scholarly journals Study of Lambda polarization at RHIC BES and LHC energies

2018 ◽  
Vol 171 ◽  
pp. 17001 ◽  
Author(s):  
Iurii Karpenko ◽  
Francesco Becattini

In hydrodynamic approach to relativistic heavy ion collisions, hadrons with nonzero spin, produced out of the hydrodynamic medium, can acquire polarization via spin-vorticity thermodynamic coupling mechanism. The hydrodynamical quantity steering the polarization is the thermal vorticity, that is minus the antisymmetric part of the gradient of four-temperature field. Based on this mechanism there have been several calculations in hydrodynamic and non-hydrodynamic models for non-central heavy ion collisions in the RHIC Beam Energy Scan energy range, showing that the amount of polarization of produced Λ hyperons ranges from few percents to few permille, and decreases with collision energy. We report on an extension of our existing calculation of global Λ polarization in UrQMD+vHLLE model to full RHIC and LHC energies, and discuss the component of polarization along the beam direction, which is the dominant one at high energies.

2017 ◽  
Vol 96 (4) ◽  
Author(s):  
L. Adamczyk ◽  
J. K. Adkins ◽  
G. Agakishiev ◽  
M. M. Aggarwal ◽  
Z. Ahammed ◽  
...  

Author(s):  
Mario Motta ◽  
Rainer Stiele ◽  
Wanda Maria Alberico ◽  
Andrea Beraudo

Abstract We study the isentropic evolution of the matter produced in relativistic heavy-ion collisions for various values of the entropy-per-baryon ratio of interest for the ongoing and future experimental searches for the critical endpoint (CEP) in the QCD phase diagram: these includes the current beam-energy-scan (BES) program at RHIC and the fixed-target collisions foreseen for the near future at various facilities. We describe the hot-dense matter through two different effective Lagrangians: the PNJL (Polyakov–Nambu–Jona–Lasinio) and the PQM (Polyakov-quark-meson) models. We focus on quantities expected to have a direct experimental relevance: the speed of sound, responsible for the collective acceleration of the fireball, and the generalized susceptibilities, connected to the cumulants of the distributions of conserved charges. In principle they should affect the momentum spectra and the event-by-event fluctuations of the yields of identified particles. Taking realistic values for the initial temperature and the entropy-per-baryon ratio we study the temporal evolution of the above quantities looking for differences along isentropic trajectories covering different regions of the QCD phase diagram, passing far or close to the CEP or even intersecting the first-order critical line.


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