• Accepted Paper

Polarization fractions and helicity-dependent CP asymmetries in B(s)→ρρ, ρK* and K*K* decays

Jian Chai, Shan Cheng, Feng-Qing Hu, Ya Li, Jin-Yang Shen, and Da-Cheng Yan

Phys. Rev. D - Accepted 2 November, 2026

DOI: https://doi.org/10.1103/qt5g-qyrm

Abstract

In this paper, we present a phenomenological analysis of B(s)→ρρ,ρK* and K*K* decays using state-of-the-art perturbative QCD (pQCD) calculations. Our study is primarily motivated by recent polarization measurements from the LHCb and Belle II collaborations, which have significantly improved the precision of polarization fractions and enabled the first full determination of polarization-dependent CP asymmetries. This work extends the comprehensive pQCD study of charmless two-body B decays reported in our previous paper [Chin. Phys. C 46 (2022) 123103], with a particular focus on polarization observables, especially the CP asymmetries in each helicity state, which reflect distinct orbital angular momentum configurations between the two vector mesons. Our predictions for the branching ratios and longitudinal polarization fractions in the B0→K*0K‾*0 and B+→ρ0K*+ modes are in good agreement with the new experimental data. However, the calculated longitudinal polarization fraction for Bs→K*0K‾*0 is significantly larger than the LHCb measurement. Moreover, the predicted (helicity-dependent) CP asymmetries in B+→ρ0K*+ are about 30% smaller than the observed values. These discrepancies point to a rich interplay between different topological amplitudes, highlighting the need for further theoretical investigation to resolve the long-standing polarization puzzle in two-body B decays into vector mesons.

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