On ambiguity of definition of shear and spin-hall contributions to Λ polarization in heavy-ion collisions
Yu. B. Ivanov+*×, A. A. Soldatov*
+Bogoliubov Laboratory for Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia
*National Research Nuclear University "MEPhI", 115409 Moscow, Russia
×National Research Centre "Kurchatov Institute", 123182 Moscow, Russia
Recently proposed thermal-shear and spin-Hall contributions to the
particle polarization in heavy-ion collisions
are discussed. Alternative definitions of the thermal-shear contribution,
i.e. those of
Becattini-Buzzegoli-Palermo on the one hand and Liu-Yin on the other,
are very similar in the midrapidity region while quite different at
which are measured in fixed-target experiments. It is shown that the
thermal-shear contribution to the global polarization
with momentum averaging extended to all momenta is very different within
these alternative definitions.
The spin-Hall contribution to the global polarization, defined similarly
the Liu-Yin shear one, is identically zero, if averaging runs
over all momenta. Only application of restrictive momentum acceptance
and the boost (to Λ rest frame) correction result in nonzero
global spin-Hall polarization.
If the spin-Hall contribution were defined similarly to Becattini-Buzzegoli-Palermo shear one,
the global spin-Hall polarization would be non-zero even without any
acceptance and the boost correction.