Study of the measurement of the τ lepton anomalous magnetic moment in high energy lead-lead collisions at the LHC

The z lepton anomalous magnetic moment a z = gz-2 z -2 2 was measured, so far, with a precision of only several percents, despite its high sensitivity to physics beyond the Standard Model such as compositeness or supersymmetry. A new study is presented to improve the sensitivity of the a z measurement with photon- photon interactions from ultraperipheral lead-lead collisions at the LHC. The theoretical approach used in this work is based on an effective Lagrangian and on a photon flux implemented in the M ad G raph5 Monte Carlo simulation. Using a multivariate analysis to discriminate the signal from the background processes, a sensitivity to the anomalous magnetic moment a z = 0 -0.019 & thorn; 0.015 is obtained at 95% confidence level with a dataset corresponding to an integrated luminosity of 2 nb-1 - 1 of lead-lead collisions and assuming a conservative 10% systematic uncorrelated uncertainty for signal and background. The present results using multivariate analysis are compared to similar results obtained using sequential cuts, as done in previous measurements, showing an improvement of about 35% in the sensitivity to a z .