Longitudinal $\bar{\Lambda}_0$ polarization in heavy-ion collisions as a probe for QGP formation

Abstract

We present an analysis of the longitudinalΛ 0 polarization in ultrarelativistic heavy-ion collisions. The polarization ofΛ 0 's coming from the decay chainΞ →Λ 0 + π exhibits a very well differentiated behavior depending on the production region of the primordialΞ's. This effect reflects the different values of the NΞ/NΛ 0 ratio in the QGP region, where nucleon-nucleon interactions take place in a hot and dense environment, and the peripherical region, in which ordinary nucleon-nucleon interactions occur. An increase in the longitudinal Λ 0 polarization signals a strangeness enhancement which is thought as a property of the QGP phase.

Polarization of Λ0 hyperons in nucleus-nucleus collisions at high energies

“…One of the new signature can be the change of in the polarization properties of the secondary particles in the nucleus-nucleus collisions compared to the nucleon-nucleon collisions. A number of polarization observables have been proposed as a possible signature of phase transition, namely, decreasing of the Λ 0 transverse polarization in central collisions [1,2], non-zero Λ0 longitudinal polarization [3,4], non-zero J/Ψ polarization at low p T [5], anisotropy in di-electron production from vector mesons decay [6] (and references therein), global hyperon polarization [7] and spin-alignment of vector mesons [8] in non-central events etc.…”