The production of strange neutral baryons (Λ) and mesons (KS0) and the corresponding baryon-to-meson ratios are studied in two parts of the events separately – inside jets and in the event portion perpendicular to a jet cone. The ALICE detector can reconstruct them reliably even at high momenta via invariant-mass analysis using the charged particle tracks seen in the detectors.

The particles associated with the jets show the typical ratio known from the high momentum tail of the inclusive baryon-to-meson (pT>5 GeV/c) – essentially no enhancement – and similar values were found in both pp and p-Pb collisions, consistent with simulations of hard pp collisions using PYTHIA 8 (see figure). By contrast, however, the particles found away from jets do indeed show a baryon-to-meson enhancement that qualitatively resembles the observations in Pb-Pb collisions. The new study clarifies that the high rise of the ratio is associated with the soft part of the events (regions where no jet with more than pT=10 GeV/c is produced) and brings the first quantitative guidance for modelling the baryon-to-meson enhancement with an additional important constrain – the absence of the jet.

Further reading

ALICE Collaboration 2021