CHIPP/CHART Workshop on Sustainability in Particle Physics and CHIPP 2023 plenary

Measurement of the tau g-2 in ultraperipheral PbPb collisions at the CMS experiment

16 Jun 2023, 11:05

15m

Flash talk ECR

Speaker

Arash Jofrehei (University of Zurich (CH))

Description

We present the first observation of $\tau$ lepton pair production in ultraperipheral nucleus-nucleus collisions. The measurement is based on a data sample collected by the CMS experiment at a per nucleon center-of-mass energy of $5.02\mathrm{TeV}$, and corresponding to an integrated luminosity of $404\mu {\mathrm{b}}^{-1}$. The $\gamma \gamma \to {\tau }^{+}{\tau }^{-}$ production is observed with a statistical significance of at least five standard deviations for ${\tau }^{+}{\tau }^{-}$ events with a muon and three charged hadrons in the final state. The cross section is measured in a fiducial phase space region and is found to be $\sigma (\gamma \gamma \to {\tau }^{+}{\tau }^{-})=4.8\pm 0.6(\mathrm{stat})\pm 0.5(\mathrm{syst})\mu \mathrm{b}$, in agreement with leading-order QED predictions. The measurement, based on a small fraction of the expected integrated luminosity of the LHC nuclear program, establishes the potential for an ongoing analysis with substantially more precise determination of the anomalous magnetic moment of the $\tau$ lepton.

Presentation materials

Arash_CHIPP2023.pdf