分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： Within the factorization-assisted topological-amplitude approach, we study the two-body charmed B meson decays Bu,d,s→D(∗)M, with M denoting a light pseudoscalar (or vector) meson. The meson decay constants and transition form factors are factorized out from the hadronic matrix element of topological diagrams. Therefore the effect of SU(3) symmetry breaking is retained, which is different from the conventional topological diagram approach. The number of free nonperturbative parameters to be fitted from experimental data is also much less. Only four universal nonperturbative parameters χC, ϕC, χE and ϕE are introduced to describe the contribution of the color suppressed tree and W-exchanged diagrams for all the decay channels. With the fitted parameters from 31 decay modes induced by b→c transition, we then predict the branching fractions of 120 decay modes induced by both b→c and b→u transitions. Our results are well consistent with the measured data or to be tested in the LHCb and Belle-II experiments in the future. Besides, the SU(3) symmetry breaking, isospin violation and CP asymmetry are also investigated.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We study S-wave resonance contributions to the B0(s)→J/ψπ+π− and Bs→π+π−ℓ+ℓ− decays in the perturbative QCD (PQCD) framework by introducing two-hadron distribution amplitudes for final states. The Breit-Wigner formula for the f0(500), f0(1500) and f0(1790) resonances and the Flatt\'e model for the f0(980)resonance are adopted to parameterize the time-like scalar form factors in the two-pion distribution amplitudes, which include both resonant and nonresonant contributions. The resultant branching fraction and differential branching fraction in the pion-pair invariant mass for each resonance channel are consistent with experimental data. The determined S-wave two-pion distribution amplitudes, containing the information of both resonant and nonresonant rescattering phases, can be employed to predict direct CP asymmetries of other three-body hadronic B meson decays in various localized regions of two-pion phase space.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： Within the QCD factorization approach, we calculate the branching fractions and CP asymmetry parameters of 12 B→K∗0(1430)K(∗) decay modes under the assumption that the scalar meson K∗0(1430) is the first excited state or the lowest lying ground state in the quark model. We find that the decay modes with the scalar meson emitted, have large branching fractions due to the enhancement of large chiral factor rK∗0χ. The branching fractions of decays with the vector meson emitted, become much smaller owing to the smaller factor rK∗χ. Moreover, the annihilation type diagram will induce large uncertainties because of the extra free parameter dealing with the endpoint singularity. For the pure annihilation type decays, our predictions are smaller than that from PQCD approach by 2-3 orders of magnitudes. These results will be tested by the ongoing LHCb experiment, forthcoming Belle-II experiment and the proposing circular electron-positron collider.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： We reexamine the branching ratios, CP-asymmetries, and other observables in a large number of Bq→VV(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 r2i=m2Vi/m2B(i=2,3) (mV and mB 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 r2i 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 Bs→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.
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