Abstract
Within the framework of the perturbative quantum chromodynamics (PQCD) approach, we study the charmless two-body decays B→a1(1260)K*, b1(1235)K*. Using the decay constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results. (a) Our predictions for the branching ratios are consistent with the QCD factorization (QCDF) results within errors, but much larger than the naive factorization approach calculation values. (b) We predict that the anomalous polarizations occurring in the decays B→φK*, $rHK* also happen in B→a1K* decays, while they do not happen in B→b1K* decays. Here the contributions from the annihilation diagrams play an important role in explaining the larger transverse polarizations in the B→a1K* decays, while they are not sensitive to the polarizations for the B→b1K* decays. (c) Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays B̄0 → b+1K*−, B− → b01K*− have larger direct CP-asymmetries, which could be measured by the present LHCb experiment and the forthcoming Super-B experiment.
Highlights
The mesons are classified in JP C multiplets
In many B → V V decays, the information on branching ratios and polarization fractions among various helicity amplitudes have been studied by many authors [1,2,3,4]
We know that a1(1260) has some similar behaviors as the vector meson, so one can expect that there should exist some similar characteristics in the branching ratios and the polarization fractions between the decays B → a1(1260)K∗ and B → ρK∗, where a1(1260) and ρ are scalar partners of each other, while this is not the case for b1(1235) because of its different characteristics in the decay constant and light-cone distribution amplitude (LCDA) compared with those of a1(1260)
Summary
The mesons are classified in JP C multiplets. There are two types of orbitally excited axial-vector mesons, namely, 1++ and 1+−. In many B → V V decays, the information on branching ratios and polarization fractions among various helicity amplitudes have been studied by many authors [1,2,3,4]. We know that a1(1260) has some similar behaviors as the vector meson, so one can expect that there should exist some similar characteristics in the branching ratios and the polarization fractions between the decays B → a1(1260)K∗ and B → ρK∗, where a1(1260) and ρ are scalar partners of each other, while this is not the case for b1(1235) because of its different characteristics in the decay constant and light-cone distribution amplitude (LCDA) compared with those of a1(1260). The longitude decay constant is very small for the charged b1(1235) states and vanishes under the SU(3) limit.
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