Production of Ξ and Ω hyperons in high-multiplicity proton–proton collisions at √s = 13 TeV

This paper presents the first measurements of Ξ Ξ and Ω Ω hyperon yields at the highest multiplicities reached in pp collisions at √s=13 s = 13 TeV. This measurement exploits the high-multiplicity pp collisions collected by ALICE with dedicated triggers. The selected collisions are characterised by about 30 charged particles per unit of rapidity, over four times more than in minimum-bias pp collisions at the same centre-of-mass energy, and about twice as many as in minimum-bias p–Pb or very peripheral Pb–Pb collisions at similar energies. The production yields and average transverse momenta of the hyperons agree with trends indicated by previous measurements in pp collisions at lower multiplicities. The difference in average transverse momenta between pp and p–Pb collisions, observed with the new high-multiplicity pp data, provides additional insight into the underlying particle production mechanisms in small collision systems. The results support a strong correlation between multi-strange hadron yields and final-state multiplicity regardless of the collision system at the LHC energies, extending this observation to the highest multiplicity reached in pp collisions. The comparison with several state-of-the-art models suggests that the description of strange-hadron production is improved by recently introduced features such as interactions between overlapping strings in Pythia 8.2 with Ropes and the collective expansion of high-density string regions in EPOS4.