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Register a new userFactorization and polarization in two charmed-meson B decays
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We provide a comprehensive test of factorization in the heavy-heavy $B$ decays motivated by the recent experimental data from BELLE and BABAR collaborations. The penguin effects are not negligible in the B decays with two pseudoscalar mesons. The direct CP asymmetries are found to be a few percent. We give estimates on the weak annihilation contributions by analogy to the observed annihilation-dominated processes. The $N_c$ insensitivity of branching ratios indicates that the soft final state interactions are not dominant. We also study the polarizations in $Bto D^*D_{(s)}^*$ decays. The power law shows that the transverse perpendicular polarization fraction is small. The effects of the heavy quark symmetry breaking caused by the perturbative QCD and power corrections on the transverse polarization are also investigated.
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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.
We analyze the quasi-two-body charmed $B$ decays $B^{+,0}_{(s)} to D_{(s)}^* P_2 to D_{(s)} P_1 P_2$ with $P_{1,2}$ as a pion or kaon. The intermediate processes $B_{(s)} to D_{(s)}^* P_2 $ are calculated with the factorization-assisted topological-amplitude approach and the resonant effects are calculated with the Breit-Wigner formalism. Taking all p-wave resonance states $ bar D_{(s)}^*$ into consideration, we present the related branching fractions, calculate the Breit-Wigner-Tail effects, and investigate the flavor $SU(3)$ breaking effects. Most of our branching fractions are consistent with the perturbative QCD approachs predictions as well as the current experimental data. With more precision calculation of the intermediate two body charmed B meson decays, our quasi-two-body B decays calculation has significantly less theoretical uncertainty than the perturbative QCD approach. Many of those channels without any experimental data will be confronted with the future more accurate experiment measurements. Our results of the Breit-Wigner-tail effects also agree with the experimental very well. In $B^0$ decays this effect can reach approximately to $5%$. It is also found that the Breit-Wigner-tail effects are not sensitive to the widths of their corresponding resonances. The flavor $SU(3)$ symmetry breaking effect is also investigated.
This article summarizes recent developments in $Bto D^{(ast)}tau u$ decays. We explain how to extract the tau leptons production properties from the kinematics of its decay products. The focus is on hadronic tau decays, which are most sensitive to the tau polarizations. We present new results for effects of new physics in tau polarization observables and quantify the observation prospects at BELLE II.
Using methods of effective field theory, factorized expressions for arbitrary B -> X_u l nu decay distributions in the shape-function region of large hadronic energy and moderate hadronic invariant mass are derived. Large logarithms are resummed at next-to-leading order in renormalization-group improved perturbation theory. The operator product expansion is employed to relate moments of the renormalized shape function with HQET parameters such as m_b, Lambda(bar) and lambda_1 defined in a new physical subtraction scheme. An analytic expression for the asymptotic behavior of the shape function is obtained, which reveals that it is not positive definite. Explicit expressions are presented for the charged-lepton energy spectrum, the hadronic invariant mass distribution, and the spectrum in the hadronic light-cone momentum P_+ = E_H - P_H. A new method for a precision measurement of |V_{ub}| is proposed, which combines good theoretical control with high efficiency and a powerful discrimination against charm background.
In QCD the amplitude for B0 -> D(*)+pi- factorizes in the large Nc limit or in the large energy limit Q >> Lambda_QCD where Q = {m_b, m_c, m_b-m_c}. Data also suggests factorization in exclusive processes B-> D* pi+ pi- pi- pi0 and B-> D* omega pi-, however by themselves neither large Nc nor large Q can account for this. Noting that the condition for large energy release in B0-> D+ pi- is enforced by the SV limit, m_b, m_c >> m_b-m_c >> Lambda, we propose that the combined large Nc and SV limits justify factorization in B -> D(*) X. This combined limit is tested with the inclusive decay spectrum measured by CLEO. We also give exact large Nc relations among isospin amplitudes for B -> D(*)X and B -> D(*) D-bar(*)X, which can be used to test factorization through exclusive or inclusive measurements. Predictions for the modes B-> D(*) pi pi, B-> D(*)K K-bar and B-> D(*) D-bar(*) K are discussed using available data.
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