Improved estimates of theB(s)→VVdecays in perturbative QCD approach

Abstract

We reexamine the branching ratios, CP -asymmetries, and other observables in a large number of B q → V V (q = u, d, s) decays in the perturbative QCD (PQCD) approach, where V denotes a light vector meson (ρ, K * , ω, φ). The essential difference between this work and the earlier similar works is of parametric origin and in the estimates of the power corrections related to the ratio) (m V and m B denote the masses of the vector and B meson, respectively). In particular, we use up-to-date distribution amplitudes for the final state mesons and keep the terms proportional to the ratio r 2 i in our calculations. Our updated calculations are in agreement with the experimental data, except for a limited number of decays which we discuss. We emphasize that the penguin annihilation and the hard-scattering emission contributions are essential to understand the polarization anomaly, such as in the B → φK * and B s → φφ decay modes. We also compare our results with those obtained in the QCD factorization (QCDF) approach and comment on the similarities and differences, which can be used to discriminate between these approaches in future experiments.

Charmless $$B_{(s)}\rightarrow VV$$ B ( s ) → V V decays in factorization-assisted topological-amplitude approach

“…For the color-suppressed decay mode B 0 → ρ 0 ω, its branching fraction is predicted to be 0.08 × 10 −6 and 0.4 × 10 −6 in QCDF [40] and in PQCD [45], respectively. However, in this work, we predicted its branching ratio to be 1.48 × 10 −6 , which is about 18 times larger than the result of QCDF.…”

“…The experimental data are taken from [58] Decay mode inner quarks, B 0 → ρ 0 ρ 0 has been calculated in perturbative QCD approach in Ref. [45], where they got a rather smaller branching fractions (0.27 × 10 −6 ) and a smaller longitudinal fraction (12%). In fact, there is a large discrepancy between experimental measurements from BaBar and Belle, and the number we quoted in this work is the naive averaged value.…”

“…It will also decrease the predictive power of this FAT approach. As indicated from the QCD factorization approach [41,42] and the perturbative QCD approach [45] calculations, the color-suppressed tree diagram C, W exchange diagram E and the flavorsinglet QCD-penguin diagram S are dominated by longitudinal polarization contributions. For simplicity, we here drop the negligible transverse contributions of these topological diagrams to set χ C = χ ⊥ C = 0, χ E = χ ⊥ E = 0, and χ S = χ ⊥ S = 0.…”

“…Later on, some other penguin-dominated strangeness-changing decays, such as B → ρ K * and B s → φφ, have also been found with large transverse polarization fractions. These large unexpected transverse polarization fractions have attracted much theoretical attention with several explanations based on the QCDF [36][37][38][39][40][41][42], PQCD [43][44][45], even on the new physics scenarios [46][47][48][49][50][51][52][53][54][55]. These decays have rich observables, some of which are regarded as good places for testing the SM and searching for possible effects of new physics beyond the SM.…”

Hadronic decays of B→a1(1260)b1(1235Jing1, Liu2, Xiao3 2017Phys. Rev. DSelf Cite1000View full textAdd to dashboardCite

“…The great efforts have been extensively contributed to the exclusive B → P P, P V, and V V decays at both theoretical and experimental aspects in the past decades, for example, see Refs. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], where P and V denote the S-wave pseudoscalar and vector states, respectively. However, the known "puzzles", for example, the large observed B 0 → π 0 π 0 , B 0 → ρ 0 π 0 , and B → Kη ′ decay rates, the experimental inequality of the direct CP asymmetries between B ± → K ± π 0 and B 0 → K ± π ∓ modes, the unknown mechanism of the polarization in the penguin-dominated B → V V processes etc., are still not elegantly resolved [17][18][19].…”