Multiplicity dependence of K*(892) ±  production in pp collisions at √𝑠 = 13 TeV

Abstract

The first results of K*(892)±  production at midrapidity (|y| < 0.5) in pp collisions at √𝑠 = 13 TeV as a function of the event multiplicity are presented. The K*(892) ±  has been reconstructed via its hadronic decay channel K*(892)± → π± + K0S using the ALICE detector at the LHC. For each multiplicity class, the differential transverse momentum (pT) spectrum, the mean transverse momentum ⟨pT⟩, the pT-integrated yield (dN/dy), and the ratio of the K*(892) ±  to K0S yields are reported. These are consistent with previous K*(892)0 resonance results with a higher level of precision. Comparisons with phenomenological models such as PYTHIA6, PYTHIA8, EPOS-LHC, and DIPSY are also discussed. For the first time, a significant K*(892) ± /K0S suppression in pp collisions is observed at a 7σ level passing from low to high multiplicity events. The ratios of the pT-differential yields of K*(892) ±  and K0S in high and low multiplicity events are also presented along with their double ratio. For pT ≲ 2 GeV/c this double ratio persists below unity by more than 3σ suggesting that the suppression affects mainly low pT resonances. The measured decreasing trend of the K*(892) ± /K0S ratio with increasing multiplicity, which in heavy-ion collisions is typically attributed to the rescattering of decay particles of the short-lived resonances, is reproduced by the EPOS-LHC model without the use of hadronic afterburners.