Abstract
The production yield of the $\Lambda(1520)$ baryon resonance is measured at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with the ALICE detector at the LHC. The measurement is performed in the $\Lambda(1520)\rightarrow {\rm pK}^{-}$ (and charge conjugate) hadronic decay channel as a function of the transverse momentum ($p_{\rm T}$) and collision centrality. The $p_{\rm T}$-integrated production rate of $\Lambda(1520)$ relative to $\Lambda$ 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$\sigma$ evidence of $\Lambda(1520)$ suppression within a single collision system. The measured $\Lambda(1520)/\Lambda$ ratio in central collisions is smaller than the value predicted by the statistical hadronisation model calculations. The shape of the measured $p_{\rm T}$ 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.
Highlights
High-energy heavy-ion collisions provide an excellent means to study the properties of nuclear matter under extreme conditions and the phase transition to a deconfined state of quarks and gluons predicted by lattice QCD calculations [2]
The good agreement of the blast-wave predictions with the data is consistent with the scenario where (1520) undergoes a similar hydrodynamic evolution as pions, kaons, and protons with a common transverse expansion velocity that increases with centrality
The pT distributions are compared to predictions of the EPOS3 model [11], a Monte Carlo generator founded on parton-based Gribov-Regge theory, which describes the full evolution of a heavy-ion collision
Summary
High-energy heavy-ion collisions provide an excellent means to study the properties of nuclear matter under extreme conditions and the phase transition to a deconfined state of quarks and gluons (quark-gluon plasma, QGP [1]) predicted by lattice QCD calculations [2]. The bulk properties of the matter created in high-energy nuclear reactions have been widely studied at the Relativistic Heavy Ion Collider (RHIC) and at the Large Hadron Collider (LHC) and are well described by hydrodynamic and statistical models. The relative abundances of stable particles are consistent with chemical equilibrium and are successfully described by statistical hadronization models (SHMs) [4,5,6]. They are determined by the “chemical freeze-out” temperature Tch and the baryochemical potential μB [4,7], reflecting the thermodynamic characteristics of the chemical freeze-out.
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