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The spectra and wave functions of heavy-light mesons are calculated within a relativistic quark model, which is based on a heavy-quark expansion of the instantaneous Bethe-Salpeter equation by applying the Foldy-Wouthuysen transformation. The kernel we choose is the standard combination of linear scalar and Coulombic vector. The effective Hamiltonian for heavy-light quark-antiquark system is calculated up to order $1/m_Q^2$. Our results are in good agreement with available experimental data except for the anomalous $D_{s0}^*(2317)$ and $D_{s1}(2460)$ states. The newly observed heavy-light meson states can be accommodated successfully in the relativistic quark model with their assignments presented. The $D_{sJ}^*(2860)$ can be interpreted as the $|1^{3/2}D_1\rangle$ and $|1^{5/2}D_3\rangle$ states being members of the 1D family with $J^P=1^-$ and $3^-$., Comment: 13 pages, 2 tables, 4 figures

We review the perturbative QCD approach study of hadronic B decays. Utilizing the constrained parameters in these well measured decay channels, we study most of the possible charmless $B_s \to PP$, $PV$ and $VV$ decay channels in the perturbative QCD approach. In addition to the branching ratios and CP asymmetries, we also give predictions to the polarization fractions of the vector meson final states. The size of SU(3) breaking effect is also discussed. These predictions can be tested by the future LHCb experiment., Comment: 5 pages, talk given at Flavor Physics & CP Violation Conference, Taipei, 2008 and The 4th International Conference on Flavor Physics Sep. 24, 2007, Beijing

The perturbative QCD approach is based on $k_T$ factorization, including the Sudakov form factors so that to avoid the endpoint singularity. In this approach, we calculate the charmless B decays like $B\to \pi\pi$ decays etc. to produce the right number of branching ratios and also CP asymmetry parameters. For final states with at least one charmed meson, like $B\to D\pi$ decays, our results also agree with the experiments., Comment: 7 pages, with 1 figure, proceedings of the International Conference On Nonperturbative Quantum Field Theory: Lattice And Beyond, 18-20 Dec 2004, Guangzhou, Canton, China

We study the rare radiative dileptonic decays $B^0(B_s)\to \gamma\ell^+\ell^-$ ($\ell=e,\mu$) in the standard model. By using the $B$ meson wave function constrained by non-leptonic decays, the branching ratios turn out to be of the order of $10^{-9}$ for $B_s\to\gamma\mu^+\mu^-$, $\gamma e^+ e^-$ and $10^{-10}$ for $B^0\to\gamma\mu^+\mu^-$, $\gamma e^+ e^-$. Based on the study, these decays are accessible at the near future LHC-b experiment, which are useful to determine the $B(B_s)$ wave function.

There are different approaches for the hadronic B decay calculations, recently. In this paper, we upgrade three of them, namely factorization, QCD factorization and the perturbative QCD approach based on $k_T$ factorization, by using new parameters and full wave functions. Although they get similar results for many of the branching ratios, the direct CP asymmetries predicted by them are different, which can be tested by recent experimental measurements of B factories., 11 pages, 3 figures, revtex4, Talk given at the Workshop on the Frontiers of Theoretical Physics and Cross-Disciplinary, NSFC, Beijing, March 2005

We investigate the branching ratios and direct CP asymmetries of $B_c^+\to D^0\pi^+$ and $B_c^+\to D^+\pi^0$ decays in the PQCD approach. All the diagrams with emission topology or annihilation topology are calculated strictly. A branching ratio of $10^{-6}$ and $10^{-7}$ for $B_c^+\to D^0\pi^+$ and $B_c^+\to D^+\pi^0$ decay is predicted, respectively. Because of the different weak phase and strong phase from penguin operator and two kinds of tree operator contributions, we predict a possible large direct CP violation: $A^{\rm dir}_{cp} (B_c^\pm \to D^0 \pi^\pm)\approx -50%$ and $A^{\rm dir}_{cp} (B_c^\pm \to D^\pm \pi^0)\approx 25%$ when $\gamma=55^\circ$, which can be tested in the coming LHC.

In this work, we calculate the rare decays $B^0 \to D_s^{*-} K^+$ and $B^+ \to D_s^{*+} \bar{K}^0$ in perturbative QCD approach with Sudakov resummation. We give the branching ratio of $10^{-5}$ for $B^0 \to D_s^{*-}K^+$, which will be tested soon in $B$ factories. The decay $B^+ \to D_s^{*+} \bar{K}^0$ has a very small branching ratio at ${\cal O}(10^{-8})$, due to the suppression from CKM matrix elements $|V_{ub}^* V_{cd}|$. It may be sensitive to new physics contributions.

In this work, we investigate the radiative leptonic decays D_(s)^- \to \gamma \ell \bar\nu (\ell = e, \mu) at tree level within the non-relativistic consistuent quark model and the effective Lagrangian for the heavy flavor decays. We find that the contributions for the three Feynman diagrams are all important. With the full calculation, the decay branching ratios are of the order of 10^-5 for D_s^- \to \gamma \ell \bar\nu and 10^-6 for D^- \to \gamma \ell \bar\nu, respectively. These decays can be measured at B factories and future CLEO-C experiments to determine the decay constants f_D_s and f_D.

With the fresh experimental bounds of b → sγ issued by CLEO and the value of the top-quark mass by CDF and D0, the constraints on the two Higgs doublet models (2HDM) are re-examined. In the examination an effective Lagrangian is used, which contains all of the energy scale evolution not only from the W boson mass to the bottom-quark mass but also from the top-quark mass to W boson mass for the QCD corrections. As a result, it is implied that the constraint on the mass of the charged Higgs boson emerging in the concerned models turns to be more stringent than that achieved by the earlier analyses.

We give a more complete calculation of $b \to s e^+e^- $ decay including leading log QCD corrections from $m_{top}$ to $M_W$ in addition to corrections from $M_{W}$ to $m_b$. The differential decay rate is found to be slightly suppressed for a large invariant mass of the $e^+e^- $ pair; while the integrated width is slightly enhanced comparing with the results without the QCD running from $m_{top}$ to $M_W$.

We study the loop induced rare decays $B_s(B_d)\to\gamma\nu\bar\nu$ within the standard model. Both constituent quark model and pole model are used and the branching ratios turn out to be of the orders of $10^{-8}$ for $B_s\to \gamma \nu \bar \nu $ and $10^{-9}$ for $B_d \to \gamma \nu \bar \nu $. These processes can be served to determine the decay constants of $B_s$ and $B_d$.

We introduce an anomalous top quark coupling (right-handed current) into the standard model Lagrangian. Based on this, a more complete calculation of {ital b}{r_arrow}{ital s}{gamma} decay including leading log QCD corrections from {ital m}{sub {ital t}} to {ital M}{sub {ital W}} in addition to corrections from {ital M}{sub {ital W}} to {ital m}{sub {ital b}} is given. The inclusive decay rate is found to be suppressed compared with the case without QCD running from {ital m}{sub {ital t}} to {ital M}{sub {ital W}} except at the time of small values of {vert_bar}{ital f}{sub {ital R}}{sup {ital t}{ital b}}{vert_bar}. For example, when {ital f}{sub {ital R}}{sup {ital t}{ital b}}={minus}0.08, it is only 1/10 of the value given before. As {vert_bar}{ital f}{sub {ital R}}{sup {ital t}{ital b}}{vert_bar} gets smaller, this contribution is an enhancement as in the standard model case. From the new experiment of the CLEO Collaboration, strict restrictions to parameters of this top-bottom quark coupling are found.

We give a more complete calculation of $b \to s\gamma $ decay in 2-Higgs doublet model, including leading log QCD corrections from $m_{top}$ to $M_W$ in addition to corrections from $M_{W}$ to $m_b$. The inclusive decay rate in the first model is found to be suppressed 23\% comparing with the calculations without the QCD running from $m_{top}$ to $M_W$. And the enhancement up to 5\% is found in calculations of the second model. More strict restrictions to parameters of 2-Higgs doublet model II are found.

model-independent way to distinguish the descriptions for light scalar mesons . It also applies to the B− → Sl−ν and B0 → J/ψ(ηc)S decays. The SU(3) symmetry breaking effect is found to be under control, which will not spoil our method. The branching fractions of the D+ → Sl+ν , B−→ Sl−ν and B0→ J/ψ(ηc)S decays roughly have the order 10−4, 10−5 and 10−6, respectively. The B factory experiments and ongoing BEPC-II experiments are able to measure these channels

In the SU(3) symmetry limit, the ratio $R\equiv\frac{{\cal B}(D^+\to f_0l^+\nu)+ {\cal B}(D^+\to \sigma l^+\nu)}{{\cal B}(D^+\to a_0^0l^+\nu)}$ is equal to 1 if the scalar mesons are $\bar qq$ states, while it is 3 if these mesons are tentraquark states. This ratio provides a model-independent way to distinguish the descriptions for light scalar mesons . It also applies to the $B^-\to Sl^-\bar\nu$ and $\bar B^0\to J/\psi(\eta_c) S$ decays. The SU(3) symmetry breaking effect is found to be under control, which will not spoil our method. The branching fractions of the $D^+\to S l^+\nu$, $B^-\to S l^-\bar\nu$ and $\bar B^0\to J/\psi(\eta_c) S$ decays roughly have the order $10^{-4}$, $10^{-5}$ and $10^{-6}$, respectively. The B factory experiments and ongoing BEPC-II experiments are able to measure these channels and accordingly to provide the detailed information of the scalar meson inner structure., Comment: 5 pages, talk given at 45th Rencontres de Moriond QCD and High Energy Interactions, March 2010, La Thuile and XIII International Conference on Hadron Spectroscopy, Florida, 2009

In this work we use the heavy-quark-light-diquark picture to study the semileptonic decay {lambda}{sub b}{yields}{lambda}{sub c}+l+{nu}{sub l} in the so-called hybrid scheme. Namely, we apply the heavy quark effective theory (HQET) for larger q{sup 2} (corresponding to small recoil), which is the invariant mass square of l+{nu}, whereas the perturbative QCD approach for smaller q{sup 2} to calculate the form factors. The turning point where we require the form factors derived in the two approaches to be connected, is chosen near {rho}{sub cut}=1.1. It is noted that the kinematic parameter {rho} which is usually adopted in the perturbative QCD approach, is in fact exactly the same as the recoil factor {omega}=v{center_dot}v{sup '} used in HQET where v, v{sup '} are the four velocities of {lambda}{sub b} and {lambda}{sub c} respectively. We find that the final result is not very sensitive to the choice, so that it is relatively reliable. Moreover, we apply a proper numerical program within a small range around {rho}{sub cut} to make the connection sufficiently smooth and we parametrize the form factor by fitting the curve gained in the hybrid scheme. The expression and involved parameters can be compared with the ones gained by fitting the experimentalmore » data. In this scheme the end-point singularities do not appear at all. The calculated value is satisfactorily consistent with the data which is recently measured by the DELPHI collaboration within 2 standard deviations.« less

We study the rare decays B{sub s}{sup 0}{yields}D{sup {+-}}{pi}{sup {+-}} and B{sub s}{sup 0}{yields}D{sup {+-}}{pi}{sup {+-}}, which can occur only via annihilation type W exchange diagrams in the standard model. The time-dependent decay rates of the four channels can provide four CP parameters, which are experimentally measurable. We show that the Cabibbo-Kobayashi-Maskawa angle {phi}{sub 3}={gamma} can be determined from these parameters without any theoretical model dependence. These channels can be measured in future LHCb experiments to provide a clean way for {gamma} measurement.

The rare decays B-0 --> D-s(-) K+ and B+ --> D-s(+)(K) over bar (0) can occur only via annihilation type diagrams in the standard model. We calculate these decays in the perturbative QCD approach. We found that the calculated branching ratio of B-0 --> Ds-K+ agreed with the data which had been observed in the KEK and SLAC B factories. The decay B+ --> D-s(+)(K) over bar (0) has a very small branching ratio at O(10(-8)), due to the suppression from the CKM matrix elements \V-ub* V-cd\.

The rare decays $B^0 \to D_s^- K^+$ and $B^+ \to D_s^+ \bar{K}^0$ can occur only via annihilation type diagrams in the standard model. We calculate these decays in perturbative QCD approach. We found that the calculated branching ratio of $B^0 \to D_s^- K^+$ agreed with the data which had been observed in the KEK and SLAC $B$ factories. While the decay $B^+ \to D_s^+ \bar{K}^0$ has a very small branching ratio at ${\cal O}(10^{-8})$, due to the suppression from CKM matrix elements $|V_{ub}^* V_{cd}|$., Comment: 18 pages, 3 figures

The rare decay $B^+ \to D_s^+ \phi$ can occur only via annihilation type diagrams in the standard model. We calculate this decay in perturbative QCD approach with Sudakov resummation. We found that the branching ratio of $B^+ \to D_s^+ \phi$ is of order $10^{-7}$ which may be measured in the near future by KEK and SLAC $B$ factories. The small branching ratio predicted in standard model makes this channel sensitive to new physics contributions., Comment: 13 pages, including 1 figure, revtex4

We calculate the branching ratios and $\mathrm{CP}$ asymmetries for ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}, {B}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{0},$ and ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ decays, in a perturbative QCD approach. In this approach, we calculate nonfactorizable and annihilation type contributions, in addition to the usual factorizable contributions. We find that the annihilation diagram contributions are not very small as previously argued. Our result is in agreement with the measured branching ratio of $\stackrel{\ensuremath{\rightarrow}}{B}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ by the CLEO Collaboration. With a non-negligible contribution from annihilation diagrams and a large strong phase, we predict a large direct $\mathrm{CP}$ asymmetry in ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}},$ and ${\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0},$ which can be tested by the current running B factories.

We review the current status of theoretical study of non-leptonic two body B decays. There are two independent directions for this purpose. One is the so called QCD factorization approach (or BBNS approach), which is based on naive factorization approach. The other one is named perturbative QCD approach. We list the different ideas and applications of the two method, and make a comparison between the two., Comment: 12 pages, including 2 figures, invited talk given at International Conference on Flavor Physics (ICFP 2001), Zhang-Jia-Jie City, Hunan, China, 31 May - 6 Jun 2001

Using the generalized factorization approach, we calculate the CP asymmetries of charmless B decays. A number of decay channels has large CP asymmetries, which can be measured in the B factories., Comment: 8 pages, LaTex, 1 figure, Invited Talk given at the 3rd International Conference on B Physics and CP Violation, Taipei, Dec. 3 - 7, 1999, to appear in the proceedings

We re-analyse the long distance contributions to the process $b \to s l^+ l^-$. Full $q^2$-behavior of the vector meson dominance amplitude is used together with the effect of Terasaki suppression, and comparisons with the previous results are given. We show that the interference between short- and long- distance contributions makes it difficult to extract the short distance information from the dominant long distance background, either in the dilepton invariant mass distribution or in the single lepton energy spectrum., Latex file, 10 pages, 2 figures included