# SPIN 2018

9-14 September 2018
University of Ferrara
Europe/Rome timezone
23RD INTERNATIONAL SPIN SYMPOSIUM

## Possible effect of mixed phase and deconfinement upon spin correlations in the $\Lambda \bar{\Lambda}$ pairs generated in relativistic heavy-ion collisions

11 Sep 2018, 17:30
25m

### A8

Parallel Sessions Spin Physics in Nuclear Reactions and Nuclei

### Speaker

Dr Valery Lyuboshitz (Joint Institute for Nuclear Research ( Dubna ))

### Description

Spin correlations for the $\Lambda \Lambda$ and $\Lambda \bar{\Lambda}$ pairs, generated in relativistic heavy-ion collisions, and related angular correlations at the joint registration of space-parity nonconserving hadronic decays of two hyperons are theoretically analyzed. These correlations give important information about the character and mechanism of multiple processes, and the advantage of the $\Lambda \Lambda$ and $\Lambda \bar{\Lambda}$ systems over other ones is due to the fact that the $P$-odd decays $\Lambda \rightarrow p + \pi^-$ and $\bar{\Lambda} \rightarrow \bar{p} + \pi^+$ serve as effective analyzers of spin state of the $\Lambda$ and $\bar{\Lambda}$ particles -- thus, the respective spin correlations can be rather easily distinguished and studied experimentally, which is especially meaningful for the investigations of multiple generation at modern and future ion colliders like RHIC, LHC and NICA . The correlation tensor components can be derived by the method of "moments" -- as a result of averaging the combinations of trigonometric functions of proton ( antiproton ) flight angles over the double angular distribution of flight directions for products of two decays. The properties of the "trace" of the correlation tensor ( a sum of three diagonal components ), determining the angular correlations as well as the relative fractions of the triplet states and singlet state of respective pairs, are discussed. In this talk, spin correlations for two identical particles ($\Lambda \Lambda$) and two non-identical particles ($\Lambda \bar{\Lambda}$) are generally considered from the viewpoint of the conventional model of one-particle sources, which implies that correlations vanish at enough large relative momenta. However, under these conditions ( especially at ultrarelativistic energies ), in the case of two non-identical particles ($\Lambda \bar{\Lambda}$) the two-particle annihilation sources -- quark-antiquark and two-gluon ones -- start playing a noticeable role and lead to the difference of the correlation tensor from zero. In particular, such a situation may arise, when the system passes through the "mixed phase" and -- due to the multiple production of free quarks and gluons in the process of deconfinement of hadronic matter -- the number of two-particle sources strongly increases.

### Primary author

Dr Valery Lyuboshitz (Joint Institute for Nuclear Research ( Dubna ))