A study of the measurement of the $τ$ lepton anomalous magnetic moment in high energy lead-lead collisions at LHC
The $τ$ lepton anomalous magnetic moment: $a_τ= \frac{g_τ-2}{2}$ 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 $a_τ$ 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 $\rm{a_τ}$ = 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.