# Search for lepton-flavour-violating decays of the $Z$ boson into a $\tau$-lepton and a light lepton with the ATLAS detector

### Submission summary

 Authors (as Contributors): Wing Sheung Chan
Submission information
Date accepted: 2019-01-17
Date submitted: 2018-12-07 01:00
Submitted by: Chan, Wing Sheung
Submitted to: SciPost Physics Proceedings
Proceedings issue: The 15th International Workshop on Tau Lepton Physics (Amsterdam, 2018-09)
Ontological classification
Specialties:
• High-Energy Physics - Experiment
Approach: Experimental

### Abstract

Lepton flavour violation in the charged lepton sector is an unambiguous signal of physics beyond the Standard Model. Searches for lepton flavour violation in decays of the $Z$ boson with the ATLAS detector is reported, focusing on decays into an electron or muon and a hadronically decaying $\tau$-lepton, using $pp$ collisions data with a centre-of-mass energy of 13 TeV. Upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95\% confidence level: $\mathcal{B}(Z\to e\tau) < 5.8\times10^{-5}$ and $\mathcal{B}(Z\to \mu\tau) < 2.4\times10^{-5}$. When combined with a previous ATLAS result based on $pp$ collisions data with a centre-of-mass energy of 8 TeV, an upper limit of $\mathcal{B}(Z\to \mu\tau) < 1.3\times10^{-5}$ is obtained.

Published as SciPost Phys. Proc. 1, 048 (2019)