The ATLAS detector at the Large Hadron Collider is used to search for the lepton flavor violating process $Z\to e\mu$ in $pp$ collisions using $20.3{\mathrm{fb}}^{-1}$ of data collected at $\sqrt{s}=8\mathrm{TeV}$. An enhancement in the $e\mu$ invariant mass spectrum is searched for at the $Z$-boson mass. The number of $Z$ bosons produced in the data sample is estimated using events of similar topology, $Z\to ee$ and $\mu \mu$, significantly reducing the systematic uncertainty in the measurement. There is no evidence of an enhancement at the $Z$-boson mass, resulting in an upper limit on the branching fraction, $\mathcal{B}(Z\to e\mu )<7.5\times 10^{-7}$ at the 95% confidence level.

• Received 26 August 2014

DOI:https://doi.org/10.1103/PhysRevD.90.072010

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© 2014 CERN, for the ATLAS Collaboration