Suppression of Λ(1520) resonance production in central Pb-Pb collisions at s NN =2.76 TeV

Abstract

The production yield of the $\mathrm{\ensuremath{\Lambda}}(1520)$ baryon resonance is measured at midrapidity in Pb-Pb collisions at $\sqrt{{s}_{\mathit{NN}}}$ = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is performed in the $\mathrm{\ensuremath{\Lambda}}(1520)\ensuremath{\rightarrow}\mathrm{p}{\mathrm{K}}^{\ensuremath{-}}$ (and charge conjugate) hadronic decay channel as a function of the transverse momentum (${p}_{\mathrm{T}}$) and collision centrality. The ratio of the ${p}_{\mathrm{T}}$-integrated production of $\mathrm{\ensuremath{\Lambda}}(1520)$ baryons relative to $\mathrm{\ensuremath{\Lambda}}$ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first $3\ensuremath{\sigma}$ evidence of $\mathrm{\ensuremath{\Lambda}}(1520)$ suppression within a single collision system. The measured $\mathrm{\ensuremath{\Lambda}}(1520)/\mathrm{\ensuremath{\Lambda}}$ ratio in central collisions is smaller than the value predicted by the statistical hadronization model calculations. The shape of the measured ${p}_{\mathrm{T}}$ distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances.