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Preclinical and clinical studies have suggested a neuroprotective effect of remote ischemic conditioning (RIC), which involves repeated occlusion/release cycles on bilateral upper limb arteries; however, robust evidence in patients with ischemic stroke is lacking.To assess the efficacy of RIC for acute moderate ischemic stroke.This multicenter, open-label, blinded-end point, randomized clinical trial including 1893 patients with acute moderate ischemic stroke was conducted at 55 hospitals in China from December 26, 2018, through January 19, 2021, and the date of final follow-up was April 19, 2021.Eligible patients were randomly assigned within 48 hours after symptom onset to receive treatment with RIC (using a pneumatic electronic device and consisting of 5 cycles of cuff inflation for 5 minutes and deflation for 5 minutes to the bilateral upper limbs to 200 mm Hg) for 10 to 14 days as an adjunct to guideline-based treatment (n = 922) or guideline-based treatment alone (n = 971).The primary end point was excellent functional outcome at 90 days, defined as a modified Rankin Scale score of 0 to 1. All end points had blinded assessment and were analyzed on a full analysis set.Among 1893 eligible patients with acute moderate ischemic stroke who were randomized (mean [SD] age, 65 [10.3] years; 606 women [34.1%]), 1776 (93.8%) completed the trial. The number with excellent functional outcome at 90 days was 582 (67.4%) in the RIC group and 566 (62.0%) in the control group (risk difference, 5.4% [95% CI, 1.0%-9.9%]; odds ratio, 1.27 [95% CI, 1.05-1.54]; P = .02). The proportion of patients with any adverse events was 6.8% (59/863) in the RIC group and 5.6% (51/913) in the control group.Among adults with acute moderate ischemic stroke, treatment with remote ischemic conditioning compared with usual care significantly increased the likelihood of excellent neurologic function at 90 days. However, these findings require replication in another trial before concluding efficacy for this intervention.ClinicalTrials.gov Identifier: NCT03740971.

Background Dual antiplatelet therapy is considered beneficial in acute ischemic stroke (AIS) patients with intracranial artery stenosis (ICAS), with more bleeding events. Ginkgolide is shown to reduce platelet activation after infarction, which might be of benefit in AIS. We aimed to explore the effect of Ginkgolide in AIS patients with ICAS. Methods This was a randomized, double‐blinded, placebo‐controlled trial conducted at 61 centers in China. Within 72 h after onset, consecutive patients diagnosed as AIS with ICAS were randomized to either Ginkgolide or placebo treatment. The primary outcome was the composite of mortality and recurrent stroke (ischemic or hemorrhagic) during first 4 weeks in an intention‐to‐treat analysis. Secondary functional outcome was assessed by modified Rankin Scale and improvement of stroke severity was assessed by National Institution of Health Stroke Scale at day 28. Safety outcome was measured by the rate of severe adverse event (SAE). Results There were 936 patients randomized to either Ginkgolide or placebo treatment. Their average age was 64.2 ± 10.4 years old and 36.0% of the patients were female. The composite index event occurred in six patients in placebo group, and none occurred in Ginkgolide group (risk ratio 1.01; 95% CI 1.00–1.02). There were more patients who achieved favorable outcome in Ginkgolide group, compared with that of the placebo group (OR 2.16, 95%CI 1.37–3.41). SAE occurred in five (1.1%) patients in the Ginkgolide group and three (0.6%) in the placebo group (OR0.60, 95CI% 0.14–2.53). Intracranial hemorrhage occurred in 1/473 (0.2%) in the placebo group. Conclusions Ginkgolide, working as PAF antagonist, may reduce recurrent stroke in AIS with ICAS patients within 72 hours after onset. It might be an optional treatment in moderate‐to‐severe AIS patients with ICAS. (http://www.chictr.org.cn Number as ChiCTR‐IPR‐17012310)., Although dual antiplatelet therapy is considered benefit in acute ischemic stroke (AIS) patients with intracranial artery stenosis (ICAS), there are more bleeding events. Ginkgolide, works as PAF antagonist, may reduce recurrent and mortality in AIS with large artery stenosis within 72 hours atfer onset during 90 days follow‐up. It might play a role of neuroprotection in AIS patients with ICAS

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 approach's 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., 22 pages, 3 figures, 5 tables

The discovery of has inspired new interest in studying doubly heavy baryons. In this study, the weak decays of a doubly charmed baryon to a light baryon and a charm meson (either a pseudoscalar or a vector one) are calculated. Following our previous work, we calculate the short distance contributions under the factorization hypothesis, whereas the long distance contributions are modeled as the final state interactions, which are calculated with the one particle exchange model. We find that the decays' branching ratios are obviously larger, as they receive contributions of more polarization states. Among the decays that we investigate, the following have the largest branching fractions: estimated with fs; and with fs; and , , and with fs. By comparing the decay widths of pure color commensurate channels with those of pure bow-tie ones, we find that the bow-tie mechanism plays an important role in charm decays.

In this work, the full leading order results of the form factors for $$\Xi _{b}\rightarrow \Xi _{c}$$ Ξ b → Ξ c and $$\Lambda _{b}\rightarrow \Lambda _{c}$$ Λ b → Λ c are obtained in QCD sum rules. Contributions from up to dimension-5 have been considered. For completeness, we also study the two-point correlation function to obtain the pole residues of $$\Xi _{Q}$$ Ξ Q and $$\Lambda _{Q}$$ Λ Q , and higher accuracy is achieved. For the three-point correlation function, since stable Borel regions cannot be found, about $$20\%$$ 20 % uncertainties are introduced for the form factors of $$\Xi _{b}\rightarrow \Xi _{c}$$ Ξ b → Ξ c and $$\Lambda _{b}\rightarrow \Lambda _{c}$$ Λ b → Λ c . Our results for the form factors are consistent with those of the lattice QCD within errors.

The weak decays of a spin-1 / 2 doubly charm baryon ( $$\mathcal{B}_{cc}$$ ) to a spin-1 / 2 singly charm baryon ( $$\mathcal{B}_c$$ ) and a light vector meson (V) are studied under a phenomenological scheme. The contributions are classified into different topological diagrams, among which the short distance ones are calculated under the factorization hypothesis, and the long distance contributions are modelled as final-state interactions (FSIs) which are estimated with the one-particle-exchange model. In calculation the topological contributions tend to fall in a hierarchy. The branching fractions or decay widths are estimated, and it indicates that $$\Xi _{cc}^+\rightarrow \Xi _c^+\pi ^+\pi ^-$$ and $$\Omega _{cc}^{+}\rightarrow \Xi _{c}^{+}K^-\pi ^+$$ can be used as candidate decays for searching $$\Xi _{cc}^+$$ and $$\Omega _{cc}^+$$ . Some decays that are mainly activated by the long distance effects are found, observation on which in future experiments can help to understand the role of FSIs in charm baryon decays.

Background: A neuroprotective effect of nimodipine on acute cerebral infarction has been confirmed, but there are few reports regarding the therapeutic effect of nimodipine on acute massive cerebral infarction. There is also no consensus on the optimal time window for the use and dosage of nimodipine. This trial is planned to answer these questions using a double-blind randomized controlled design. Methods/Design: This is a double-blind randomized controlled trial. The experiments will be conducted in the Department of Neurology, Central Hospital Affiliated to Shenyang Medical College of China. One hundred patients with acute massive cerebral infarction will be randomly assigned to a control group and a treatment group. Patients in the control and treatment groups will receive intravenous infusion of citicoline and intravenous infusion of nimodipine (10 mg/d) respectively, for 7 consecutive days. Simultaneously, to determine the appropriate time window for treatment with nimodipine, patients in the treatment group will be divided into four subgroups according to the time of nimodipine administration: < 3 hours, 3-6 hours, 6-24 hours, and > 24 hours. The main outcome measures are: the National Institutes of Health Stroke Scale and the Rankin scale will be used to assess the severity and recovery of neurological impairment, respectively. Cranial computed tomography and magnetic resonance imaging will be used to evaluate brain lesions and the Barthel index will be used to assess the activities of daily living. Secondary outcome measures are heart rate and blood pressure. Discussion: It is hoped that the experimental results can determine the best application time window and dosage of nimodipine for acute massive cerebral infarction. Trial registration: ClinicalTrials.gov identifier: NCT02248233; registered on 22 September 2014.

Within the framework of the perturbative QCD approach, we calculate the time-like $B_cB_c(B_c^*)$ form factors $F(Q^2)$ and $A_2(Q^2)$. We include relativistic corrections and QCD corrections, either of which can give about $20\%$ correction to the leading-order contribution, but there are cancellation effects between them. We calculate the cross sections of the $e^+e^-\to B_c^-B_c^+(B_c^{*+})$ processes. The cross sections are enhanced at the $Z$ pole to be $\sigma^{PP}(Q=m_Z) \sim 1.3\times10^{-5}\text{pb}$ and $\sigma^{PV}(Q=m_Z) \sim 2.5\times10^{-5}\text{pb}$, which are still too small to be detected by proposed $e^+e^-$ colliders such as the Circular Electron Positron Collider.

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 ${B}_{c}\ensuremath{\rightarrow}{K}_{2}^{*}(1430)K$ and the CKM-favored ${B}_{c}\ensuremath{\rightarrow}TV$---have large decay rates of ${10}^{\ensuremath{-}6}$, which are expected to be detected at Large Hadron Collider experiments in the near future. Moreover, all of the ${B}_{c}\ensuremath{\rightarrow}TV$ 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.

The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, $\Xi_{cc}^{++}$ and $\Xi_{cc}^{+}$, which would be helpful for experimental searches for these particles. The branching fractions are studied under the factorization hypothesis for the short-distance contributions and considering the rescattering effect for the long-distance contributions which are significantly enhanced. Comparing all the decay modes, we recommend the processes of $\Xi_{cc}^{++}\to \Lambda_c^+K^-\pi^+\pi^+$ and $\Xi_c^+\pi^+$ as the first priority for experiments to search for the doubly heavy baryons., Comment: 16 pages, 3 figure, 5 tables. Version to be published in CPC

In a combined investigation of the $B\to K^{(*)}\ell^+\ell^-$ decays, constraints on the related couplings in family non-universal $Z^{\prime}$ models are derived. We find that within the allowed parameter space, the recently observed forward-backward asymmetry in the $B\to K^*\ell^+\ell^-$ decay can be explained, by flipping the signs of the Wilson coefficients $C_9^{\rm eff}$ and $C_{10}$. With the obtained constraints, we also calculate the branching ratio of the $B_s\to\mu^+\mu^-$ decay. The upper bound of our prediction is near the upper bound given by CDF Collaboration recently.

$B^\pm \to (D^0, \bar D^0, D_{CP})K^{*\pm}_{0,2}$ decays are helpful in determining the CP violation angle $\gamma$, and we analyze these decay processes within the perturbative QCD approach based on $k_T$ factorization. We found that the branching ratio of $B^-\to D^0 K^{*-}_0$ can reach the order of $10^{-4}$, due to the enhancement of nonfactorizable contributions in color-suppressed $D^0$-emission, while the branching ratio of $B^-\to \bar D^0 K^{*-}_0$ is of the order $10^{-5}$. The ratio of decay amplitudes is about 3 times larger than the one in the channel $B^\pm\to D K^\pm$. Large branching ratios provide a good opportunity to observe $ B^\pm \to D K^{*\pm}_2$ on the ongoing and forthcoming experimental facilities and consequently these channels may be of valuable avail in reducing the errors in the CP violation phase angle $\gamma$. We also explore the possible time-dependent CP asymmetries of $B_s$ decay into a scalar meson to determine the phase angle $\gamma$.

Motivated by the experimental data, we study charmless B-u,B-d,B-s -> VT (V and T denote light vector and tensor mesons, respectively) decays in the perturbative QCD approach. The predictions of branching ratios, polarization fractions, and direct CP violations are given in detail. Specifically, within this approach we have calculated the polarization fractions and the branching ratios of B -> phi(K-2(*-), (K) over bar (*-0)(2)) which agree well with the observed experimental data; however, the branching ratios of B -> omega(K-2(*-), (K) over bar (*-0)(2)) are hard to be explained, where the polarization fractions are well accommodated. The tree dominated channels with a vector meson emitted have a longitudinal polarization fraction of 90%, while the penguin dominating ones have subtle polarization fractions. Fortunately, most branching ratios of B-u,B-d decays are of the order 10(-6), which would be straightforward for experimental observations. For the B-s decays the branching ratios can reach the order of 10(-6) in tree dominated decays, while in penguin dominated decays those are of the order of 10(-7) which require more experimental data to be observed.

Within the perturbative QCD approach and ignoring the contributions of long distance and subleading penguin loops, we investigate $\bar B^0 \to D^0 \mu^+\mu^-$ decay in the large recoiling kinematic region in the Standard Model. At the tree level, $\bar B^0$ decays to $D^0$ by exchanging a $W$ boson accompanied by a virtual photon emission from the valence quarks of $\bar B^0$ and $D^0$ meson, then the virtual photon decays to the lepton pair. Numerically, we find that the branching ratio decreases rapidly as the $q^2$ increases, and the branching ratio of $ \bar B^0\to D^0\mu^+\mu^-$ is $(9.7_{-3.2}^{+4.2})\times 10^{-6}$ in the region $q^2 \in [1,5] \mathrm{GeV}^2$. The order of the branching ratio shows a possibility to study this interesting channel in the current $B$ factories and the Large Hadron Collider. The precise experimental data will help us to test the factorization approach and the QCD theory, in general., Comment: 9 pages, 5 figures, Final version to be published in JHEP

We analyze the $B\ensuremath{\rightarrow}{K}_{2}^{*}(\ensuremath{\rightarrow}K\ensuremath{\pi}){l}^{+}{l}^{\ensuremath{-}}$ (with $l=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$) decay in the standard model and two new physics scenarios: the vectorlike quark model and family nonuniversal ${Z}^{\ensuremath{'}}$ models. We derive the differential angular distributions using the recently calculated form factors in the perturbative QCD approach. Branching ratios, polarizations, forward-backward asymmetries, and transversity amplitudes are predicted, from which we find a promising prospective to observe this channel in future experiments. We update the constraints on effective Wilson coefficients and/or free parameters in these two new physics scenarios by making use of the $B\ensuremath{\rightarrow}{K}^{*}{l}^{+}{l}^{\ensuremath{-}}$ and $b\ensuremath{\rightarrow}s{l}^{+}{l}^{\ensuremath{-}}$ experimental data. Their impact on $B\ensuremath{\rightarrow}{K}_{2}^{*}{l}^{+}{l}^{\ensuremath{-}}$ is subsequently explored and, in particular, the zero-crossing point for the forward-backward asymmetry in these new physics scenarios can sizably deviate from the standard model. In addition we also generalize the analysis to a similar mode, ${B}_{s}\ensuremath{\rightarrow}{f}_{2}^{\ensuremath{'}}(1525)(\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}){l}^{+}{l}^{\ensuremath{-}}$.

The factorization theorem in Decays of $B_{(s)}$ mesons to two charmed mesons (both pseudoscalar and vector) can still be proved in the leading order in $m_D/m_B$ and $\Lambda_{\rm{QCD}}/m_D$ expansion. Working in the perturbative QCD approach, we find that the factorizable emission diagrams are dominant. Most of branching ratios we compute agree with the experimental data well, which means that the factorization theorem seems to be reliable in predicting branching ratios for these decays. In the decays of a $B$ meson to two vector charmed mesons, the transverse polarization states contribute $40%-50%$ both in the processes with an external W emission and in the pure annihilation decays. This is in agreement with the present experimental data. We also calculate the CP asymmetry parameters. The results show that the direct CP asymmetries are very small. Thus observation of any large direct CP asymmetry will be a signal for new physics. The mixing induced CP asymmetry in the neutral modes is large. This is also in agreement with the current experimental measurements. They can give a cross check of the $\sin 2\beta$ measurement from other channels., Comment: 28 pages, 3 figures, version appeared in PRD

The transition form factors of ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(2317)$ and ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(1968)$ at large recoil region are investigated in the light cone sum rules approach, where the heavy quark effective theory is adopted to describe the form factors at small recoil region. With the form factors obtained, we carry out a detailed analysis on both the semileptonic decays ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(1968,2317)l{\overline{\ensuremath{\nu}}}_{l}$ and nonleptonic decays ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{+}(1968,2317)M$ with $M$ being a light meson or a charmed meson under the factorization approach. Our results show that the branching fraction of ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(2317)\ensuremath{\mu}{\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ is around $2.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which should be detectable with ease at the Tevatron and CERN LHC. It is also found that the branching fractions of ${\overline{B}}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(1968)l{\overline{\ensuremath{\nu}}}_{l}$ are almost 1 order larger than those of the corresponding ${B}_{s}^{0}\ensuremath{\rightarrow}{D}_{s}^{+}(2317)l{\overline{\ensuremath{\nu}}}_{l}$ decays. The consistency of predictions for ${B}_{s}\ensuremath{\rightarrow}{D}_{s}^{+}(1968,2317)L$ ($L$ denotes a light meson) in the factorization assumption and ${k}_{T}$ factorization also supports the success of color transparency mechanism in the color allowed decay modes. Most two-charmed meson decays of ${B}_{s}$ mesons possess quite large branching ratios that are accessible in the experiments. These channels are of great importance to explore the hadronic structure of charmed mesons as well as the nonperturbative dynamics of QCD.

The B{sub u,d,s}{yields}V, A form factors are studied in the perturbative QCD approach (V, A denote a vector meson and two kinds of p-wave axial-vector mesons: {sup 3}P{sub 1} and {sup 1}P{sub 1} states, respectively). The form factors are directly studied in the large recoiling region and extrapolated to the whole kinematic region within the dipole parametrization. Adopting decay constants with different signs for the two kinds of axial vectors, we find that the two kinds of B{yields}A form factors have the same sign. The two strange mesons K{sub 1A} and K{sub 1B} mix with each other via the SU(3) symmetry breaking effect. In order to reduce the ambiguities in the mixing angle between K{sub 1A} and K{sub 1B}, we propose a model-independent way that utilizes the B decay data. Most of the branching fractions of the semilteptonic B{yields}Al{nu}{sub l} decays are of the order 10{sup -4}, which still need experimental tests in the ongoing and forthcoming experiments.

Under two different scenarios for the light scalar mesons, we investigate the transition form factors of $B({B}_{s})$ mesons decay into a scalar meson in the perturbative QCD approach. In the large recoiling region, the form factors are dominated by the short-distance dynamics and can be calculated using perturbation theory. We adopt the dipole parametrization to recast the ${q}^{2}$ dependence of the form factors. Since the decay constants defined by the scalar current are large, our predictions on the $B\ensuremath{\rightarrow}S$ form factors are much larger than the $B\ensuremath{\rightarrow}P$ transitions, especially in the second scenario. Contributions from various light-cone distribution amplitudes (LCDAs) are elaborated and we find that the twist-3 LCDAs provide more than one-half of the contributions to the form factors. The two terms of the twist-2 LCDAs give destructive contributions in the first scenario while they give constructive contributions in the second scenario. With the form factors, we also predict the decay width and branching ratios of the semileptonic $B\ensuremath{\rightarrow}Sl\overline{\ensuremath{\nu}}$ and $B\ensuremath{\rightarrow}S{l}^{+}{l}^{\ensuremath{-}}$ decays. The branching ratios of $B\ensuremath{\rightarrow}Sl\overline{\ensuremath{\nu}}$ channels are found to have the order of ${10}^{\ensuremath{-}4}$ while those of $B\ensuremath{\rightarrow}S{l}^{+}{l}^{\ensuremath{-}}$ have the order of ${10}^{\ensuremath{-}7}$. These predictions can be tested by the future experiments.

We investigate the $B\ensuremath{\rightarrow}{a}_{1}(1260)({b}_{1}(1235))\ensuremath{\pi}(K)$ decays under the factorization scheme and find many discrepancies between theoretical predictions and the experimental data. In the tree-dominated processes, large contributions from color-suppressed tree diagrams are required in order to accommodate the large decay rates of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$. For ${\overline{B}}^{0}\ensuremath{\rightarrow}({a}_{1}^{+},{b}_{1}^{+}){K}^{\ensuremath{-}}$ decays which are induced by $b\ensuremath{\rightarrow}s$ transition, theoretical predictions on their decay rates are larger than the data by a factor of 2.8 and 5.5, respectively. Large electroweak penguins or some new mechanism are expected to explain the branching ratios of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{b}_{1}^{0}{K}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\overline{K}}^{0}$. The soft-collinear effective theory has the potential to explain large decay rates of ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{0}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}{a}_{1}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ via a large hard-scattering form factor ${\ensuremath{\zeta}}_{J}^{B\ensuremath{\rightarrow}{a}_{1}}$. We will also show that, with proper charming penguins, predictions on the branching ratios of ${\overline{B}}^{0}\ensuremath{\rightarrow}({a}_{1}^{+},{b}_{1}^{+}){K}^{\ensuremath{-}}$ can also be consistent with the data.

Two-body charmed decays B{sub (s)}{yields}D{sub (s)}P, D{sub (s)}*P, D{sub (s)}V, and D{sub (s)}*V, where P and V denote the light pseudoscalar meson and vector meson, respectively, are analyzed in the perturbative QCD (pQCD) approach. Using the experimental data of six B{yields}DP channels, we test the D meson wave function by {chi}{sup 2} fit. We give the branching ratios of all the charmed B decay channels, most of which agree with experiments amazingly well. The predicted B{sub s} decays can be confronted with the future experimental data. By straightforward calculations, our pQCD approach gives the right relative strong phase of a{sub 2}/a{sub 1} that agrees with experiments. We also predict the percentage of transverse polarizations in B{sub (s)}{yields}D*V decay channels.

The recent Tevatron result on the top quark forward-backward asymmetry, which deviates from its standard model prediction by 3.4$\sigma$, has prompted many authors to build new models to account for this anomaly. Among the various proposals, we find that those mechanisms which produce $t\bar t$ via $t$- or $u$-channel can have a strong correlation to the rare B decays. We demonstrate this link by studying a model with a new charged gauge boson, $W'$. In terms of the current measurements on $B\to \pi K$ decays, we conclude that the branching ratio for $B^-\to \pi^- \bar K^0$ is affected most by the new effects. Furthermore, using the world average branching ratio for the exclusive B decays at $2\sigma$ level, we discuss the allowed values for the new parameters. Finally, we point out that the influence of the new physics effects on the direct CP asymmetry in B decays is insignificant., Comment: 15 page, 6 figures, typos corrected and references added, final version to appear journal

Although the two-body charmed decays $B_{(s)} \to \bar D_{(s)}^{(*)}P$ and $\bar D_{(s)}^{(*)}V$, where $P$($V$) denotes a light pseudoscalar(vector) meson, are CKM suppressed comparing with the $B_{(s)} \to D_{(s)}^{(*)}P$ and $ D_{(s)}^{(*)}V$ decays, they are important in the CKM angle $\gamma=\phi_3$ extraction method. We investigated these decays in the perturbative QCD approach to the leading order of $m_D/m_B$ and $\Lambda_{\rm{QCD}}/m_D$ expansion. We find that the nonfactorizable emission diagrams and the annihilation diagrams are not negligible in many of these channels. The numerical results show that most channels have branching ratios with an order of $10^{-6}$ or $10^{-7}$. The ratio needed for the CKM angle $\gamma$ extraction is estimated as $r = \frac{|A(B^- \to \bar{D}^0 K^-)|}{|A(B^- \to D^0 K^-)|} = 0.092_{-0.003-0.003}^{+0.012+0.003},$ which is too small for the experiments. Some of the $ B_{(s)}\to \bar D_{(s)}^*V$ decays have a very large transversely polarized contribution that can reach 80%.