PUBLICATION: CHINESE PHYSICS C

AUTHORS: Shen, DY; Chen, JH; Lin, ZW

Spin alignments of vector mesons and hyperons in relativistic heavy-ion collisions have been proposed as signals of global polarization. The STAR experiment first observed the polarization. Recently, the ALICE collaboration measured the transverse momentum (p(T)) and the collision centrality dependence of K*, and phi spin alignments during Pb-Pb collisions at root s(NN) = 2.76 TeV. A large signal is observed in the low p(T) region of mid-central collisions for K*, while the signal is much smaller for phi, and these have not been understood yet. Since vector mesons have different lifetimes and their decay products have different scattering cross sections, they suffer from different hadronic effects. In this paper, we study the effect of hadronic interactions on the spin alignment of K*, phi, and rho mesons in relativistic heavy-ion collisions with a multi-phase transport model. We find that hadronic scatterings lead to a deviation of the observed spin alignment matrix element rho(00) away from the true value for rho and K* mesons (with a bigger effect on rho) while the effect is negligible for the phi meson. The effect depends on the kinematic acceptance: the observed rho(00) value is lower than the true value when the pseudorapidity (eta) coverage is small, while there is little effect when the eta coverage is large. Hence, this study provides valuable information to understand the vector meson spin alignment signals observed during the experiments.

 

LINKS: http://dx.doi.org/10.1088/1674-1137/abe763