Production of KS0, Λ ((Λ)over-bar), Ξ±, and Ω± in jets and in the underlying event in pp and p-Pb collisions

The production of strange hadrons (K-S(0), Lambda, Xi(+/-), and Omega(+/-)), baryon-to-meson ratios (Lambda/K-S(0), Xi/K-S(0), and Omega/K-S(0)), and baryon-to-baryon ratios (Xi/Lambda, Omega/Lambda, and Omega/Xi) associated with jets and the underlying event were measured as a function of transverse momentum (pT) in pp collisions at root s = 13TeV and p-Pb collisions at root s(NN) = 5.02TeV with the ALICE detector at the LHC. The inclusive production of the same particle species and the corresponding ratios are also reported. The production of multi-strange hadrons, Xi(+/-) and Omega(+/-), and their associated particle ratios in jets and in the underlying event are measured for the first time. In both pp and p-Pb collisions, the baryon-to-meson and baryon-to-baryon yield ratios measured in jets differ from the inclusive particle production for low and intermediate hadron p(T) (0.6-6 GeV/ c). Ratios measured in the underlying event are in turn similar to those measured for inclusive particle production. In pp collisions, the particle production in jets is compared with Pythia 8 predictions with three colour-reconnection implementation modes. None of them fully reproduces the data in the measured hadron pT region. The maximum deviation is observed for Xi(+/-) and Omega(+/-) which reaches a factor of about six. The event multiplicity dependence is further investigated in p-Pb collisions. In contrast to what is observed in the underlying event, there is no significant event-multiplicity dependence for particle production in jets. The presented measurements provide novel constraints on hadronisation and its Monte Carlo description. In particular, they demonstrate that the fragmentation of jets alone is insufficient to describe the strange and multi-strange particle production in hadronic collisions at LHC energies.

Automated summary

In this study, the production of strange hadrons, baryon-to-meson ratios, and baryon-to-baryon ratios in association with jets and the underlying event were measured in collisions at the LHC. The results show that the production of particles in jets deviates from the inclusive production, while the ratios in the underlying event are similar to those in the inclusive production. Additionally, the Pythia 8 predictions do not fully reproduce the measured data, indicating that jet fragmentation alone is insufficient to describe the production of strange and multi-strange particles at LHC energies. Furthermore, the event multiplicity dependence for particle production in jets is found to be insignificant.