Searches for charged-lepton-flavor violation in ${\chi }_{bJ}(1P)$ decays

Abstract

We report the first searches for charged-lepton-flavor violation in decays of ${\chi }_{bJ}(1P)$ ($J=0,1,$ and $2$) to a pair of charged leptons using 158 million ${\rm Y}(2S)$ decays collected with the Belle detector in $e^{+}{e}^{-}$ collisions at the KEKB collider. No significant signal is observed, and we set upper limits on the branching fractions for ${\chi }_{bJ}(1P)$ decays to $e^{\pm }{\mu }^{\mp }$ at the level of $10^{-6}$ and to $e^{\pm }{\tau }^{\mp }$ or ${\mu }^{\pm }{\tau }^{\mp }$ at the level of $10^{-5}$. Limits on ${\chi }_{b0}(1P)$ decays are translated into bounds on the corresponding Wilson coefficients of scalar operators that mediate charged-lepton-flavor violation.

5 pages, 4 figures, HQL 2025, QWG 2025

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