Spin alignment measurements using vector mesons with ALICE detector at the LHC

Abstract

We present new measurements related to spin alignment of K∗0 vector mesons at mid-rapidity for Pb–Pb collisions at √sNN = 2.76 and 5.02 TeV. The spin alignment measurements are carried out with respect to production plane and 2nd order event plane. At low pT the spin density matrix element ρ00 for K∗0 is found to have values slightly below 1/3, while it is consistent with 1/3, i.e. no spin alignment, at high pT . Similar values of ρ00 are observed with respect to both production plane and event plane. Within statistical and systematic uncertainties, ρ00 values are also found to be independent of √sNN . ρ00 also shows centrality dependence with maximum deviation from 1/3 for mid-central collisions with respect to both the kinematic planes. The measurements for K∗0 in pp collisions at √s = 13 TeV and for K0 S (a spin 0 hadron) in 20-40% central Pb–Pb collisions at √sNN = 2.76 TeV are consistent with no spin alignment.