Search

Baryonic two-body $B$ mesons decays have been measured experimentally for some time, which provides an excellent ground for studying the QCD of baryonic $B$ decays. In this work, we investigate the two-body doubly-charmed baryonic $B$ decays in the perturbative QCD (PQCD) approach including higher twist contributions to the light-cone distribution amplitudes (LCDAs). The charmed baryon LCDAs are included up to the twist four and the effect of the subleading component of the $B$ meson LCDAs is studied for details. With the inclusion of these higher-power contributions, the PQCD results on rates can explain the current experimental data well. Moreover, we note that the SU(3) symmetry breaking is important in the concerned processes and play an essential role in understanding the measurements of $\mathcal{B}(\overline{B}^0\to \Lambda_c^+\overline \Lambda_c^-)$ and $ \mathcal{B}({B}^-\to\Xi_c^0\overline \Lambda_c^-)$. We also evaluate the angular asymmetries for the first time, which have neither been measured experimentally nor calculated theoretically. All these predictions can be tested in future., Comment: 19 pages, 2 figures, 9 tables, Matches published version in JHEP

Based on the fitting results of the LHCb collaboration on the contributions of various intermediate resonances to the $B^{+}\to\pi^{+}\pi^{+}\pi^{-}$ decay, we make systematically calculate the branching fractions and localized $CP$ asymmetries of the quasi-two-body $B^{+}\to \pi^{+} \left( \rho(770), \omega(782), \rho(1450), f_{2}\left(1270\right)\to\right)\pi^{+}\pi^{-}$ decays within the perturbative QCD (PQCD) approach. Our theoretical predictions for the branching fractions agree well with the data within the errors. In order to further test the framework of the three-body $B$ decays in PQCD and the wave functions of $\pi\pi$ pair, we also calculate the branching fractions of the corresponding two-body $B^{+}\to\pi^{+}\rho(770)$, $B^{+}\to\pi^{+}\omega(782)$ and $B^{+}\to\pi^{+}f_{2}\left(1270\right)$ decays under the narrow-width-approximation, which are in consistence with the experimental data. The direct $CP$ asymmetries of $B^{+}\to\pi^{+}(\rho(770/1450)\to) \pi^{+}\pi^{-}$ decays are found to be very small because these decay modes are tree-dominated. However, due to the large penguin contributions from the chiral enhanced annihilation diagrams, $B^{+}\to\pi^{+} (f_{2}\left(1270\right)\to )\pi^{+}\pi^{-}$ decay has a large direct $CP$ asymmetry, which is also discovered by LHCb collaboration. A relatively large $CP$ asymmetry is also expected in the $B^+\to\pi^+ (\omega\to)\pi^+\pi^-$ decay occurring via $\rho-\omega$ mixing, which would be measured LHCb and Belle-II experiments in future., Comment: 17 pages, 5 figure

Within QCD factorization approach, we employ the new results of form factors of $B_s \to \phi$ and calculate the branching fractions, CP asymmetries (CPAs) and polarization fractions of the decay modes $B_s \to \phi (\rho^0, \omega)$ in both the standard model (SM) and the family non-universal $Z^\prime$ model. We find that in SM the above observables are relate to two parameters $\rho_H$ and $\phi_H$, which characterize the end-point divergence in the hard spectator-scattering amplitudes. When setting $\rho_H=0.5$ and $\phi_H\in [-180,180]^\circ$, the theoretical uncertainties are large. By combining the experimental data, our results can be used to constrain these two parameters. Supposing $\rho_H=0$, we study the effects of $Z^\prime$ boson on the concerned observables. With the available branching fraction of $B_s \to \phi \rho^0$, the possible ranges of parameter spaces are obtained. Within the allowed parameter spaces, the branching fraction of $B_s \to \phi \omega$ can be enlarged remarkably. Furthermore, the new introduced weak phase plays important roles in significantly affecting the CPAs and polarization fractions, which are important observables for probing the effects of NP. If these decay modes were measured in the on-going LHC-b and Belle-II experiments in future, the peculiar deviation from SM could provide a signal of the family non-universal $Z^\prime$ model, which can also be used to constrain the mass of $Z^\prime$ boson in turn., Comment: 9 pages, 5 figures

The scalars $f_0$ closest to 1.5 GeV contain the mesons $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, and the latter two ones are usually viewed as the potential candidates for the scalar glueballs. In this work, by including the important contributions from the vertex corrections, we study the decays $B^0 \to J/\psi f_0$ within the improved perturbative QCD approach and analyze the possible scalar glueball hunting. Together with the two mixing models, namely, $f_0(1500) (f_0(1710))$ being the primary scalar glueball in model I (II), and two classification scenarios, namely, $f_0$ being the $q\bar q$ excited (ground) states in scenario 1 (2), the branching fractions associated with their ratios for $B^0 \to J/\psi f_0$ are evaluated comprehensively. The predictions with still large uncertainties in the considered two mixing models are roughly consistent with currently limited data, which indicates that both more rich data and more precise predictions are urgently demanded to figure out the scalar glueball clearly in the future. Moreover, several interesting ratios between the branching fractions of $B^0 \to J/\psi f_0(\to \pi^+ \pi^-/K^+ K^-)$ and $B^0 \to J/\psi \rho^0/\phi (\to \pi^+ \pi^-/ K^+ K^-)$ that could help us to understand the nature of scalar $f_0$ are defined and predicted theoretically. These ratios should be examined in future experiments., Comment: 28 pages, 3 figures, 6 tables; revised version according to referee's comments; contents improved and references added

Motivated by recent advances in experimental measurements of heavy baryon decays, the charmonium decays of single $b$-baryon are investigated systematically in the framework of perturbative QCD approach. We calculate the decay branching ratios and helicity amplitudes as well as many pertinent decay asymmetry parameters that characterize the angular decay distributions. In particular, we estimate the fragmentation fractions of $b$ quark to $b$-baryons based on the current world averages of the branching ratio multiplied by fragmentation fraction. Some of the featured results are compared with the predictions of other approaches and experimental data. We also evaluate the branching ratios and angular asymmetries of the $\Sigma_b$ and $\Xi'_b$ decay modes, which have neither been measured experimentally nor calculated theoretically. Our results could be helpful for a future experimental search for them and provide deeper insights in the understanding of the dynamics of heavy-flavor weak decay processes., Comment: 30 pages,3 figures, 10 Tables;matches version published in PRD

LHCb Collaboration studied the resonant structure of $B_s\to \overline{D}^0K^-\pi^+$ decays using the Dalitz plot analysis technique, based on a data sample corresponding to an integrated luminosity of $3.0{\rm fb}^{-1}$ of $pp$ collision. The $K^-\pi^+$ components have been analyzed in the amplitude model, where the decay amplitude is modeled to be the resonant contributions with respect to the intermediate resonances $K^*(892)$, $K_0^*(1430)$ and $K_2^*(1430)$. Motivated by the experimental results, we investigate the color-favored quasi-two-body $B \to \overline{D}^0K\pi$ decays in the framework of the perturbative QCD (PQCD) approach. We calculate the the branching fractions by introducing the appropriate wave functions of $K\pi$ pair. Our results are in agreement well the available data, and others can be tested in LHCb and Belle-II experiments. Using the narrow-width-approximation, we also extract the branching fractions of the corresponding two-body $B\to \overline D R$ decays, which agree to the previous theoretical calculations and the experimental data within the errors. There are no $CP$ asymmetries in these decays in the standard model, because these decays are all governed by only the tree operators., Comment: 18 pages, 1 figures

The nonleptonic decays $B_{d,s} \to K^{*0} {\overline K^{*0}}$ are reanalyzed in perturbative QCD approach, which is based on the $k_{\rm T}$ factorization. In the standard model, the calculated branching fraction and longitudinal polarization fraction of $B_{d} \to K^{*0} {\overline K^{*0}}$ are in agreement with experimental measurements, while the predictions of $B_{s} \to K^{*0} {\overline K^{*0}}$ cannot agree with data simultaneously. The parameter that combines of longitudinal polarization fractions and branching fractions evaluated to be $L_{K^*\overline{K}^{*0}}^{\rm PQCD}= 12.7^{+5.6} _{-3.2}$, which is also larger than that abstracted from experimental measurements. We then study all observables by introducing a family non-universal $Z^{\prime}$ boson in $b\to s q\bar q$ transitions. In order to reduce the number of new parameters, we simplify the model as possible. It is found that with the fixed value $\omega_{B_s}=0.55$, these exists parameter space where all measurements, including the branching fraction, longitudinal polarization fraction and $L_{K^*\overline{K}^{*0}}$-parameter, could be accommodated simultaneously. All our results and the small parameter space could be further tested in the running LHC experiments, Belle-II and future high-energy colliders., Comment: 21 pages, 6 figures

The axial-vector mesons $f_1(1285)$ and $f_1(1420)$ are particularly viewed as the mixtures of flavor states $f_n$ and $f_s$ with mixing angle $\varphi$. In order to determine this angle, we study the $B_{d,s}^0\to J/\psi f_1(1285,1420)$ and $B_{d,s}^0\to \eta_c f_1(1285,1420)$ decays in perturbative QCD (PQCD) approach, including the effects of vertex corrections, nonfactorizable diagrams and penguin operators. Not only the branching fractions, but also the direct $CP$ asymmetries and the polarization fractions are calculated. It is found that the branching fractions of these decays are large enough to be measured in the running LHCb and Belle-II experiments. Moreover, in comparison with the observed ${\cal B}(B_{d,s}^0 \to J/\psi f_1(1285))$, $B_s^0 \to (J/\psi, \eta_c) f_1(1420)$ decays have large branching fractions, which could be measured promisingly through $f_1(1420) \to K_S^0 K^\pm \pi^\mp$ in experiments. We also propose several ratios that could be used to further constrain the absolute value of the mixing angle $\varphi$, but its sign cannot be determined yet in these decays. The direct CP asymmetries of these decays indicate the penguin pollution in the $B_d^0 \to (J/\psi, \eta_c) f_1$ decays cannot be neglected. We acknowledge that there are large theoretical uncertainties arising from the distribution amplitudes of axial-vector mesons and charmonium states, and more precise nonperturbative parameters are called. The comparisons between our results and future experimental data would help us to understand the nature of $f_1$ states and to test the PQCD approach., Comment: 18 pages, 3 figures, journal version, published in EPJC

Three-body $B$ decays not only significantly broaden the study of $B$ meson decay mechanisms, but also provide information of resonant particles. Because of complicate dynamics, it is very hard for us to study the whole phase space in a specific approach. In this review, we take $B\to K({\cal R}\to) K^+K^-$ decays as examples and show the application of the perturbative QCD (PQCD) approach in studying the quasi-two-body $B$ decays, where two particles move collinearly with large energy and the bachelor one recoils back. To describe the dynamics of two collinear particles, the ($S$, $P$ and $D$)-wave functions of kaon-pair with different waves are introduced. By keeping the transverse momenta, all possible diagrams including the hard spectator diagrams and annihilation ones can be calculated in PQCD approach. Most results are well consistent with the current measurements from BaBar, Belle and LHCb experiments. Moreover, under the narrow-width approximation we can extract the branching fractions of the two-body decays involving the resonant states, and also predict the branching fractions of the corresponding quasi-two-body decays $B\to K(\cal{R}\to )\pi^+\pi^-$. All prediction are expected to be tested in the ongoing LHCb and Belle-II experiments., Comment: 12 pages,4 figures, invited mini-review for the special issue "Heavy Flavor Physics and CP Violation" of Advances in High Energy Physics

In this work, we investigate the $B_s\to V S$ decays in the perturbative QCD approach, where $V$ and $S$ denote the vector meson and scalar meson respectively. Based on the two-quark structure, considering two different scenarios for describing the scalar mesons, we calculate the branching fractions and the direct $CP$ asymmetries of all $B_s\to VS$ decays. Most branching fractions are predicted to be at $10^{-7}$ to $10^{-5}$, which could be measured in the LHCb and Belle-II experiments, especially for these color-allowed $B_s\to \kappa(800)(K_0^*(1430))K^*$ decays. It is found that the branching fractions of $B_s\to K_0^{*0}(1430)\bar{K}^{*0}$ and $B_s\to K_0^{*+}(1430)\bar{K}^{*-}$ are very sensitive to the scenarios, which can be used to determine whether $K_0^{*0}(1430)$ belongs to the ground state or the first excited state, if the data were available. We also note that some decays have large direct $CP$ asymmetries, some of which are also sensitive to the scenarios, such as the $B_s \to a_0^+(1450)K^{*-}$ and the $B_s\to f_0(1500) K^{*0}$ decays. Since the experimental measurements of $B_s\to VS$ decays are on the way, combined with the available data in the future, we expect the theoretical predictions will shed light on the structure of the scalar mesons., Comment: 18 Pages, 3 Figures

Using the perturbative QCD approach, we studied the effects from hadronic structure of photon on the pure annihilation rediative decays $B\to\phi\gamma$ and $B_s\to(\rho^0,\omega)\gamma$. These decays have small branching fractions due to the power suppression by the $\Lambda/m_B$, which make them very sensitive to the next-leading power corrections. The quark components and the related two-particle distribution amplitudes of a final state photon are introduced. The branching fractions can be enhanced remarkably by the factorizable and nonfactorizable emission diagrams. The branching fraction of $B\to \phi\gamma$ even increases by about 40 times, and those of $B_s \to \rho^0\gamma$ and $B_s \to \omega\gamma$ are at the order of ${\cal O}(10^{-10})$. We also note that the ratio of branching fractions of $B_s \to \rho^0\gamma$ and $B_s \to \omega\gamma$ is very sensitive to the effects from hadronic structure of photon. All above results could be tested in future., Comment: 9 pages, 1 figure, to be published in Chinese Physics C

Motivated by the measurements of branching fractions of the quasi-two-body decays $B^0\to K^{*0}(f_0(980)\to )\pi^+\pi^-$ and $B^0\to \rho^0(f_0(980)\to )\pi^+\pi^-$, we study the charmless $B\to V (f_0(980)\to ) \pi^+\pi^-$ decays in the perturbative QCD approach. Supposing that $f_0(980)$ is a two-quark state and mixture of $n\bar n=(u\bar u+d\bar d)/\sqrt 2$ and $s\bar s$ with the mixing angle $\theta$, we calculate the branching fractions of these decays with the new introduced $s$-wave $\pi^+\pi^-$-pair wave function. When the mixing angle $\theta$ lies in the range $[135^{\circ}, 155^{\circ}]$, the calculated branching fractions of the $B^0\to K^{*0}f_0(980)\to K^{*0}\pi^+\pi^-$ and $B^0\to \rho^0f_0(980)\to \rho^0\pi^+\pi^-$ decays are in agreement with the experimental data. The branching fractions of other decays could be measured in the current LHCb and Belle II experiments. Considering the isospin symmetry, we also estimate the branching fractions of the quasi-two-body decays $B\to Vf_0(980)\to V\pi^0\pi^0$, which are half of those the corresponding decays $B\to Vf_0(980)\to V\pi^+\pi^-$. Moreover, the direct $CP$ asymmetries of these decays are also calculated, and some of them can be tested in the current experiments., Comment: 10 pages, 2 figures

In 2017, LHCb collaboration reported their first observation of the rare decays $B_s \to \phi (f_0(980)$ $/f_2(1270) \to ) \pi^+\pi^-$ and the evidence of $B^0 \to \phi(f_0(980)/f_2(1270)\to)\pi^+\pi^-$. Motivated by this, we study these quasi-two-body decays in the perturbative QCD approach. The branching fractions, $CP$ asymmetries and the polarization fractions are calculated. We find that within the appropriate two-meson wave functions, the calculated branching fractions are in agreement with the measurements of LHCb. Based on the narrow-width approximation, We also calculate the branching fractions of the quasi-two-body $B_{d,s}\to \phi(f_0(980)/f_2(1270)\to) \pi^0\pi^0$ and $B_{d,s}\to \phi(f_2(1270)\to) K^+K^-$, and hope the predictions to be tested in the ongoing LHCb and Belle II experiments. Moreover, the processes $B_{d,s}\to \phi f_2(1270)$ are also analyzed under this approximation. We note that the $CP$ asymmetries of these decays are very small, because these decays are either penguin dominant or pure penguin processes., Comment: 21 Pages, 1 figure

Recent anomalies in decays induced by $b\to c \ell^- \bar\nu_\ell$ transitions raise the question about such phenomena in the $D$ decays induced by $c\to (s,d)\ell^+\nu_\ell$ transitions. In the experimental side, current measurements on the pure leptonic and semileptonic $D$ decays agree with the standard model predictions, such agreements can be used to constrain the new physics (NP) contributions. In this work, we extend the standard model by assuming general effective Hamiltonians describing the $c\to (s,d)\ell^+\nu_\ell$ transitions including the full set of the four-fermion operators. Within the latest experimental data, we perform a minimum $\chi^2$ fit of the Wilson coefficient corresponding to each operator. The results show that the Wilson coefficients of scalar operators in muon sector are at the order of ${\cal O}(10^{-2})$, and others are at the order of ${\cal O}(10^{-3})$. The lepton flavor universality could be violated by the scalar operators. We also calculate the branching fractions, the forward-backward asymmetries and polarizations of final vector mesons and leptons with the fitted Wilson coefficients of scalar and tensor operators. It is found that the pure leptonic decays are very sensitive to the scalar operators. The effects of NP on the semileptonic decays with electron are negligible, while for the semileptonic decays with muon the effects of scalar operators will show up in the forward-backward asymmetries and polarizations of muon of $D \to P\mu^+ \nu_\mu$. The future measurements in BESIII and Belle II experiments will help us to test effects of NP and to further test new physics models., Comment: 28 Pages,9 figures

We investigate the $B_{d,s}^0 \to f_1 f_1$ decays in the framework of perturbative QCD(PQCD) approach with a referenced value $\phi_{f_1} \sim 24^\circ$. Here, $f_1$ denotes the axial-vector mesons $f_1(1285)$ and $f_1(1420)$ with mixing angle $\phi_{f_1}$ in the quark-flavor basis. The observables such as branching ratios, direct CP violations, and polarization fractions of the $B_s^0 \to f_1 f_1$ decays are predicted for the first time. We find that: (i) the almost pure penguin modes $B_s^0 \to f_1 f_1$ have large branching ratios in the order of $10^{-6} \sim 10^{-5}$ due to the Cabibbo-Kobayashi-Maskawa enhancement and generally constructive interferences between the amplitudes of $B_s^0 \to f_n f_s$ and $B_s^0 \to f_s f_s$ with $f_n$ and $f_s$ being the quark-flavor states of $f_1$ mesons; (ii) The observables receive important contributions from the weak annihilation diagrams in the PQCD approach. In particular, without the annihilation contributions, the $B_s^0 \to f_1(1420) f_1(1420)$ branching ratio will decrease about 81% and its longitudinal polarization fraction will reduce around 43%. And (iii) the dependence of the $B_{d,s}^0 \to f_1 f_1$ decay rates on $\phi_{f_1}$ exhibits some interesting line shapes, whose confirmations would be helpful to constrain the determination of $\phi_{f_1}$ inversely. All the PQCD predictions await for the (near) future examinations at Large Hadron Collider beauty and/or Belle-II experiments to further understand the properties of the axial-vector mesons and the perturbative dynamics released from the considered decay modes., Comment: 19 pages, 3 figures, and 6 tables. the values in (A12) corrected, the numerical results and conclusions remain unchanged

We suggest that the uncertain state $f_X(1500)$ observed by Belle and BaBar more than a decade ago, which has been viewed as a single scalar or a combination of several even spin resonances, is the vector $\rho^0(1450)$ reported recently by LHCb. Adopting the perturbative QCD approach, we determine the di-kaon distribution amplitudes with the $\rho^0(1450)$ resonance from the LHCb data for the quasi-two-body decays $B^{\pm}\to \pi^{\pm}\rho^0(1450)\to\pi^{\pm}K^+K^-$. It is then shown that the $B^+ \to K^+K^+K^-$ decay spectrum around the invariant mass $M(K^+K^-)\sim 1.5~\rm GeV$ measured by BaBar can be well described by the resonant contribution from $\rho^0(1450)$. The broad structure in the $B^{+}\to K^{+} K_SK_S$ spectrum around the invariant mass $1.5~\rm GeV$ of a $K_SK_S$ pair, which $\rho^0(1450)$ cannot decay into because of Bose-Einstein statistics, can be accounted for by a nonresonant $S$-wave contribution alone. The branching fractions and/or the direct $CP$ asymmetries of the $B^{\pm}\to \pi^{\pm}\rho^0(1450)\to\pi^{\pm}K^+K^-$, $B^{+}\to K^{+}\rho^0(1450)\to K^+K^+K^-$ and $B^{0}\to K^{0}\rho^0(1450)\to K^0K^+K^-$ modes are predicted, which can be tested at the ongoing LHCb and Belle-II experiments. We encourage experimental colleagues to scrutinize our postulation by analyzing relevant data with higher precision., Comment: 7 Pages, 3 Figures. Accepted by PRD

Motivated by the first untagged decay-time-integrated amplitude analysis of $B_s \to K_SK^{\mp}\pi^{\pm}$ decays performed by LHCb collaboration, where the decay amplitudes are modeled to contain the resonant contributions from intermediate resonances $K^*(892)$, $K_0^*(1430)$ and $K_2^*(1430)$, we comprehensively investigate the quasi-two-body $B_{s} \to K^0/\overline{\kern -0.2em K}^0 K^{\pm}\pi^{\mp}$ decays, and calculate the branching fractions and the time-dependent $CP$ asymmetries within the perturbative QCD approach based on the $k_T$ factorization. In the quasi-two-body space region the calculated branching fractions with the considered intermediate resonances are in good agreement with the experimental results of LHCb by adopting proper $K\pi$ pair wave function, describing the interaction between the kaon and pion in the $K\pi$ pair. Furthermore,within the obtained branching fractions of the quasi-two-body decays, we also calculate the branching fractions of corresponding two-body decays, and the results consist with the LHCb measurements and the earlier studies with errors. For these considered decays, since the final states are not flavour-specific, the time-dependent $CP$ could be measured. We calculate six $CP$-violation observables, which can be tested in the ongoing LHCb experiment., Comment: 20 pages

In this work, we study the ($S$, $P$ and $D$)-wave $K^+K^-$ contributions to $B\to KKK$ decays in the perturbative QCD approach at leading order. Within the two-meson wave functions describing the nonperturbative dynamics in the kaon-pair for different waves, we calculate the branching fractions and the direct $CP$ asymmetries of these decay modes in the corresponding resonance regions. Most of our numerical results are well consistent with the current measurements. We note that the narrow-width approximation is invalid in the quasi-two-body decays $B\to Kf_0(980)\to KKK$. For other decays, under the narrow-width approximation we can extract the branching fractions of the corresponding two-body decays involving the intermediate resonant states, and the related branching fractions agree with the current experimental data well. Furthermore, we also predict the corresponding quasi-two-body decays $B\to K\pi^+\pi^-$, which are expected to be measured in the ongoing LHCb and Belle-II experiments., Comment: 28 Pages, and 3 figures

Motivated by the observations of the decays $B^0 \to K_0^{*}(1430)^0 f_0(980)$ and $ B^0 \to K_2^{*}(1430)^0 f_0(980)$ from BaBar collaboration, we study the $B^{0(+)} \to K_{0,2}^{*}(1430)^{0(+)} f_0(980)/\sigma$ decays in the perturbative QCD approach for the first time. In the absence of reliable nonperturbative wave functions we only assume the scalar meson $f_0(980)$ and $\sigma$ are two-quark ground states. In our calculations, these decays are all dominated by the hard-scattering emission and annihilation diagrams, while the factorizable emission diagrams are forbidden or suppressed heavily by the vector decay constants. Furthermore, the branching fractions are sensitive to the mixing between $f_0(980)$ and $\sigma$. Comparing our results with the experimental data, a large mixing angle $\theta$ is favored. Taking $\theta=145^\circ$, the orders of branching fractions of $B \to K_0^{*}(1430)^0 \sigma$, $B \to K_{2}^{*}(1430)^0 \sigma$ and $B \to K_{0,2}^{*}(1430)^0 f_0(980)$ are predicted to be $10^{-4}$, $10^{-5}$ and $10^{-6}$, respectively, which can be measured in the current experiments such as LHCb and Belle-2. In addition, although these decays are penguin dominant, the mixing also leads to large direct $CP$ asymmetries in these decays. With the precise data in future, our results could shed light on the inner structure of the scalar mesons and can be used to determine the mixing angle of the $\sigma-f_0(980)$ system., Comment: 21 pages, 5 figures

Recent experimental results of ${\cal R}(D^{(*)})$ deviate from the standard model (SM) by $3.1\sigma$, suggesting a new physics (NP) that affects the $b\to c \tau \bar\nu_\tau$ transition. Motivated by this, we investigate the possible NP effects in the $\Lambda_b\to\Lambda_c \tau\bar\nu_\tau$ decay. For this purpose, assuming the neutrinos are left-handed, we calculate in detail the helicity amplitudes of $\Lambda_b\to\Lambda_c \ell\bar\nu_\ell$ decays with all possible four-fermion operators. Within the latest results of $\Lambda_b\to\Lambda_c$ form factors from lattice QCD calculations, we study these decays in a model-independent manner. The differential and total branching fractions and other observables are calculated. In SM, we obtain the ratio ${\cal R}(\Lambda_c)=0.33\pm0.01$. Supposing that NP only affects the third generation fermions, we present the correlations among ${\cal R}(D)$, ${\cal R}(D^*)$ and ${\cal R}(\Lambda_c)$. We perform a minimum $\chi^2$ fit of the wilson coefficient of each operator to the latest experimental data of different observables. It is found that the left-handed scalar operator ${\cal O}_{SL}$ affects the branching fraction remarkably, and the ratio ${\cal R}(\Lambda_c)$ can be enhanced by $30\%$. For other operators, the ratio amounts to $0.38\pm0.02$, which is larger than prediction of SM by $20\%$. Using the fitted values of the wilson coefficients of the single NP operators, we also give a prognosis for the physical observables of $\Lambda_b\to\Lambda_c \tau\bar\nu_\tau$. Furthermore, we also study the effects of three typical NP models on $\Lambda_b\to\Lambda_c \tau\bar\nu_\tau$. We hope our results can be tested in the current LHCb experiment and the future high energy experiments., Comment: 24 pages,8 figures

Encouraged by the global agreement between theoretical predictions and experimental measurements for $B \to J/\psi V$ decays, we extend that perturbative QCD formalism to $B_{d,s}^0 \to J/\psi f_0(500) [f_0(980)]$ decays at the presently known next-to-leading order in the quark-antiquark description of $f_0(500)$ and $f_0(980)$. With the angle $\phi_f \approx 25^\circ$ of the $f_0(500)-f_0(980)$ mixing in the quark-flavor basis, we find that the branching ratios of the $B_d^0 \to J/\psi f_0(500) (\to \pi^+ \pi^-)$ and $B_{d,s}^0 \to J/\psi f_0(980) (\to \pi^+ \pi^-)$ modes generally agree with the current data or the upper limits within uncertainties, except for the seemingly challenging $B_s^0 \to J/\psi f_0(500) (\to \pi^+\pi^-)$ one. Then, we further explore the relevant observables of the $B_{d,s}^0 \to J/\psi f_0(500) [f_0(980)]$ decays, which could provide further constraints on the mixing angle $\phi_f$ and/or SU(3) flavor symmetry breaking effects. As a byproduct, we predict ${\rm BR}(B_{d}^0 \to J/\psi f_0(980)(\to K^+ K^-))=5.8^{+3.1}_{-2.9} \times 10^{-7}$ and ${\rm BR}(B_{s}^0 \to J/\psi f_0(980)(\to K^+ K^-)) =4.6^{+2.6}_{-2.3} \times 10^{-5}$. All theoretical predictions await the future examinations with high precision., Comment: RevTex file, 15 pages, 5 figures; final version to appear in PRD

In this paper we calculate the power corrections to the pion transition form factor within the framework of perturbative QCD approach on the basis of $k_T$ factorization. The power suppressed contributions from higher twist pion wave functions and the hadronic structure of photon are investigated. We find that there exists strong cancellation between the two kinds contributions, thus the total power corrections considered currently are very small, and the prediction of the leading power contribution with joint resummation improved perturbative QCD approach is almost unchanged. This result confirms that the pion transition form factor is a good platform to constrain the nonperturbative parameters in pion wave functions. Moreover, our result can accommodate the anomalous data from BaBar, or agrees with results from Belle according to the choice of Gegebauer moment in the pion wave function, and the more precise experimental data from Belle-II is expected., Comment: 5 figures, 1 table

The leptonic radiative decay $B \to \gamma l\nu$ is of great importance in the determination of $B$ meson wave functions, and evaluating the form factors $ F_{V,A}$ are the essential problem on the study of this channel. We computed next-to-leading power corrections to the form factors within the framework of PQCD approach, including the power suppressed hard kernel, the contribution from a complete set of three-particle $B$ meson wave functions up to twist-4 and two-particle off light-cone wave functions, the $1/m_b$ corrections in heavy quark effective theory, and the contribution from hadronic structure of photon. In spite of large theoretical uncertainties, the overall power suppressed contributions decreases about $50\%$ of the leading power result. The $\lambda_B$ dependence of the integrated branching ratio is reduced after including the subleading power contributions, thus the power corrections lead to more ambiguity in the determination of $\lambda_B$ from $B \to \gamma l\nu$ decay., Comment: 7 figures and 1 table

Within the framework of perturbative QCD approach based on $k_T$ factorization, we studied 40 $B_c \to DS$ decay modes in the leading order and leading power, where "S" stands for the light scalar meson. Under two different scenarios (S1 and S2) for the description of scalar mesons, we explored the branching fractions and related CP asymmetries. As a heavy meson consisting of two heavy quarks with different flavor, the light-cone distribution amplitude of $B_c$ meson has not been well defined, so the $\delta$-function is adopted. The contributions of emission diagrams are suppressed by the vector decay constants and CKM elements, the contributions of annihilation are dominant. After the calculation, we found some branching fractions are in the range of $[10^{-5}, 10^{-4}]$, which could be measured in the current LHCb experiment, and other decays with smaller branching fractions will be tested at the high-energy colliders in future. Furthermore, some decay modes have large CP asymmetries, but they are unmeasurable currently due to the small branching fractions., Comment: 29 pages. arXiv admin note: text overlap with arXiv:0811.2648 by other authors

Within the perturbative QCD approach, we investigated the Cabibbo-Kobayashi-Maskawa-favored $B \to \overline{D} S$ ("$S$" denoting the scalar meson) decays on the basis of the two-quark picture. Supposing the scalar mesons are the ground states or the first excited states, we calculated the the branching ratios of 72 decay modes. Most of the branching ratios are in the range $10^{-4}$ to $10^{-7}$, which can be tested in the ongoing LHCb experiment and the forthcoming Belle-II experiment. Some decays, such as $B^+ \to \overline{D}^{(*)0} a_0^+(980/1450)$ and $B^+ \to D^{(*)-} a_0^+(980/1450)$, could be used to probe the inner structure and the character of the scalar mesons, if the experiments are available. In addition, the ratios between the $Br(B^0\to \overline{D}^{(*)0}\sigma)$ and $Br(B^0\to \overline{D}^{(*)0}f_0(980))$ provide a potential way to determine the mixing angle between $\sigma$ and $f_0(980)$. Moreover, since in the standard model these decays occur only through tree operators and have no $CP$ asymmetries, any deviation will be signal of the new physics beyond the standard model., Comment: 2 figures, 6 tables

Two-body charmless hadronic $B_c$ decays involving a light $1^3\!P_2$-tensor($T$) meson are investigated for the first time within the framework of perturbative QCD(pQCD) at leading order, in which the other meson is the lightest pseudoscalar($P$) or vector($V$) state. The concerned processes can only occur through the pure weak annihilation topology in the standard model. We predict the CP-averaged branching ratios and polarization fractions of those considered decays in Cabibbo-Kobayashi-Maskawa(CKM) favored and suppressed modes. Phenomenologically, several modes$-$such as the $B_c \to K_2^*(1430) K$ and the CKM-favored $B_c \to TV-$have large decay rates of $10^{-6}$, which are expected to be detected at Large Hadron Collider experiments in the near future. Moreover, all of the $B_c \to TV$ modes are governed by the longitudinal amplitudes in the pQCD calculations and the corresponding fractions vary around $78\%$-$98\%$. A confirmation of these results could prove the reliability of the pQCD approach used here and further shed some light on the annihilation decay mechanism., Comment: 10 pages, 1 figure, 4 tables, RevTex file; Acknowledgment updated with a grant number, Matching the published version

Doubly-heavy baryons, with two heavy and one light quarks, are expected to exist in QCD and their masses have been predicted in the quark model. However their existence is not well established so far in experiment. In this work, we explore the possibility of searching for $\Xi_{bc}$ and $\Xi_{cc}^{+}$ in the $W$-exchange processes, $\Xi_{bc}^{0}\to pK^{-}$ and $\Xi_{cc}^{+}\to \Sigma_{c}^{++}(2520)K^{-}$. On the basis of perturbative calculations, we estimate the branching ratio of the first decay as ${\cal BR}(\Xi_{bc}^0\to p^+ K^-)\approx3.21\times {\cal R}^2_f \times {\cal R}_{\tau}\times 10^{-7}$, where ${\cal R}_f$ (${\cal R}_{\tau}$) are the ratios of the decay constants (lifetimes) of $\Xi_{bc}^{0}$ and $\Lambda_b^{0}$. The branching ratio of $\Xi_{cc}^{+}\to \Sigma_{c}^{++}(2520)K^{-}$ is related to that of $\Lambda_c^+\to \Delta^{++} K^-$, and thereby a conjectured topology analysis leads to the range for the branching ratio as: ${\cal BR}(\Xi_{cc}^+\to \Sigma_{c}^{++}(2520) K^-)\in \left[0.36\%,1.80\%\right]$. The decay $\Xi_{cc}^+\to \Sigma_{c}^{++}(2520) K^-$ would be reconstructed in the $ \Lambda_{c}^{+}K^{-}\pi^{+}$ final state which is easy to access even at a hadron collider. Based on the two facts that abundant heavy quarks can be produced at a hadron collider like LHC, and the branching ratios of $\Xi_{bc}^{0}\to pK^{-}$ and $\Xi_{cc}^{+}\to \Sigma_{c}^{++}(2520)K^{-}$ are sizable, we urge our experimental colleagues to perform a search at LHCb. This will presumably lead to the discovery of the $\Xi_{bc}$ and $\Xi_{cc}^{+}$ , and precision measurements of the branching ratios in the future are helpful to investigate their decay mechanism., Comment: 10 pages; 2 figures; version published on Physics Letters B

Based on the assumption of two-quark structure for the light scalar mesons, within the framework of perturbative QCD approach, we investigate the $B_{q}\to D_{(s)}^{(*)} S(q=u,d,s)$ decays induced by $b\to u $ transition, where $S$ denotes a light scalar meson. Under two different scenarios, we calculate the branching ratios of 96 decay modes totally, which are in the range of $10^{-5}$ to $10^{-8}$. The comparison between our predictions and the experimental data will allow us to probe the inner structure of the scalar mesons. In the standard model, since all decays can only occur through tree operators, there are no $CP$ asymmetries. From our calculations, it has been shown that the annihilation type diagrams, especially the nonfactorizable annihilation diagrams, play important roles in the decay amplitudes, especially for these color-suppressed and pure annihilation type decay modes. We also find that the branching ratios of color-allowed type decays are sensitive to the different scenarios, so the measurements of them will be ideal places to differentiate the different scenarios. It can be found that the ratios between $Br(B^0\to D^{(*)0}\sigma)$ and $Br(B^0\to D^{(*)0}f_0)$, and between $Br(B^+\to D^{(*)+}\sigma)$ and $Br(B^{+}\to D^{(*)+}f_0)$ can be used to determine the mixing angle of $\sigma$ and $f_0$.

We investigate the branching ratios, the polarization fractions, the direct CP-violating asymmetries, and the relative phases in 20 nonleptonic decay modes of $B \to f_1 V$ within the framework of perturbative QCD approach at leading order with $f_1$ including two $^3\!P_1$-axial-vector states $f_1(1285)$ and $f_1(1420)$. Here, $B$ denotes $B^+$, $B^0$, and $B_s^0$ mesons and $V$ stands for the lightest vector mesons $\rho$, $K^*$, $\omega$, and $\phi$ , respectively. The $B_s^0 \to f_1 V$ decays are studied theoretically for the first time in the literature. Together with the angle $\phi_{f_1} \approx (24^{+3.2}_{-2.7})^\circ$ extracted from the measurement through $B_{d/s} \to J/\psi f_1(1285)$ modes for the $f_1(1285)-f_1(1420)$ mixing system, it is of great interest to find phenomenologically some modes such as the tree-dominated $B^+ \to f_1 \rho^+$ and the penguin-dominated $B^{+,0} \to f_1 K^{*+,0}, B_s^0 \to f_1 \phi$ with large branching ratios around ${\cal O}(10^{-6})$ or even ${\cal O}(10^{-5})$, which are expected measurable at the LHCb and/or the Belle-II experiments in the near future. The good agreement [sharp contrast] of branching ratios and decay pattern for $B^+ \to f_1 \rho^+, B^{+,0} \to f_1(1285) K^{*+,0} [B^{+,0} \to f_1(1420) K^{*+,0}]$ decays between QCD factorization and perturbative QCD factorization predictions can help us to distinguish these two rather different factorization approaches via precision measurements, which would also be helpful for us to explore the annihilation decay mechanism through its important roles for the considered $B \to f_1 V$ decays., Comment: 33 pages, 1 figure, 17 tables, typos corrected, contents improved, matching the journal version

We calculate the tree and penguin amplitudes in the $B^0\to\pi^+\pi^-$ decay channel employing the perturbative QCD factorization approach. Using the amplitudes as input with the theoretical uncertainties sufficiently considered, we constrain the UT angle $\gamma$ to $53^\circ\leq\gamma\leq70^\circ$, from the measurements of the CP violation parameters $C_{\pi^+\pi^-}$ and $S_{\pi^+\pi^-}$ in $B^0\to\pi^+\pi^-$. The U-spin breaking effect between $B^0\to\pi^+\pi^-$ and $B_s^0\to K^+K^-$ is estimated to be around 30\%., Comment: 9 pages, 4 figures

We reexamine the branching ratios, $CP$-asymmetries, and other observables in a large number of $B_q\to VV(q=u,d,s)$ decays in the perturbative QCD (PQCD) approach, where $V$ denotes a light vector meson $(\rho, K^*, \omega, \phi)$. 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 $r_i^2=m_{V_i}^2/m_B^2(i=2,3)$ ($m_V$ and $m_B$ 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 $r_i^2$ 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 $B\to \phi K^*$ and $B_s \to \phi\phi$ 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., Comment: one figure, twelve Tables

We study 20 charmless hadronic $B \to f_1 P$ decays in the perturbative QCD(pQCD) formalism with $f_1$ representing axial-vector mesons $f_1(1285)$ and $f_1(1420)$ that result from a mixing of quark-flavor $f_{1q}$ and $f_{1s}$ states with the angle $\phi_{f_1}$. The estimations of branching ratios and CP asymmetries of the considered $B \to f_1 P$ decays are presented in the pQCD approach with $\phi_{f_1} \sim 24^\circ$ from recently measured $B_{d/s} \to J/\psi f_1(1285)$ decays. It is found that (a) the tree(penguin) dominant $B^+ \to f_1 \pi^+(K^+)$ decays with large branching ratios[${\cal O}(10^{-6})$] and large direct CP violations(around 14% $\sim$ 28% in magnitude) simultaneously are believed to be clearly measurable at the LHCb and Belle II experiments; (b) the $B_d \to f_1 K_S^0$ and $B_s \to f_1 (\eta, \eta^{\prime})$ decays with nearly pure penguin contributions and safely negligible tree pollution also have large decay rates in the order of $10^{-6} \sim 10^{-5}$, which can be confronted with the experimental measurements in the near future; (c) as the alternative channels, the $B^+ \to f_1 (\pi^+, K^+)$ and $B_d \to f_1 K_S^0$ decays have the supplementary power in providing more effective constraints on the Cabibbo-Kobayashi-Maskawa weak phases $\alpha$, $\gamma$, and $\beta$ correspondingly, which are explicitly analyzed through the large decay rates and the direct and mixing-induced CP asymmetries in the pQCD approach and are expected to be stringently examined by the measurements with high precision. The complete abstraction can be found in the paper., Comment: revtex file, 25 pages, 6 figures, 4 tables; Matching the published version

We make a systematic investigation on the two-body nonleptonic decays $B_c\rightarrow J/\Psi(\eta_c),M$ by employing the perturbative QCD approach based on $k_T$ factorization, where $M$ is a light pseudoscalar or vector or a heavy charmed meson. We predict the branching ratios and direct CP asymmetries of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow J/\Psi V,J/\psi D^{*}_{(s)}$ decays. It is found that these decays have a large branching ratios of the order of $10^{-4} - 10^{-2}$ and could be measured by the future LHC-b experiment. Our predictions for the ratios of branching fractions $\frac{\mathcal {BR}(B_c^+\rightarrow J/\Psi D_s^+)} {\mathcal {BR}(B_c^+\rightarrow J/\Psi \pi^+)}$ ,$\frac{\mathcal {BR}(B_c^+\rightarrow J/\Psi D_s^{*+})} {\mathcal {BR}(B_c^+\rightarrow J/\Psi D_s^+)}$ and $\frac{\mathcal {BR}(B_c^+\rightarrow J/\Psi K^+)} {\mathcal {BR}(B_c^+\rightarrow J/\Psi \pi^+)}$ are in good agreement with the data. A large transverse polarization fraction which can reach $48\%$ is predicted in $B_c^+\rightarrow J/\Psi D_s^{*+}$ decay, which is consistent with the data. We find a possible direct CP violation in $B_c\rightarrow J/\psi D^{*}$ decays, which are helpful to test the CP violating effects in $B_c$ decays., Comment: 38 pages, 4 figures, 6 tables

We investigate the CP-averaged branching ratios, the polarization fractions, the relative phases, and the CP-violating asymmetries of the penguin-dominated $B \to \phi K_1(1270) $ and $ \phi K_1(1400)$ decays in the perturbative QCD(pQCD) approach, where $K_1(1270)$ and $K_1(1400)$ are believed to be the mixtures of two distinct types of axial-vector $K_{1A}(^3P_1)$ and $K_{1B}(^1P_1)$ states with different behavior, however, their mixing angle $\theta_{K_1}$ is still a hot and controversial topic presently. By numerical evaluations with two different mixing angles $\theta_{K_1} \sim 33^\circ$ and $58^\circ$ and phenomenological analysis, we find that: (a) the pQCD predictions for the branching ratio, the longitudinal polarization fraction and the direct CP violation of $B^\pm \to \phi K_1(1270)^\pm$ decay with the smaller angle $33^\circ$ are in good agreement with the currently available data; (b) though the central values significantly exceed the available upper limit, both pQCD predictions of $Br(B^\pm \to \phi K_1(1400)^\pm)$ with two different mixing angles are consistent with that obtained in QCD factorization and with the preliminary data in 2$\sigma$ errors. These results and other relevant predictions for the considered decays will be further tested by the LHCb and the forthcoming Super-B experiments; (c) the weak annihilation contributions can play an important role in $B \to \phi K_1(1270)$ and $\phi K_1(1400)$ decays; (d) these pQCD predictions combined with the future precision measurements can examine the reliability of the factorization approach employed here, but also explore the complicated QCD dynamics and mixing angle $\theta_{K_1}$ of the axial-vector $K_1(1270)$ and $K_1(1400)$ system., Comment: 19 pages, 1 figure; context enlarged with detailed calculations and corresponding discussions, references added, and the main conclusions remain unchanged; Accepted for publication in Phys.Rev.D

The nonleptonic two body $B_{u,d,s,c}$ decays involving a light tensor meson in final states are studied in the perturbative QCD approach based on $k_T$ factorization. The decay modes with a tensor meson emitted, are prohibited in naive factorization, since the emission diagram with a tensor meson produced from vacuum is vanished. While contributions from the so-called hard scattering emission diagrams and annihilation type diagrams are important and calculable in the perturbative QCD approach. The branching rations of most decays are in the range of $10^{-4}$ to $10^{-8}$, which are bigger by 1 or 2 orders of magnitude than the predictions given by naive factorization, but consistent with the predictions from QCD factorization and the recent experimental measurements. We also give the predictions for the direct $CP$ asymmetries, some of which are large enough for the future experiments to measure. We also find that, even with a small mixing angle, the mixing between $f_2$ and $f_2^{\prime}$ can bring remarkable changes to both branching ratios and the direct $CP$ asymmetries for some decays involving $f_2^{(\prime)}$ mesons. For decays with a vector meson and a tensor meson in final states, we predict a large percentage of transverse polarization contributions due to the contributions of the orbital angular momentum of the tensor mesons., Comment: 19 pages, Invited review for Chinese Science Bulletin

We study two-body hadronic $B_s\to PT$ decays, with $P (T)$ being a light pseudoscalar (tensor) meson, in the perturbative QCD approach. The CP-averaged branching ratios and the direct CP asymmetries of the $\Delta S=0$ modes are predicted, where $\Delta S$ is the difference between the strange numbers of final and initial states. We also define and calculate experimental observables for the $\Delta S=1$ modes under the $B_s^0-\bar{B}_s^0$ mixing, including CP averaged branching ratios, time-integrated CP asymmetries, and the CP observables $C_{f}$, $D_{f}$ and $S_{f}$. Results are compared to the $B_s\to PV$ ones in the literature, and to the $B\to PT$ ones, which indicate considerable U-spin symmetry breaking. Our work provides theoretical predictions for the $B_s\to PT$ decays for the first time, some of which will be potentially measurable at future experiments., Comment: 6 pages, 1 figure

We investigate $B \to K_0^*(1430) K^*$ decays in the perturbative QCD(pQCD) factorization approach, where $B$ denotes $B_u$, $B_d$ and $B_s$ meson respectively, and the scalar $K_0^*(1430)$ is considered as a meson based on the model of conventional two-quark structure. With the light-cone distribution amplitude of $K_0^*(1430)$ defined in two scenarios, namely Scenario 1 and Scenario 2, we make the first estimation for the branching ratios and CP-violating asymmetries for those concerned decay modes in the pQCD factorization approach. For all considered $B \to K_0^*(1430) K^*$ decays in this paper, only one preliminary upper limit on the branching ratio of $B^0 \to {K_0^*(1430)}^0 \bar{K}^{*0}$ measured at 90% C.L. by Belle Collaboration is available now. It is therefore of great interest to examine the predicted physical quantities at two $B$ factories, Large Hadron Collider experiments, and forthcoming Super-$B$ facility, then test the reliability of the pQCD approach employed to study the considered decay modes involving a $p$-wave scalar meson as one of the final state mesons. Furthermore, these pQCD predictions combined with the future precision measurements are also helpful to explore the complicated QCD dynamics involved in the light scalars., Comment: revtex file, 14 pages, 1 figure, contents improved and typos corrected. Accepted for publication in Phys.Rev.D

We study the decay modes of B_{s}^{0}(\bar{B}_{s}^{0})-->D_{s}^{\pm} K^{\mp}, B_{s}^{0}(\bar{B}_{s}^{0})-->D^{\pm} \pi^{\mp} and B^{0}(\bar{B}^{0})-->D^{\pm} \pi^{\mp} in the perterbative QCD approach based on k_T factorization, including the branching ratios and CP violation parameters which provide a clear way to extract the Cabibbo-Kobayashi-Maskawa angle \gamma. Our results of branching ratios of B_{s}^{0}(\bar{B}_{s}^{0})-->D_{s}^{\pm} K^{\mp} and B^{0}(\bar{B}^{0})--> D^{\pm} \pi^{\mp} and the CP asymmetry of B^{0}(\bar{B}^{0})--> D^{\pm} \pi^{\mp} agree well with the experimental data. We also give the predictions of the other observables, which provide some guidance for experiments in the future, especially for LHCb experiment., Comment: 14 pages, 2 figures, 2 tables

The annihilation type diagrams are difficult to calculate in any kind of models or method. Encouraged by the the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we calculate the pure annihilation type $D\to PP(V)$ decays in the perturbative QCD approach based on the $k_T$ factorization. Although the expansion parameter $1/m_D$ is not very small, our leading order numerical results agree with the existing experiment data for most channels. We expect the more accurate observation from experiments, which can help us learn about the dynamics of $D$ meson weak decays., Comment: 5 pages, 1 figure

We study the $B(B_{s})\rightarrow D_{(s)}(\bar{D}_{(s)})\,T$ and $D_{(s)}^{\ast}(\bar{D}_{(s)}^{*})\,T$ decays in perturbative QCD approach, where T denotes a light tensor meson. In addition to the branching ratios, we also give predictions to the polarization fractions for the $D^{*}_{(s)}(\bar{D}_{(s)}^{*})T$ decays. For those decays with a tensor meson emitted, the factorizable emission diagrams do not contribute because of lorentz covariance considerations. In order to give the predictions to these decay channels, it is necessary to go beyond the naive factorization to calculate the nonfactorizable and annihilation diagrams., Comment: 4 pages

In this work, we investigate those $B_{c}\rightarrow D^{(*)}T$ decays in perturbative QCD approach, based on $k_T$ factorization, where T denotes a light tensor meson. For all decays considered in this work, there are no contributions from factorizable emission diagrams because the emitted meson is the tensor meson. We find that the annihilation amplitudes are dominant in these decays due to the large Cabibbo-Kobayashi-Maskawa elements, which are only calculable in the pQCD approach. The numerical results show that the predictions for the branching ratios of most decays are in the order of $10^{-6}$ or even bigger, which can be observed in the ongoing experiments. We also predict large percentage of transverse polarizations in those W annihilation diagram dominant $B_{c} \rightarrow D^{*}T$ decay channels., Comment: 24 pages, 1 figures

In perturbative QCD approach, we investigate the $B(B_{s})\rightarrow D_{(s)}(\bar{D}_{(s)})\,T$ and $D_{(s)}^{*}(\bar{D}_{(s)}^{*})\,T$ decays, which include the Cabibbo-Kobayashi-Maskawa (CKM) favored decays and the Cabibbo-Kobayashi-Maskawa-suppressed decays, where T denotes a light tensor meson. From our calculation, we find that the nonfactorizable emission diagrams and the annihilation type diagrams are important, especially for those color suppressed channels. For those decays with a tensor meson emitted, the factorizable emission diagrams vanish owing to the fact that a tensor meson can not be produced through the local (V-A) or tensor current. The numerical results show that the predictions for the branching ratios of considered charmed B decays are in the range of $10^{-4}$ to $10^{-6}$ for those CKM-favored decays (governed by $|V_{cb}|$) and in the range of $10^{-5}$ to $10^{-8}$ for those CKM-suppressed decays (governed by $|V_{ub}|$). We also predict large transverse polarization contributions in many of the $B(B_{s}) \rightarrow D_{(s)}^{\ast}(\bar{D}_{(s)}^{*})T$ decay channels., Comment: 30 pages, 3 figures, typos correctet in Figs. 1 and 2

We calculate the branching ratios of pure annihilation type decays $B^0\rightarrow D_{s}^{-}K_{2}^{*+}$ and $B_s\rightarrow \bar{D}a_{2}$ using the perturbative QCD approach based on $k_T$ factorization. The branching ratios are predicted to be $(60.6_{-16.5\,-10.4\,-2.1}^{+17.3\,+4.3\,+3.2}) \times 10^{-6}$ for $B^0\rightarrow D_{s}^{-}K_{2}^{*+}$, $(1.1_{-0.4\,-0.2\,-0.1}^{+0.4\,+0.1\,+0.1})\times 10^{-6}$ for $B_s\rightarrow \bar{D}a_{2}^{0}$ and $(2.3_{-0.8\,-0.4\,-0.1}^{+0.8\,+0.2\,+0.1})\times 10^{-6}$ for $B_{s}\rightarrow D^{-}a_{2}^{+}$. They are large enough to be measured in the ongoing experiment. Due to the shortage of contributions from penguin operators, there are no direct CP asymmetries for these decays in the standard model. We also derive simple relations among these decay channels to reduce theoretical uncertainties for the experiments to test the accuracy of theory and search of new physics signal., Comment: 9pages, 1 figure

Two-body charmless hadronic B decays involving a light tensor meson in the final states are studied in the perturbative QCD approach based on $k_T$ factorization. From our calculations, we find that the decay branching ratios for color allowed tree-dominated decays $B\to a_{2}^{0}\pi^{+}$ and $B\to a_{2}^{-}\pi^{+}$ modes are of order $10^{-6}$ and $10^{-5}$, respectively. While other color suppressed tree-dominated decays have very small branching ratios. In general, the branching ratios of most decays are in the range of $10^{-5}$ to $10^{-8}$, which are bigger by one or two orders of magnitude than those predictions obtained in Isgur-Scora-Grinstein-Wise II model and in the covariant light-front approach, but consistent with the recent experimental measurements and the QCD factorization calculations. Since the decays with a tensor meson emitted from vacuum are prohibited in naive factorization, the contributions of nonfactorizable and annihilation diagrams are very important to these decays, which are calculable in our perturbative QCD approach. We also give predictions to the direct CP asymmetries, some of which are large enough for the future experiments to measure. Because we considered the mixing between $f_{2}$ and $f_{2}'$, the decay rates are enhanced significantly for some decays involving $f_{2}^{\prime}$ meson, even with a small mixing angle., Comment: 26 pages, 2 figures

We make a systematic investigation on the two-body nonleptonic decays B_c {\to} D^{(*)}_{(s)}P, D^{(*)}_{(s)}V, by employing the perturbative QCD approach based on k_T factorization, where P and V denote any light pseudoscalar meson and vector meson, respectively. We predict the branching ratios and direct CP-asymmetries of these B_c decays and also the transverse polarization fractions of B_c {\to} D^{*}_{(s)}V decays. It is found that the non-factorizable emission diagrams and annihilation type diagrams have remarkable effects on the physical observables in many channels, especially the color-suppressed and annihilation-dominant decay modes. A possible large direct CP-violation is predicted in some channels; and a large transverse polarization contribution that can reach 50% ~ 70% is predicted in some of the Bc {\to} D^{*}_{(s)}V decays., Comment: 28 pages, 5 tables, to appear at PRD

Based on the assumption of two-quark structure of the scalar $K_0^*(1430)$, the CP-averaged branching ratios(BRs) and CP-violating asymmetries of charmless hadronic $B_q(q=u,d,s,c) \to \kst \kstb$ decays are studied in the standard model(SM) by employing the perturbative QCD(pQCD) factorization approach. Our predictions are the following: (1) the CP-averaged BRs for $B_{q} \to \kst \kstb$ decays in both scenarios vary in the range of $10^{-6} \sim 10^{-4}$ in the SM; (2) the magnitudes of $\acp^{\rm dir}(B_u \to {\kst}^+ {\kstb}^0)$ and $\acp^{\rm dir}(B_{d,s} \to {\kst}^+ {\kst}^-)$ in Scenario 1 are much larger than those in Scenario 2 correspondingly; (3) there are no direct CP violations in $B_{d,s} \to {\kst}^0 {\kstb}^0$ and $B_c \to {\kst}^+ {\kstb}^0$ decays in the SM because of the pure penguin and tree topology, respectively. A measurement of our pQCD predictions at the predicted level will favor the $q\bar q$ structure of the scalar $\kst$ and help us to understand its physical properties and the involved QCD dynamics., Comment: 23 pages, 1 figure, references added and discussions improved