A study of the measurement of the $\tau$ lepton anomalous magnetic moment in high energy lead-lead collisions at LHC

Abstract

The $\tau$ lepton anomalous magnetic moment: $a_{\tau }=\frac{g_{\tau }-2}{2}$ was measured, so far, with a precision of only several percents despite its highly sensitivity to physics beyond the Standard Model such as compositeness or Supersymmetry. A new study is presented to improve the sensitivity of the $a_{\tau }$ measurement with photon-photon interactions from ultra-peripheral lead-lead collisions at LHC. The theoretical approach used in this work is based on an effective Lagrangian and on a photon flux implemented in the MadGraph5 Monte Carlo simulation. Using a multivariate analysis to discriminate the signal from the background processes, a sensitivity to the anomalous magnetic moment ${\mathrm{a}}_{\tau }$ = 0 ${}_{+0.011}^{-0.019}$ is obtained at 95\% CL with a dataset corresponding to an integrated luminosity of 2 nb${}^{-1}$ of lead-lead collisions and assuming a conservative 10\% systematic uncertainty. The present results are compared with previous calculations and available measurements.

Comments: 35 pages, 17 Figures Added minor changes on text and some references