Search for the charged-lepton-flavor-violating decay $Z\to e\mu$ in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Abstract

A search for the charged-lepton-flavor-violating process $Z\to e\mu$ is presented, using 139 fb${}^{-1}$ of $\sqrt{s}=13$ TeV $pp$ collision data collected by the ATLAS experiment at the LHC. An excess in the $e\mu$ invariant mass spectrum near the $Z$ boson mass would be a striking signature of new physics. No excess is observed, and an upper limit $B(Z\to e\mu )<2.62\times 10^{-7}$ is placed on the branching fraction at 95% confidence level, which is the most stringent limit to date.

arXiv comment33 pages in total, author list starting on page 16, 2 figures, 3 tables, published in Phys. Rev. D (https://link.aps.org/doi/10.1103/PhysRevD.108.032015). All figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2018-35/

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