ALICE measures strangeness enhancement at its extremes

About

Over the past 15 years, the ALICE Collaboration has investigated the so-called strangeness enhancement, typically quantified via the ratio of strange-hadron to pion yields. When measured as a function of charged-particle multiplicity at midrapidity, this ratio exhibits a smooth evolution across collision systems and energies, suggesting that strange-hadron production is primarily connected to the overall event activity and is largely insensitive to the initial conditions.

In recently published studies [1,2], ALICE has completed a comprehensive analysis of strange-to-non-strange hadron yield ratios in pp and Pb–Pb collisions at $\sqrt{s_{\rm {NN}}}$ = 5.02 TeV, extending previous measurements with unprecedented precision over a multiplicity range from ~2 to ~2000 charged particles at midrapidity.

Motivated by the observations in pp collisions, the collaboration has taken a further step towards understanding strangeness-production mechanisms by measuring, for the first time, the event-by-event probability of forming multiple strange particles of the same species [3].

In this seminar, the first ALICE measurement of the multiplicity distribution P($\textit{n}_{\rm S}$) for $\rm{K}^{0}_{\rm S}$, $\Lambda$, $\Xi$ and $\Omega$ in pp collisions at $\sqrt{s}$ = 5.02 TeV as a function of charged-particle multiplicity is shown, extending beyond average yields and probing higher orders of the strange-particle production probability distribution.

From the P($\textit{n}_{\rm S}$) distribution, average yields of $\textit{n}$-particle multiplets per event are calculated, taking into account all possible combinations that lead to a given multiplet. This allows the comparison between events with the same (or different) overall strange-quark content that hadronize into various hadronic final states. The results are compared with state-of-the-art phenomenological models implemented in widely used Monte Carlo event generators, providing enhanced sensitivity to the underlying…