Strangeness production in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV using various model approaches

TL;DR

The study investigates strangeness production in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV to test for QGP-like behavior in small systems. It compares predictions from EPOS4's 3+1D viscous hydrodynamics with a QGP equation of state against AMPT's transport framework (Def and SM) for strange hadrons $K^0_{S}$, $\Lambda$, $\Xi$, $\phi$, and $\Omega$, focusing on $p_T$ spectra, $dN/dy$, and yield ratios relative to pions. Findings show EPOS4 yields higher strange-hadron production and stronger radial flow than AMPT, with strangeness-to-pion ratios rising with multiplicity and AMPT-SM enhanced by quark coalescence; a final-state multiplicity overlap with $p+p$, $p+Pb$, and $Pb+Pb$ systems suggests a continuum of production mechanisms. The results highlight limitations in current models to fully describe observed strangeness trends and emphasize that forthcoming $O+O$ data will constrain QGP-like interpretations in small systems.

Abstract

We present the predictions of various observables for strange ($\mathrm{K}^{0}_{\mathrm S}$, $Λ$($\overlineΛ$)) and multi-strange hadrons ($Ξ^-$($\overlineΞ^+$), $φ$, and $Ω^-$($\overlineΩ^+$)) using the recently updated 3+1D hydrodynamics-based EPOS4 framework and AMPT model. In this study, we report the transverse momentum (${p_{\rm T}}$) spectra, particle yields (${\mathrm{d}N/\mathrm{d}y}$), and ${p_{\rm T}}$ integrated yield ratios relative to pions for $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$~TeV. The results reveal that there are indications of stronger radial flow in EPOS4 compared to AMPT. We observe a final state multiplicity overlap with small ($p+p$ and $p+Pb$) and large ($Pb+Pb$) collision systems.

Figures (4)

• Figure 1: (Color online) Pseudo-rapidity distributions of charged particles in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV for different centrality classes using EPOS4 Identified_OOstrange_OO7 and AMPT-SM model. Marker style with different colors represent different centrality classes.
• Figure 2: (Color online) $p_T$-spectra of (multi-)strange hadrons ($\mathrm{K}^{0}_{\mathrm S}$, $\Lambda+\overline{\Lambda}$, $\Xi^{-}+\overline{\Xi}^{+}$, $\Omega^- + \overline{\Omega}^+$, and $\phi$) from EPOS4 and AMPT in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV for 0--5% centrality classes. $p_T$ spectra for different hadrons are scaled by a factor of $10$ for better visualization. In figure, solid lines represent EPOS4, while dashed lines correspond to AMPT-SM, and dotted lines represent AMPT-Def.
• Figure 3: (Color online) Multiplicity dependence of the integrated yield ($dN/dy$) at mid-rapidity $\mid y \mid< 0.5$ for (multi-)strange hadrons ($\mathrm{K}^{0}_{\mathrm S}$, $\Lambda$, $\Xi$, $\phi$, and $\Omega$) in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV using AMPT-Def, AMPT-SM and EPOS4.
• Figure 4: (Color online) $p_T$-integrated yield ratios of $K_S^0$, $\Lambda$, $\Xi$, $\phi$, and $\Omega$ to pions ($\pi^+ + \pi^-$) as a function of $\langle dN_{\text{ch}}/d\eta \rangle$ in $O+O$ collisions at $\sqrt{s_{\mathrm{NN}}}=7$ TeV using AMPT-Def, AMPT-SM and EPOS4. Solid lines are used for EPOS4, whereas the dotted and dashed lines represent the AMPT-Def and AMPT-SM models, respectively. The values are compared to the published results from $p+p$, $p+Pb$, and $Pb+Pb$ collisions alice_1alice_2alice_3alice_4.