# EPS-HEP2021 conference

26-30 July 2021
Zoom
Europe/Berlin timezone

## Limits for anomalous magnetic and electric dipole moments of tau leptons from heavy-ion UPCs

Not scheduled
20m
Zoom

#### Zoom

Poster Heavy Ion Physics

### Speakers

Mariola Kłusek-Gawenda (IInstitute of Nuclear Physics Polish Academy of Sciences) Antoni Szczurek (Institute of Nuclear Physics PAN, Krakow and Rzeszow University, Rzeszow)

### Description

Physics of ultraperipheral ultrarelativistic heavy-ion collisions gives an excellent opportunity to study photon-photon interaction. Vast moving charged particles are surrounded by an electromagnetic field that can be considered as a source of (almost real) photons. The photon flux scales as the square of the nuclear charge, so $^{208}$Pb has a considerable advantage over protons as far as the flux of photons is considered. We would like to report our analysis on the possibility to set limits on anomalous magnetic and/or electric dipole moments of $\tau$ leptons produced in ultraperipheral heavy ion collisions.

We shall discuss the dependence of $\gamma\gamma \to \tau^+\tau^-$ differential cross section on anomalous magnetic and electric dipole couplings of photons to $\tau$ lepton. A similar analysis is done for ultraperipheral Pb+Pb collisions at the LHC. We investigate the sensitivity on $a_\tau$ and $d_\tau$, assuming standard LHC detectors using the currently available as well as future datasets. In particular, we propose to use cross section ratios of the $\gamma \gamma \to \tau^+ \tau^-$ and $\gamma \gamma \to e^+ e^- / \mu^+ \mu^-$ processes to probe anomalous magnetic and electric dipole moments. This trick allows to cancel several systematic uncertainties. Due to a short lifetime of $\tau$ lepton, the experimental knowledge on $a_{\tau}$ is worse by several orders of magnitude than those for of $a_e$ and $a_\mu$. Our studies show that the currently available sample of the LHC experiments is already sufficient to improve the sensitivity on $a_\tau$ by a factor of two compared to the best LEP2 result. Hence, we consider this analysis as highly interesting and worthwhile to be done in the future.

Published in: Phys. Lett. B809 (2020) 135682,
M. Dyndal, M. Klusek-Gawenda, M. Schott and A. Szczurek,
"Anomalous electromagnetic moments of $\tau$ lepton in $\gamma \gamma \to \tau^+ \tau^-$ reaction in Pb+Pb collisions at the LHC"

Collaboration / Activity Theory mariola.klusek@ifj.edu.pl Mariola Klusek-Gawenda

### Primary authors

Mariola Kłusek-Gawenda (IInstitute of Nuclear Physics Polish Academy of Sciences) Antoni Szczurek (Institute of Nuclear Physics PAN, Krakow and Rzeszow University, Rzeszow)