Enhanced production of multi-strange hadrons in high-multiplicity proton–proton collisions

J Adam, Didier Alexandre, Harry Andrews, Lee Barnby, David Evans, Katie Graham, Peter Jones, Anton Jusko, Marian Krivda, Roman Lietava, Orlando Villalobos Baillie, Nima Zardoshti, ALICE Collaboration

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233 Citations (Scopus)
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At sufficiently high temperature and energy density, nuclear matter undergoes a transition to a phase in which quarks and gluons are not confined: the quark–gluon plasma (QGP)1. Such an exotic state of strongly interacting quantum chromodynamics matter is produced in the laboratory in heavy nuclei high-energy collisions, where an enhanced production of strange hadrons is observed2, 3, 4, 5, 6. Strangeness enhancement, originally proposed as a signature of QGP formation in nuclear collisions7, is more pronounced for multi-strange baryons. Several effects typical of heavy-ion phenomenology have been observed in high-multiplicity proton–proton (pp) collisions8, 9, but the enhanced production of multi-strange particles has not been reported so far. Here we present the first observation of strangeness enhancement in high-multiplicity proton–proton collisions. We find that the integrated yields of strange and multi-strange particles, relative to pions, increases significantly with the event charged-particle multiplicity. The measurements are in remarkable agreement with the p–Pb collision results10, 11, indicating that the phenomenon is related to the final system created in the collision. In high-multiplicity events strangeness production reaches values similar to those observed in Pb–Pb collisions, where a QGP is formed.
Original languageEnglish
Pages (from-to)535-539
Number of pages5
JournalNature Physics
Publication statusPublished - 24 Apr 2017


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