Searches for Charged-Lepton-Flavor Violation in χbJ (1P) Decays

M Abumusabh; I Adachi; A Aggarwal; L Aggarwal; H Ahmed; Y Ahn; H Aihara; N Akopov; S Alghamdi; M Alhakami; A Aloisio; N Althubiti; K Amos; M Angelsmark; N Anh Ky; C Antonioli; DM Asner; H Atmacan; T Aushev; R Ayad; V Babu; H Bae; NK Baghel; S Bahinipati; P Bambade; S Banerjee; M Barrett; M Bartl; J Baudot; A Baur; A Beaubien; F Becherer; J Becker; JV Bennett; FU Bernlochner; V Bertacchi; M Bertemes; E Bertholet; M Bessner; S Bettarini; V Bhardwaj; F Bianchi; T Bilka; D Biswas; A Bobrov; D Bodrov; A Bondar; G Bonvicini; J Borah; A Boschetti; A Bozek; M Bračko; P Branchini; RA Briere; TE Browder; A Budano; S Bussino; Q Campagna; M Campajola; L Cao; G Casarosa; C Cecchi; MC Chang; P Chang; P Cheema; L Chen; BG Cheon; C Cheshta; H Chetri; K Chilikin; K Chirapatpimol; HE Cho; K Cho; SJ Cho; SK Choi; S Choudhury; S Chutia; J Cochran; JA Colorado-Caicedo; I Consigny; L Corona; JX Cui; E De La Cruz-Burelo; SA De La Motte; G De Nardo; G De Pietro; R De Sangro; M Destefanis; S Dey; R Dhayal; A Di Canto; J Dingfelder; Z DoleŽal; I Domínguez Jiménez; TV Dong; X Dong; G Dujany; P Ecker; D Epifanov; J Eppelt

Journal article

Searches for Charged-Lepton-Flavor Violation in χbJ (1P) Decays

M Abumusabh, I Adachi, A Aggarwal, L Aggarwal, H Ahmed, Y Ahn, H Aihara, N Akopov, S Alghamdi, M Alhakami, A Aloisio, N Althubiti, K Amos, M Angelsmark, N Anh Ky, C Antonioli, DM Asner, H Atmacan, T Aushev, R Ayad Show all

Physical Review Letters | American Physical Society (APS) | Published : 2026

DOI: 10.1103/1rj5-2wvr

Open access

Abstract

We report the first searches for charged-lepton-flavor violation in decays of χbJ(1P) (J=0, 1, and 2) to a pair of charged leptons using 158 million ϒ(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 χbJ(1P) decays to e±μ∓ at the level of 10-6 and to e±τ∓ or μ±τ∓ at the level of 10-5. Limits on χb0(1P) decays are translated into bounds on the corresponding Wilson coefficients of scalar operators that mediate charged-lepton-flavor violation.