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 ))
Co-author
Dr
Vladimir Lyuboshitz
(JINR, Dubna)
