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Register a new userA Novel PQCD Approach in Charmless B-meson Decays
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We discuss a novel pertubative QCD approach on the exclusive non-leptonic two body B-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approaches. We show numerical results which is compatible with recent experimantal data for the charmless B-meson decays.
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New physics contributions to B decays often arise through chromo-magnetic penguin operators. To look for new physics effects in B decays, it is useful to be able to estimate the hadronic matrix elements for the chromo-magnetic operator. We compute this contribution to B ->phi K decays using PQCD methods. It is shown that, if the Wilson coefficient of the new physics is same order of magnitude as that of the Standard Model, this operator gives a non-negligible contribution compared to that of the Standard Model (about 30%). We also investigate the value of q^2, which is the momentum transferred by the gluon in the chromo-magnetic penguin operator. We find that the expectation value <q^2> is approximately M^2_B/4, in agreement with a naive guess. This result, however, is very sensitive to the scale dependence of the Wilson coefficient. We also show that the matrix element for the chromo-magnetic penguin operator is independent of the choice of energy scale to a very good approximation.
We study the effects of the MSSM contribution on B -> phi K decays using the perturbative QCD approach. In this approach, strong phases can be calculated, so that we can predict the values of CP asymmetries with the MSSM contribution. We predict a large relative strong phase between the penguin amplitude and the chromomagnetic penguin amplitude. If there is a new CP violating phase in the chromomagnetic penguin amplitude, then the CP asymmetries may change significantly from the SM prediction. We parametrize the new physics contributions that appear in the Wilson coefficients. We maximize the new physics parameters up to the point where it is limited by experimental constraints. In the case of the LR insertion, we find that the direct CP asymmetries can reach about 85% and the indirect CP asymmetry can reach about -30%.
We review the two and three-body baryonic $B$ decays with the dibaryon (${bf Bbar B}$) as the final states. Accordingly, we summarize the experimental data of the branching fractions, angular asymmetries, and $CP$ asymmetries. In the approach of perturbative QCD counting rules, we study the three-body decay channels. Using the $W$-boson annihilation (exchange) mechanism, the branching fractions of $Bto {bf B bf bar B}$ are shown to be interpretable. In particular, we review the $CP$ asymmetries of $Bto {bf Bbar B}M$, which are promising to be measured by the LHCb and Belle II experiments.
B meson semileptonic decays are a crucial tool in our studies of the quark mixing parameters Vcb and Vub. The interplay between experimental and theoretical challenges to achieve precision in the determination of these fundamental parameters is discussed.
We report on preliminary measurements of branching fractions, charge-parity-violating asymmetries, and longitudinal polarization fractions in charmless bottom-meson decays from the Belle~II experiment. We use samples of electron-positron collisions collected in 2019 and 2020 at the $Upsilon(4S)$ resonance, corresponding to integrated luminosities of up to 62.8 ${rm fb^{-1}}$. The results are compatible with known values, indicating good understanding of early detector performance.
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