TY - JOUR
T1 - Observation of the γγ→ττ Process in Pb+Pb Collisions and Constraints on the τ-Lepton Anomalous Magnetic Moment with the ATLAS Detector
AU - ATLAS Publications
AU - Clark, Philip James
AU - Farrington, Sinead
AU - Gao, Yanyan
AU - Leonidopoulos, Christos
AU - Martin, Victoria Jane
AU - Mijovic, Liza
AU - Wynne, Benjamin
AU - Alderweireldt, Sara
AU - Carter, T.M.
AU - Gonzalez Andana, R.Y.
AU - Hasib, A.
AU - Heath, M.P.
AU - Palazzo, S.
AU - Parrish, V.A.
AU - Takeva, E.P.
AU - Themistokleous, N.
AU - Villhauer, E.M.
AU - Zaid, E.
PY - 2023/10/12
Y1 - 2023/10/12
N2 - This Letter reports the observation of τ-lepton-pair production in ultraperipheral lead-lead collisions Pb+Pb→Pb(γγ→ττ)Pb and constraints on the τ-lepton anomalous magnetic moment aτ. The 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 other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations and a signal strength of μττ=1.03+0.06−0.05 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 interval for aτ is −0.057<aτ<0.024.
AB - This Letter reports the observation of τ-lepton-pair production in ultraperipheral lead-lead collisions Pb+Pb→Pb(γγ→ττ)Pb and constraints on the τ-lepton anomalous magnetic moment aτ. The 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 other τ-lepton decay, little additional central-detector activity, and no forward neutrons. The γγ→ττ process is observed in Pb+Pb collisions with a significance exceeding 5 standard deviations and a signal strength of μττ=1.03+0.06−0.05 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 interval for aτ is −0.057<aτ<0.024.
U2 - 10.1103/PhysRevLett.131.151802
DO - 10.1103/PhysRevLett.131.151802
M3 - Article
SN - 0031-9007
VL - 131
SP - 1
EP - 23
JO - Physical Review Letters
JF - Physical Review Letters
IS - 15
M1 - 151802
ER -