# SPIN 2018

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

## On the spin correlations of muons and tau leptons produced in the high-energy annihilation processes $e^+ e^- \rightarrow \mu^+ \mu^-, \tau^+ \tau^-$

11 Sep 2018, 17:55
25m

### A8

Parallel Sessions Spin Physics in Nuclear Reactions and Nuclei

### Speaker

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

### Description

The electromagnetic processes of annihilation of $(e^+ e^-)$ pairs -- which may be generated, in particular, in relativistic nucleus-nucleus and hadron-nucleus collisions -- into heavy flavor lepton pairs are theoretically studied in the one-photon approximation, using the technique of helicity amplitudes . For the process $e^+ e^- \rightarrow \mu^+\mu^-$, it is shown that -- in the case of the unpolarized electron and positron -- the final muons are also unpolarized but their spins prove to be strongly correlated. For the final $(\mu^+ \mu^-)$ system, the structure of triplet states is analyzed and explicit expressions for the components of the spin density matrix and correlation tensor are derived; besides, the formula for the angular correlation at the decays of the final $\mu^+$ and $\mu^-$ is obtained . It is demonstrated that the spin correlations of muons in the process $e^+ e^- \rightarrow \mu^+ \mu^-$, have the purely quantum character, since one of the Bell-type incoherence inequalities for the diagonal components of correlation tensor is always violated ( i.e., there is always one case when the modulus of sum of two diagonal components exceeds unity ) . In doing so, it is also established that, when involving the additional contribution of the weak interaction of lepton neutral currents through the virtual $Z^0$ boson, the qualitative character of the muon spin correlations does not change. Analogous consideration can be wholly applied as well to the annihilation process $e^+ e^- \rightarrow \tau^+ \tau^-$, which becomes possible at much higher energies.

### Primary author

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