A search for an excited muon decaying to a muon and two jets in $pp$ collisions at $\sqrt{s}$ = 8 TeV with the ATLAS detector

Abstract

A new search signature for excited leptons is explored. Excited muons are sought in the channel $pp\to \mu {\mu }^{\ast }\to \mu \mu \text{ jet jet}$, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb${}^{-1}$ of $pp$ collision data at a centre-of-mass energy of $\sqrt{s}$ = 8 TeV taken with the ATLAS detector at the Large Hadron Collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass $m_{{\mu }^{\ast }}$. For $m_{{\mu }^{\ast }}$ between 1.3 TeV and 3.0 TeV, the upper limit on $\sigma B({\mu }^{\ast }\to \mu q\bar{q}$) is between 0.6 and 1 fb. Limits on $\sigma B$ are converted to lower bounds on the compositeness scale $\Lambda$. In the limiting case $\Lambda =m_{{\mu }^{\ast }}$, excited muons with a mass below 2.9 TeV are excluded. With the same model assumptions, these limits at larger ${\mu }^{\ast }$ masses improve upon previous limits from traditional searches based on the gauge-mediated decay ${\mu }^{\ast }\to \mu \gamma$.

33 pages in total, author list starting page 16, 4 figures, 5 tables, final version published by New Journal of Physics including corrections in Erratum https://dx.doi.org/10.1088/1367-2630/ab46ed. All figures including auxiliary are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2015-01

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Cited by in corpus (4)

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• Search for an excited lepton that decays via a contact interaction to a lepton and two jets in proton-proton collisions at $\sqrt{s}=$ 13 TeV