Mechanism behind strangeness enhancement in small collision systems

Determine the exact microscopic production mechanism responsible for the observed increase in strangeness in small collision systems, specifically high-multiplicity proton–proton and proton–lead collisions at LHC energies, as quantified by strange-to-non-strange hadron yield ratios.

Background

Strangeness enhancement—an increased production of strange and multi-strange hadrons—has long been a signature associated with quark–gluon plasma formation in heavy-ion collisions. Surprisingly, recent measurements at the LHC show that strangeness enhancement also appears in high-multiplicity proton–proton and proton–lead collisions, scaling smoothly with event multiplicity across systems.

While several theoretical approaches (statistical thermal models, color reconnection and rope hadronization, and core–corona models) qualitatively reproduce aspects of the enhancement in small systems, the underlying microscopic mechanism driving the increase remains unresolved. This paper uses h–φ(1020) two-particle angular correlations in p–Pb collisions at √sNN = 5.02 TeV to separate jet-like from underlying-event-like production, aiming to clarify the origin of strangeness enhancement by comparing φ-to-hadron ratios in distinct angular regions.