Abstract
We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay ϒ(3S)→e^{±}μ^{∓} in a sample of 118million ϒ(3S) mesons from 27 fb^{-1} of data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider operating with a 10.36GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[ϒ(3S)→e^{±}μ^{∓}]<3.6×10^{-7} at 90% C. L. This result can be interpreted as a limit Λ_{NP}/g_{NP}^{2}>80 TeV on the energy scale Λ_{NP} divided by the coupling-squared g_{NP}^{2} of relevant new physics (NP).
Highlights
48aINFN Sezione di Roma, I-00185 Roma, Italy 48bDipartimento di Fisica, Universitadi Roma La Sapienza, I-00185 Roma, Italy
We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state
We look for the LFV decay Υð3SÞ → e ± μ∓ in a sample of 118 million Υð3SÞ mesons from 27 fb−1 of data collected with the BABAR detector at the SLAC PEP-II eþe− collider operating with a 10.36 GeV center-of-mass energy
Summary
Searches for electron-tau and muon-tau LFV in decays of bound states of a b quark and b antiquark (bb ) have yielded no evidence of a signal, and upper limits ranging from 3.1 × 10−6 to 6.0 × 10−6 on their branching fractions have been set [3]. The most stringent indirect bound on electron-muon LFV decays of the Υð3SÞ (with mass MΥð3SÞ 1⁄4 10.36 GeV) obtained in this way is B1⁄2Υð3SÞ → e ± μ∓ ≤ 2.5 × 10−8, which uses the reported limit on the branching fraction Bðμ → 3eÞ < 1.0 × 10−12 [5]. The selectors can be deployed to provide different nested levels of particle efficiency and background, from “super loose” (most efficient, least pure) to “super tight” (least efficient, most pure), where candidates selected by tighter criteria of the
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