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 s NN = 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 s NN . 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 K0S (a spin 0 hadron) in 20-40% central Pb–Pb collisions at s NN = 2.76 TeV are consistent with no spin alignment.