Aperitivo Scientifico: Probing the evolution of heavy-ion collisions with hadronic resonances measured by ALICE at the LHC

by Dr. Neelima Agrawal (Indian Institue of Technology Bombay)

Friday, 6 October 2017 from to (Europe/Rome)
at Bologna ( sala Riunioni 1 piano Berti Pichat )
The observation of the modification of hadronic resonance production in heavy-ion collisions provides insight into the existence and the characteristics of a prolonged hadronic phase after hadronisation. If such hadronic phase lasts long enough, the decay daughters of very short-lived resonances experience its full evolution and suffer re-scattering in the dense hadronic medium, which could modify their correlations and hence the experimentally measured resonance yields.
The ALICE experiment has measured the production of a rich set of hadronic resonances, such as ρ(770)0, K*(892)0, Φ(1020), Σ(1385)±, Λ(1520) and Ξ(1530)0, in pp, p-Pb and Pb-Pb collisions at various energies at the LHC. A comprehensive overview of the results will be presented. The results are compared to Monte Carlo event generators, including EPOS3 with UrQMD afterburner, and predictions from statistical hadronisation models.
Special focus will be given to new results on the first measurement of Λ(1520) resonance production in Pb-Pb collisions at √sNN = 2.76 TeV and the corresponding analysis. The EPOS3 model reproduces the measured pT spectral shapes, ⟨pT⟩ and the trend of the suppression reasonably well when coupled with UrQMD, whereas the agreement with the data significantly degrades when the UrQMD is absent. This is an important observation in heavy-ion collisions due to the Λ(1520) characteristic life time of 12.6 fm/c, which lies in between the lifetimes of the suppressed K*(892)0 and the unmodified Φ(1020) meson of 4.16 and 46.3 fm/c, respectively. The observation of the suppression of the production of Λ(1520) resonances in central Pb-Pb collisions with respect to peripheral collisions at √sNN = 2.76 TeV adds further support to the existence of such a dense hadronic phase, as already evidenced by K*/K and ρ/π measurements.