Polarization fractions and helicity-dependent CP asymmetries in B_(s) → ρρ, ρK^∗ and K^∗ K^∗ decays

@misc{chai2026polarization,
  title = {{Polarization fractions and helicity-dependent CP asymmetries in $B_(s) \to ρρ, ρK^\ast$ and $K^\ast K^\ast$ decays}},
  author = {Jian Chai and Shan Cheng and Feng-Qing Hu and Ya Li and Jin-Yang Shen and Da-Cheng Yan},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2607.22093},
  eprint = {2607.22093},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2607.22093},
}

TY  - UNPB
TI  - Polarization fractions and helicity-dependent CP asymmetries in B_(s) → ρρ, ρK^∗ and K^∗ K^∗ decays
AU  - Jian Chai
AU  - Shan Cheng
AU  - Feng-Qing Hu
AU  - Ya Li
AU  - Jin-Yang Shen
AU  - Da-Cheng Yan
PY  - 2026
DA  - 2026/11/03
PB  - arXiv
DO  - 10.48550/arxiv.2607.22093
UR  - https://arxiv.org/abs/2607.22093
AB  - 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 B^0 → K^∗ 0 K̅^∗ 0 and B^+ → ρ^0 K^∗ + modes are in good agreement with the new experimental data. However, the calculated longitudinal polarization fraction for B_s → K^∗ 0 K̅^∗ 0 is significantly larger than the LHCb measurement. Moreover, the predicted (helicity-dependent) CP asymmetries in B^+ → ρ^0 K^∗ + 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.
ER  -