A suppression of the baryonic $Λ(1520)$ resonance yield relative to the $Λ$ ground state by $0.589 \pm 0.015^{\rm stat} \pm 0.086^{\rm syst}$ is observed in central relative to peripheral Pb-Pb collisions, with a significance of $6.8σ$. The $Λ(1520)$ production at midrapidity is measured in six centrality classes in Pb-Pb collisions for the first time at $\sqrt{s_{\rm NN}} = 5.02$ TeV with ALICE. The $Λ(1520)$ is a sensitive probe of late-stage hadronic interactions since its lifetime is comparable to that of the hadronic phase in heavy-ion collisions at the LHC. Statistical hadronization model calculations, predicting yields at chemical freeze-out, overestimate the measured ratio. The transverse-momentum spectra and the centrality dependence of the suppression are reproduced by the MUSIC hydrodynamic model only when coupled to the SMASH hadronic transport afterburner, which implements rescattering and regeneration in the late hadronic stage. The measurement, which represents the first observation of resonance suppression within a single collision system, provides a stringent test of the late-stage dynamics and evidence that hadronic interactions substantially modify reconstructible resonance yield.
Submitted to: PRL
e-Print: arXiv:2611.17010 | PDF | inSPIRE
CERN-EP-2026-302
Figure group
Figure 1
The \pt-differential \Lambdastar yields at midrapidity, \yless{0.5}, for six centrality classes. Solid, dashed, and dotted curves show predictions from the Blast-Wave model (normalized to data), MUSIC with and without the SMASH afterburner , respectively. Statistical and systematic uncertainties are indicated by bars and boxes, respectively. Shaded boxes indicate uncorrelated systematic uncertainties. |  |
Figure 2
The \average{\pt} of \Lambdastar as a function of \dnchdetacubic (red solid markers), compared with earlier data . Predictions from MUSIC with the SMASH afterburner , and MUSIC without the afterburner are shown as red dashed and magenta dotted lines, respectively, for \PbPb collisions at \sqrtsNN = 5.02 TeV. The Blast-Wave predictions are shown as green solid lines. Statistical and systematic uncertainties are indicated by bars and boxes, respectively. Shaded boxes indicate uncorrelated systematic uncertainties. |  |
Figure 3
The \pt-integrated \Lambdastar/\pLambda ratio as a function of \dnchdetacubic (red solid markers). Predictions from MUSIC with and without the SMASH afterburner are shown as red dashed and magenta dotted lines, respectively. CSM and PCE thermal model predictions are shown as green and yellow lines. The predictions from several SHMs are also included. Statistical and systematic uncertainties are indicated by bars and boxes, respectively. Shaded boxes indicate uncorrelated systematic uncertainties. |  |