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 analysis to constrain the Cabibbo-Kobayashi-Maskawa angle φ2 and obtain two solutions; the result consistent with other Standard Model constraints is φ2=(92.6-4.7+4.5)°.

Measurement of the branching fraction, polarization, and time-dependent CP asymmetry in B0 →ρ+ρ- decays and constraint on the CKM angle φ2 / Adachi, I., Aggarwal, L., Ahmed, H., Akopov, N., Alhakami, M., Aloisio, A., Althubiti, N., Anh Ky, N., Asner, D. m., Atmacan, H., Aushev, V., Aversano, M., Ayad, R., Babu, V., Baghel, N. k., Bambade, P., Banerjee, Sw., Barrett, M., Bartl, M., Baudot, J., et al.. - In: PHYSICAL REVIEW D. - ISSN 2470-0010. - 111:9(2025), pp. 092001.1-092001.15. [10.1103/physrevd.111.092001]

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

Dorigo, M.;Gabrielli, A.;Ganiev, E.;Ghosh, D.;Lanceri, L.;Manfredi, R.;Mantovano, M.;Raiz, S.;Vitale, L.;
2025-01-01

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 analysis to constrain the Cabibbo-Kobayashi-Maskawa angle φ2 and obtain two solutions; the result consistent with other Standard Model constraints is φ2=(92.6-4.7+4.5)°.
2025
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11368/3121584
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