratios to (${\pi }^{+}+{\pi }^{-}$) and ($K^{+}+K^{-}$) as a function of collision centrality. The particle ratios are focused on strange to nonstrange ratios and baryon to meson ratios. The effect of deformations has also been highlighted by comparing our results to the nondeformation case. We have also compared the results from AMPT string melting and the AMPT default version to explore possible effects of the coalescence mechanism. We observe that the differential particle ratios show strong dependence on centrality while the integrated particle ratios show no centrality dependence. We give a thermal model estimation of chemical freeze-out temperature and the Boltzmann-Gibbs Blast Wave analysis of kinetic freeze-out temperature and collective radial flow in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$.

Figure 1

The nuclear density profile for the xenon nucleus. Shown are the hard sphere, Woods-Saxon, and deformed Woods-Saxon density profiles. The bottom panel shows the ratio of nuclear deformation to nondeformation for the xenon nucleus.

Figure 2

$p{}_{\mathrm{T}}$ spectra of identified particles in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$ for 0–10% centrality using AMPT-SM. Different symbols show different particle species. The vertical lines in the results show the statistical uncertainties.

Figure 3

$p{}_{\mathrm{T}}$-differential particle ratios of kaons (a), protons (b), $\varphi$ (c), and $\mathrm{\Lambda }$ (d) to pions in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. Different symbols show various centrality bins. The vertical lines in the data points are the statistical uncertainties.

Figure 4

$p{}_{\mathrm{T}}$-differential $p$-to-$K$ (a) and $\mathrm{\Lambda }$-to-$K$ (b) ratios for various centrality bins in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. The vertical lines in the data points are the statistical uncertainties.

Figure 5

$p{}_{\mathrm{T}}$-integrated ratios of identified particles to pions (a) and kaons (b) as a function of centrality. Different symbols are for different particles. The statistical uncertainties are within symbol sizes.

Figure 6

$p{}_{\mathrm{T}}$-integrated kaon-to-pion ratio as a function of charged-particle multiplicity for $p+p$ collisions at $\sqrt{s}=7\mathrm{TeV}$, Pb+Pb collisions at $\sqrt{s_{NN}}=2.76\mathrm{TeV}$, and Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. The ratios for $p+p$, Xe+Xe, and Pb+Pb collisions are from ALICE experimental data [46, 54, 57]. The ratio for Xe+Xe collisions from AMPT-SM seems to agree with the experimental data within uncertainties. The experimental data from $p+p$ collisions are for $K_s^0/\pi$, while for others the ratio is $(K^{+}+K^{-})/({\pi }^{+}+{\pi }^{-})$.

Figure 7

$p{}_{\mathrm{T}}$-differential $p$-to-$\pi$ (a), $\mathrm{\Lambda }$-to-$K_s^0$ (b), and $p$-to-$\varphi$ (c) ratios for most central (0–10%) Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$. Red and black markers are predictions from AMPT-Default and AMPT-SM, respectively. The ALICE preliminary data [54] are shown in blue markers. The error bars in the results from models are the statistical uncertainties.

Figure 8

The kinetic freeze-out temperature $T_{\mathrm{kin}}$ and the chemical freeze-out temperature $T_{\mathrm{ch}}$ as a function of collision centrality in Xe+Xe collisions at $\sqrt{s_{NN}}=5.44\mathrm{TeV}$.