Speaker
Description
The ATLAS experiment has measured the 𝜏-lepton pair production in ultraperipheral lead–lead
collisions, Pb+Pb Pb(𝛾 𝜏𝜏)Pb. From this measurement, constraints on the 𝜏-lepton anomalous magnetic moment, 𝑎𝜏, have been extracted. The used dataset corresponds to an integrated luminosity of 1.44 nb-1` of LHC Pb+Pb collisions at 𝑠NN = 5.02 TeV recorded by the ATLAS experiment in 2018. Selected events contain one muon from a 𝜏-lepton decay, an electron or charged-particle track(s) from the other𝜏-lepton decay, little additional central-detector activity, and no forward neutrons. The 𝛾𝛾𝜏 𝜏
process is observed with a significance exceeding 5 standard deviations, assuming the Standard Model value for 𝑎𝜏. To measure 𝑎𝜏, a template fit to the muon transverse-momentum distribution from 𝜏-lepton candidates is performed, using a dimuon (𝛾𝛾 𝜇𝜇) control sample to constrain systematic uncertainties. The observed 95% confidence-level intervals for 𝑎𝜏 are 𝑎𝜏 (-0.058,-0.012 ) (-0.006. 0.025). These limits are compared with previous 𝑎𝜏 – measurements obtained at LEP and Belle electron-positron colliders.
| Scientific topic | Symmetries and Interactions |
|---|
