$\tau$-lepton pair spin in proton-proton LHC collisions for anomalous dipole moments

TL;DR

This paper investigates how the spin correlations of tau lepton pairs produced in high-energy proton-proton collisions at the LHC can reveal potential anomalous dipole moments, using a semi-realistic observable based on decay products.

Contribution

It introduces a method to probe weak anomalous magnetic and electric dipole moments of tau leptons through spin correlation analysis in proton-proton collisions.

Findings

The spin-correlation matrix depends on anomalous moments.

A semi-realistic observable sensitive to these moments is constructed.

The observable can potentially detect weak anomalous dipole moments.

Abstract

The spin correlations in the pair of $\tau$ leptons produced in the high-energy proton-proton collisions are studied. The invariant mass of the $\tau$-lepton pair is chosen close to $Z$-boson mass, in these conditions $Z$-boson exchange gives the dominant contribution to the Drell-Yan mechanism. The interaction of $Z$ boson with $\tau$ lepton, in addition to the Standard Model couplings, can include weak anomalous magnetic and electric dipole moments (or form-factors) of the $\tau$ lepton. Dependence of elements of the $pp$ spin-correlation matrix on the weak anomalous moments is determined for various regions of the rapidity of the $\tau$-lepton pair. Based on this calculation, we construct a semi-realistic observable built on the momenta of pions in the $\tau^\mp \to \pi^\mp \nu_\tau$ and $\tau^\pm \to \rho^\pm \nu_\tau \to \pi^\pm \pi^0 \nu_\tau$ decay channels, and show that this observable can be sensitive to the weak anomalous dipole moments.