CMS-PAS-HIN-25-020

CMS-PAS-HIN-25-020
Observation of enhanced baryon production using strange hadrons in OO collisions at 5.36$ \mathrm{TeV} $
CMS Collaboration
2026-07-06

Abstract: A hot deconfined medium known as the quark-gluon plasma (QGP) is created in collisions of ultrarelativistic heavy nuclei. In these systems, hadron production is strongly modified relative to proton–proton (pp) interactions. In the transverse momentum region 2 $ < p_\mathrm{T} < $ 5 GeV, collective radial flow and quark coalescence are important mechanisms that can produce such modifications. While these effects are well-established for collisions of large ions, such as lead, it is unknown if they are present in systems produced using smaller ions. To address this question, the $ p_\mathrm{T} $ spectra of two strange hadrons, $ \mathrm{K}^{0}_{\mathrm{S}} $ and $ \Lambda $, are measured in oxygen–oxygen (OO) and pp collisions at a center-of-mass energy per nucleon pair of $ \sqrt{s_{\mathrm{NN}}} = $ 5.36 TeV. The measurements are produced using the CMS detector at the LHC, and the OO and pp datasets correspond to integrated luminosities of 6.8$ \mathrm{nb}^{-1} $ and 1.1$ \mathrm{pb}^{-1} $, respectively. The spectral modification of $ \mathrm{K}^{0}_{\mathrm{S}} $ mesons in OO collisions relative to pp collisions is found to be similar to that of inclusive charged hadrons. Conversely, the relative production of $ \Lambda $ baryons in OO versus pp collisions exhibits a pronounced enhancement when compared to $ \mathrm{K}^{0}_{\mathrm{S}} $. A baryon-to-meson enhancement is observed in OO collisions, suggesting the formation of a deconfined medium, and offering insight into the roles of strangeness, radial flow, and quark coalescence in QGP.
Links: CDS record (PDF) ; CADI line (restricted) ; These preliminary results are superseded in this paper, Submitted to PRL. The superseded preliminary plots can be found here.

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