Search for lepton-flavor-violating decays of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Z</mml:mi></mml:mrow></mml:math> boson into a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>τ</mml:mi></mml:mrow></mml:math> lepton and a light lepton with the ATLAS detector

Direct searches for lepton flavor violation in decays of the $Z$ boson with the ATLAS detector at the LHC are presented. Decays of the $Z$ boson into an electron or muon and a hadronically decaying $\ensuremath{\tau}$ lepton are considered. The searches are based on a data sample of proton-proton collisions collected by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of $36.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at a center-of-mass energy of $\sqrt{s}=13\text{ }\text{ }\mathrm{TeV}$. No statistically significant excess of events above the expected background is observed, and upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95% confidence level: $\mathcal{B}(Z\ensuremath{\rightarrow}e\ensuremath{\tau})<5.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and $\mathcal{B}(Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau})<2.4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$. This is the first limit on $\mathcal{B}(Z\ensuremath{\rightarrow}e\ensuremath{\tau})$ with ATLAS data. The upper limit on $\mathcal{B}(Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau})$ is combined with a previous ATLAS result based on $20.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of proton-proton collision data at a center-of-mass energy of $\sqrt{s}=8\text{ }\text{ }\mathrm{TeV}$ and the combined upper limit at 95% confidence level is $\mathcal{B}(Z\ensuremath{\rightarrow}\ensuremath{\mu}\ensuremath{\tau})<1.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.