Measurement of the branching fraction, polarization, and time-dependent CP asymmetry in B0 →ρ ρ- decays and constraint on the CKM angle φ2

I Adachi; L Aggarwal; H Ahmed; N Akopov; M Alhakami; A Aloisio; N Althubiti; N Anh Ky; DM Asner; H Atmacan; V Aushev; M Aversano; R Ayad; V Babu; NK Baghel; P Bambade; S Banerjee; M Barrett; M Bartl; J Baudot; A Baur; A Beaubien; J Becker; JV Bennett; V Bertacchi; M Bertemes; E Bertholet; M Bessner; S Bettarini; B Bhuyan; D Biswas; A Bobrov; D Bodrov; A Bolz; A Bondar; J Borah; A Boschetti; A Bozek; M Bračko; P Branchini; RA Briere; TE Browder; A Budano; S Bussino; Q Campagna; M Campajola; G Casarosa; C Cecchi; J Cerasoli; MC Chang; P Chang; R Cheaib; P Cheema; BG Cheon; K Chilikin; K Chirapatpimol; HE Cho; K Cho; SJ Cho; SK Choi; S Choudhury; J Cochran; 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; F Di Capua; J Dingfelder; Z DoleŽal; I Domínguez Jiménez; TV Dong; X Dong; M Dorigo; D Dossett; K Dugic; G Dujany; P Ecker; J Eppelt; P Feichtinger; T Ferber; T Fillinger; C Finck; G Finocchiaro; A Fodor; F Forti; BG Fulsom; A Gabrielli; E Ganiev; M Garcia-Hernandez; R Garg; G Gaudino; V Gaur; A Gaz; A Gellrich; G Ghevondyan

Journal article

Measurement of the branching fraction, polarization, and time-dependent CP asymmetry in B0 →ρ ρ- decays and constraint on the CKM angle φ2

I Adachi, L Aggarwal, H Ahmed, N Akopov, M Alhakami, A Aloisio, N Althubiti, N Anh Ky, DM Asner, H Atmacan, V Aushev, M Aversano, R Ayad, V Babu, NK Baghel, P Bambade, S Banerjee, M Barrett, M Bartl, J Baudot Show all

Physical Review D | American Physical Society (APS) | Published : 2025

DOI: 10.1103/PhysRevD.111.092001

Abstract

We present a measurement of the branching fraction and fraction of longitudinal polarization of B0→ρ+ρ- decays, which have two π0's in the final state. We also measure time-dependent CP violation parameters for decays into longitudinally polarized ρ+ρ- pairs. This analysis is based on a data sample containing (387±6)×106 ϒ(4S) mesons collected with the Belle II detector at the SuperKEKB asymmetric-energy e+e- collider in 2019-2022. We obtain B(B0→ρ+ρ-)=(2.89-0.22+0.23 -0.27+0.29)×10-5, fL=0.921-0.025+0.024 -0.015+0.017, S=-0.26±0.19±0.08, and C=-0.02±0.12-0.05+0.06, where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysi..

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