The collective expansion and hydrodynamic evolution in heavy-ion collisions is well established. However, whether femtometer-scale droplets of quark-gluon plasma (QGP) are produced in small systems at high energies remains a fundamental open question. Analysis of Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, Xe-Xe collisions at $\sqrt{s_{NN}}$ = 5.44 TeV, and O-O collisions at $\sqrt{s_{NN}}$ = 5.36 TeV using EPOS4 is reported to make predictions and postdictions. The results are compared with ALICE data for Pb-Pb and Xe-Xe collisions. Charged particle multiplicity $(\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta )$ and transverse-momentum $\left(p_{\mathrm{T}}\right)$ spectra for pions $\left({\pi }^{\pm }\right)$, kaons $\left(K^{\pm }\right)$, and protons $\left[p\left(\overline{p}\right)\right]$ are studied. The inclusion of a hadronic afterburner, UrQMD (Ultrarelativistic Quantum Molecular Dynamics) is found to be necessary to correctly describe baryon yields. $p_{\mathrm{T}}$ fluctuations are also studied via normalized $p_{\mathrm{T}}$ correlator, $\sqrt{\langle \langle \mathrm{\Delta }{p}_{\mathrm{T},i}\mathrm{\Delta }{p}_{\mathrm{T},j}\rangle \rangle }/\langle \langle p_{\mathrm{T}}\rangle \rangle$. Lastly, anisotropic flow harmonics $(v_2\left\{2\right\},$ $v_3\left\{2\right\})$ are computed as a function of $p_{\mathrm{T}}$ and centrality. Since EPOS4 has not been extensively studied for flow observables, this study thereby provides a nontrivial assessment of its collective dynamics. The results are compared with experiment wherever data are available. Taken together, this study provides a unified description of soft observables from Pb-Pb through Xe-Xe down to O-O and offers quantitative guidance on how such collisions may inform of the properties of the QGP.

Close

PrevNext

View figure in article

• Relativistic heavy-ion collisions