In this paper, we calculate the branching ratio and direct CP asymmetry parameter of $B_c^{\pm}\to D^{0}K^{\pm}$ in the framework of perturbative QCD approach based on $k_T$ factorization. Besides the usual factorizable diagrams, both non-factorizable and annihilation type contributions are taken into account. We find that (a) the branching ratio is at the order of $10^{-5}$; (b) the tree annihilation diagrams and the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry is about 7%, which can be tested in the Large Hadron Collider beauty experiments (LHC-b) at CERN.
Working in a perturbative QCD model approach, we obtain the essential form factor of the radiative transition $B \rightarrow V^{*} γ$ and estimate the branching ratio $BR(B \rightarrow K^{*} γ)$. The results are determined by a parameter expressing the momentum distribution in the $B$ - meson wave function. Our estimations are compared to other theoretical predictions as well as to experimental data.
The radiative B -> K* gamma mode is caused by a penguin operator which is a quantum correction. Thus this mode may be useful in the search for physics beyond the standard model. In this paper, we compute the branching ratio, direct CP asymmetry, and isospin breaking effects within the Standard Model in the framework perturbative QCD, and discuss how new physics might show up in this decay.
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 $|V_{ub}^* V_{cd}|$.
The most precise measurement of the $CP$ asymmetry in the decay $B^-\rightarrow D_s^-D^0$ has been reported by LHCb collaboration with the value of $(-0.4\pm0.5\pm0.5)\%$. In this study, the $CP$ violation in the decay $B^-\rightarrow D_s^-D^0$ has been calculated under the factorization approach. This decay mode includes current-current tree and penguin diagrams and their amplitudes are considered separately. In each of the tree and penguin amplitudes, the strong and weak phases have been introduced. The $CP$ asymmetry has been calculated in this work to be $(-0.35\pm0.03)\%$. Finally, from t…
In this work we study the CP violation for $\bar{B^0}\to J/ψK_s$ and $\bar{B^0}\to ϕK_s$ up to leading and next-to-leading order QCD corrections in the standard model, two-Higgs-doublet model and the minimal supersymmetric extension of the standard model. We also study the effect of new physics on the branching ratios of these two decay modes. We find that within the parameter space constrained by the observation of the decay $b\to sγ$, new physics does not affect the CP asymmetries greatly, and the prediction of new physics to the branching ratios of $\bar{B^0}\to J/ψK_s$ and $\bar{B^0}\to ϕK…
We calculate the branching ratios and CP asymmetries for B^0 to pi^+pi^-, B^+ to pi^+pi^0 and B^0 to pi^0pi^0 decays, in a perturbative QCD approach. In this approach, we calculate non-factorizable and annihilation type contributions, in addition to the usual factorizable contributions. We found that the annihilation diagram contributions are not very small as previous argument. Our result is in agreement with the measured branching ratio of B to pi^+pi^- by CLEO collaboration. With a non-negligible contribution from annihilation diagrams and a large strong phase, we predict a large direct CP …
We present a novel dynamics for generating sizable CP-violating asymmetries in the decays of charged $B^\mp\to π^\mp ω, π^\mpρ^0, π^0ρ^\mp$, and in $\bar{B^0}(B^0)\toπ^\mpρ^\pm$. The dynamics for the necessary final-state interactions involves the mixing of G-parity eigenstates of the system $(\bar{D}^*D,D^*\ol{D})$ with the $G=\pm 1$ states of $πω$ and $πρ$, respectively. The dynamical effect is enhanced by the empirically large branching ratio for decays to $(\bar{D}^*D,D^*\bar{D})$. A correlated result is a markedly enhanced branching ratio for $\bar{B^0}(B^0)\toπ^0ρ^0$, which has now been …
We show that few-percent Okubo-Zweig-Iizuka-rule violating effects in the quark-flavor basis for the $η$-$η'$ mixing can enhance the chiral scale associated with the $η_q$ meson few times. This enhancement is sufficient for accommodating the dramatically different data of the $B\toη^{\prime} K$ and $B\toηK$ branching ratios. We comment on other proposals for resolving this problem, including flavor-singlet contributions, axial U(1) anomaly, and nonperturbative charming penguins. Discrimination of the above proposals by means of the $B\toη^{(\prime)}\ellν$ and $B_s\toη^{(\prime)}\ell\ell$ data …
In Perturbative QCD (PQCD) approach we study the direct $CP$ violation in the pure annihilation decay process of $\bar{B}^0_{s}\rightarrowπ^+π^-π^+π^-$ induced by the $ρ$ and $ω$ double resonance effect. Generally, the $CP$ violation is small in the pure annihilation type decay process. However, we find that the $CP$ violation can be enhanced by double $ρ-ω$ interference when the invariant masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance. For the decay process of $\bar{B}^0_{s}\rightarrowπ^+π^-π^+π^-$, the maximum $CP$ violation can reach 28.64{\%}.
In the perturbative QCD (PQCD) approach we study the direct $CP$ violation in $B^+_{c}\rightarrow D_{(s)}^+ρ^0(ω) \rightarrow D_{(s)}^+π^+π^-$ via the $ρ-ω$ mixing mechanism. We find that the $CP$ violation can be enhanced by $ρ-ω$ mixing when the invariant masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance. For the decay process $B^+_{c}\rightarrow D^+ρ^0(ω) \rightarrow D^+π^+π^-$, the maximum $CP$ violation can reach 7.5 {\%}.
In perturbative QCD approach, we study the direct $CP$ violation in the decay of $\bar{B}_s^0\toρ(ω)ϕ\to {π^+}{π^-}ϕ$ via isospin symmetry breaking. An interesting mechanism involving the charge symmetry violating between $ρ$ and $ω$ is applied to enlarge the $CP$ violating asymmetry. We find that the $CP$ violation can be enhanced by the $ρ-ω$ mixing mechanism when the invariant masses of the $π^+π^-$ pairs are in the vicinity of the $ω$ resonance. For the decay process of $\bar{B}^0_{s}\toρ(ω)ϕ\to{π^+}{π^-}ϕ$, the maximum $CP$ violation can reach $5.98\%$. The possibility of detecting the $C…
In this note, we calculate the branching ratio of B_c\to J/ψK in the framework of perturbative QCD approach based on k_T factorization. This decay can occur only via tree level diagrams in the Standard Model. We find that the branching ratio of B_c\to J/ψK is about (1-3)\times10^{-4}. The large branching ratio and the clear signals of the final states make the measurement of B_c\to J/ψK easily at LHC-b experiments.
The effects of perturbative Lorentz and CPT violation on neutrino oscillations are studied. Features include neutrino-antineutrino oscillations, direction dependence, and unconventional energy behavior. Leading-order corrections arising from renormalizable operators are derived in the general three-flavor effective field theory. The results are applied to neutrino-beam experiments with long baselines, which offer excellent sensitivity to the accompanying effects. Key signatures of Lorentz and CPT violation using neutrino beams include sidereal variations in the oscillation probabilities arisin…
We calculate the branching ratios and CP asymmetries of the $B\to ϕK$ decays using perturbative QCD approach, which includes $k_T$ and threshold resummations. Our results of branching ratios are consistent with the experimental data and larger than those obtained from the naive factorization assumption and the QCD-improved factorization approach.
We study the rare decays $B^+ \to D^{(*)+}K^{(*)0}$, which can occur only via annihilation type diagrams in the standard model. We calculate all of the four modes, $B \to PP, VP, PV, VV$, in the framework of perturbative QCD approach and give the branching ratios of the order about $10^{-6}$.
The top quark decay process $\tcups$ is studied in the Standard Model and the Minimal Supersymmetric Standard Model with conserved and violated $R-$parity. In dealing with the heavy quarkonium, $\ups$, production, we take both color-singlet and -octet mechanisms into consideration. With numerical analysis it is found that within the Standard Model the decay rate of the concerned process is beyond the border of reachable level of the next round of experiment, though it is much larger than that of the rare top decays, while extra new contributions from beyond the Standard Model could enhance the…
A recently proposed Non-Standard Model solution to the problem of low semileptonic branching ratio B_{SL} which suggests a large branching ratio for the decay $b \to sg$ is critically examined. It is shown that the effects of the Enhanced Chromomagnetic Dipole Operator might lead to significant violations of isospin symmetry in rare radiative decays of B-mesons.
In this work, we study the localized $CP$ violation and the branching fraction of the four-body decay $\bar{B}^0\rightarrow K^-π^+π^-π^+$ by employing a quasi-two-body QCD factorization approach. Considering the interference of $\bar{B}^0\rightarrow \bar{K}_0^*(700)ρ^0(770)\rightarrow K^-π^+π^-π^+$ and $\bar{B}^0\rightarrow \bar{K}^*(892)f_0(500)\rightarrow K^-π^+π^-π^+$ channels, we predict $\mathcal{A_{CP}}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[0.15,0.28]$ and $\mathcal{B}(\bar{B}^0\rightarrow K^-π^+π^-π^+)\in[1.73,5.10]\times10^{-7}$, respectively, which shows that this two channels' interf…
We calculate all the branching ratios and direct CP violations of $B \to PV$ decays in a most general two-Higgs-doublet model with spontaneous CP violation. As the model has rich CP-violating sources, it is shown that the new physics effects to direct CP violations and branching ratios in some channels can be significant when adopting the generalized factorization approach to evaluate the hadronic matrix elements, which provides good signals for probing new physics beyond the SM in the future B experiments.
It is shown that intrinsic neutrino flavor violation invariably occurs when neutrinos are created within the SM augmented by the known massive neutrinos, with mixing and nondegenerate masses. The effects are very small but much greater than the naive estimate $Δm^2/E_ν^2$ or the branching ratio of indirect flavor violating processes such as $μ\to eγ$ within the SM. We specifically calculate the probability (branching ratio) of pion decay processes with flavor violation, such as $π\to μ\barν_e$, showing nonzero results.
The branching ratios for the neutral and charged B decay channels to $η' K$ and $ηK^*$ are well above the Standard Model expectations. Moreover, the mixing-induced CP asymmetry in $B \to ϕK_S$ is incompatible to that found in $B\to J/ψK_S$. We investigate whether a flavour-specific tree-level $b\to s \bar{s} s$ operator coming from R-parity violating supersymmetry can resolve both these discrepancies, without jeopardizing those results which are in agreement with the Standard Model. We found that it is possible to have a parameter space satisfying all these requirements, including that of a lo…
Recent measurements of B^0 -> pi pi decays reveal two features that are in conflict with conventional calculations: the channel B^0 (Bbar^0) -> pi^+ pi^- shows a large direct CP-violating asymmetry, and the channel B^0 (B^0) -> pi^0 pi^0 has an unexpectedly high branching ratio. We show that both features can be understood in terms of strong-interaction mixing of pi pi and D Dbar channels in the isospin-zero state, an effect that is important because of the large experimentally observed ratio Gamma(B^0 / Bbar^0 -> D^+ D^-) / Gamma (B^0 / Bbar^0 -> pi^+ pi^-) approx. 50. Our dynamical model cor…
In the framework of three generations, we consider the CP violation in neutrino oscillation with matter effects. At first, we show that the non-perturbative effects of two small parameters, Δm_{21}^2/Δm_{31}^2 and \sin θ_{13}, become more than 50% in certain ranges of energy and baseline length. This means that the non-perturbative effects should be considered in detailed analysis in the long baseline experiments. Next, we propose a method to include these effects in approximate formulas for oscillation probabilities. Assuming the two natural conditions, θ_{23}=45^\circ and the fact that the m…
The rare decay B^+ \to D_s^+ \bar K^{*0} can occur only via annihilation diagrams in the Standard Model. We calculate the branching ratio in perturbative QCD approach based on k_T factorization theorem. We found that the branching ratio of this decay is about of order 10^{-8}, which may be sensitive to new physics.
We survey the lepton flavor violation branching ratios Br(mu->e,gamma), Br(tau->mu,gamma), and Br(tau->e,gamma) in mSUGRA for a broad class of lepton mass matrix textures that give nearly tribimaximal lepton mixing. Small neutrino masses are generated by the type-I seesaw mechanism with non-degenerate right-handed neutrino masses. The textures exhibit a hierarchical mass pattern and can be understood from flavor models giving rise to large leptonic mixing. We study the branching ratios for the most general CP-violating forms of the textures. It is demonstrated that the branching ratios can be …
Motivated by the experimental data, we study charmless $B_{u,d,s}\to VT$ ($V$ 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 $B\to ϕ(K_2^{*-}, \bar K_2^{*0})$ which agree well with the observed experimental data, however the branching ratios of $B\to ω(K_2^{*-}, \bar K_2^{*0})$ are hard to be explained, where the polarization fra…
New physics thresholds which can modify the diphoton and dilepton Higgs branching ratios significantly may also provide new sources of CP and lepton flavor violation. We find that limits on electric dipole moments impose strong constraints on any CP-odd contributions to Higgs diphoton decays unless there are degeneracies in the Higgs sector that enhance CP-violating mixing. We exemplify this point in the language of effective operators and in simple UV-complete models with vector-like fermions. In contrast, we find that electric dipole moments and lepton flavor violating observables provide le…
We study lepton flavor violation (LFV) in tau decays induced by heavy Majorana neutrinos within two models: (I) the Standard Model with additional right-handed heavy Majorana neutrinos, i.e., a typical seesaw-type model; (II) the Standard Model with left-handed and right-handed neutral singlets, which are inspired by certain scenarios of SO(10)models and heterotic superstring models with E_6 symmetry. We calculate various LFV branching ratios and a T-odd asymmetry. The seesaw Model I predicts very small branching ratios for LFV processes in most of the parameter space, although in a very restr…
This paper is designed to calculate the branching ratio of four-body decays of $B$ meson with lepton number changed by 2. With the new experimental data limit to lepton-number violation processes, we update the upper limits of mixing parameters between heavy Majorana neutrino and charged leptons. Afterwards, we calculate the branching ratio of $B^0(P)\rightarrow D^{*-}(P_1)\ell^+_1(P_2)\ell^+_2(P_3)M_2^-(P_4)$ using the updated parameters. It is found that the most hopeful decay channel is $B^0(P)\rightarrow D^{*-}(P_1)e^+_1(P_2)e^+_2(P_3)ρ^-(P_4)$ or $B^0(P)\rightarrow D^{*-}(P_1)e(μ)^+_1(P_2…
We study $B\to ππ$ decay with a modified perturbative QCD approach. The branching ratios and $CP$ violation are calculated with the transverse momenta of partons considered. Sudakov factor associated with each meson is included to suppress soft contribution in QCD. With the wave function of $B$ meson obtained in QCD-inspired relativistic potential model being used, the suppression of Sudakov factor to the soft contribution is not effective enough. Soft scale cutoff and soft form factors of $Bπ$ transition and $ππ$ production have to be introduced. The main next-to-leading-order contributions o…
The summary of the results of our next-to-next-to-leading fits of Tevatron experimental data for $xF_3$ structure function of the $νN$ deep-inelastic scattering is given. The special attention is paid to the extraction of twist-4 contributions and demonstration of the interplay between these effects and higher-order perturbative QCD corrections. The factorization and renormalization scale uncertainties of the results obtained are analysed
The title of my talk pointed out central statements: the impact of non-perturbative QCD on {\bf CP} asymmetries in many-body FS in charm \& beauty hadrons. For practical reasons one measures first {\bf CP} violation in two-body final states of heavy flavor hadrons. However, those are small parts of charm hadrons and tiny ones for beauty hadrons; therefore one has to probe {\bf CP} asymmetries in three- \& four-body final states. Thus the transitions to the many-body FS basically give information about the underlying dynamics. The impact of non-perturbative QCD on {\bf CP} asymmetries in many-b…
We consider the one-loop radiative corrections to the light-neutrino mass matrix and their consequences for the predicted branching ratios of the five lepton-flavour-violating decays $\ell_1^- \to \ell_2^- \ell_3^+ \ell_3^-$ in a two-Higgs-doublet model furnished with the type-I seesaw mechanism and soft lepton-flavour violation. We find that the radiative corrections are very significant; they may alter the predicted branching ratios by several orders of magnitude and, in particular, they may help explain why $\mbox{BR}(μ^- \to e^- e^+ e^-)$ is strongly suppressed relative to the branching ra…
We study the first observed charmless $B\to VV$ modes, the $B\toϕK^*$ decays, in perturbative QCD formalism. The obtained branching ratios $B(B\toϕK^*)\sim 15 \times 10^{-6}$ are larger than $\sim 9\times 10^{-6}$ from QCD factorization. The comparison of the predicted magnitudes and phases of the different helicity amplitudes, and branching ratios with experimental data can test the power counting rules, the evaluation of annihilation contributions, and the mechanism of dynamical penguin enhancement in perturbative QCD, respectively.
In this work, we calculated the branching ratios, polarization fractions and CP asymmetry of decay modes $B\toρ(ω)ρ(ω)$ in the Perturbative QCD approach, which is based on $\mathbf{k}_T$ factorization. After calculation, we find the the branching ratios of $B^0 \to ρ^+ ρ^-$, $B^+ \to ρ^+ ρ^0$ and $B^+ \to ρ^+ ω$ are at the order of $10^{-5}$, and their longitudinal polarization fractions are more than 90%. The above results agree with BarBar's measurements. We also predict the branching ratios and polarizations of $B^0 \to ρ^0 ρ^0$, $B^0 \to ρ^0 ω$ and $B^0 \to ωω$, which will be measured in f…
This note emphasizes that due to isospin violation the two central states in the octet mix, and this mixing can be measured in semileptonic decays, in particular with an accurate determination of the sigma plus semileptonic branching ratio.
With the perturbative QCD approach based on $k_T$ factorization, we study the pure annihilation type radiative decays $B^0 \to ϕγ$ and $B^0\to J/ψγ$. We find that the branching ratio of $B^0 \to ϕγ$ is $(2.7^{+0.3+1.2}_{-0.6-0.6})\times10^{-11}$, which is too small to be measured in the current $B$ factories of BaBar and Belle. The branching ratio of $B^0\to J/ψγ$ is $({4.5^{+0.6+0.7}_{-0.5-0.6}})\times10^{-7}$, which is just at the corner of being observable in the $B$ factories. A larger branching ratio $BR(B_s^0 \to J/ψγ) \simeq 5 \times 10^{-6}$ is also predicted. These decay modes will he…
We study the flavor changing neutral current decays of the MSSM Higgs bosons into strange and bottom quarks. We focus on a scenario of minimum flavor violation here, namely only that induced by the CKM matrix. Taking into account constraint from $b\to s γ$, $δρ$ as well as experimental constraints on the MSSM spectrum, we show that the branching ratio of $(Φ\to b\bar{s})$ and $(Φ\to \bar{b}s)$ combined, for $Φ$ being either one of the CP even Higgs states, can reach the order $10^{-4}$-$10^{-3}$ for large $\tanβ$, large $μ$, and large $A_t$. The result illustrates the significance of minimal f…
The transverse momentum of a colour-singlet massive particle in a hadronic collision is built up by two components, the perturbative effect of parton branchings and the nonperturbative effect of primordial kT. In previous studies of transverse momentum spectra for Z0 production at the Tevatron, the best fit to the experimental data are given when the primordial kT is set to a much higher value than what is expected considering the confinement of partons in the proton. We here investigate the possibility that the reason for this is that too few branchings are generated in showers, compared to t…
The neutrino experiment results suggest that the neutrinos have finite masses and the lepton-flavor symmetries are violating in nature. In the supersymmetric models, the charged lepton-flavor violating processes, such as mu -> e gamma and tau -> mu gamma, may have the branching ratios accessible to the future experiments, depending on origins of the neutrino masses and the SUSY breaking. In this paper we discuss the branching ratios in the supergravity scenario using the current solar and atmospheric neutrino experimental data.
A widely adopted theoretical scheme to account for the neutrino oscillation phenomena is the see-saw mechanism together with the ``lopsided'' mass matrices, which is generally realized in the framework of supersymmetric grand unification. We will show that this scheme leads to large lepton flavor violation at low energy if supersymmetry is broken at the GUT or Plank scale. Especially, the branching ratio of $μ\to eγ$ already exceeds the present experimental limit. We then propose a phenomenological model, which can account for the LMA solution to the solar neutrino problem and at the same time…
We calculate the CP averaged branching ratios and CP-violating asymmetries for $B^0 \to ηη, ηη^\prime$ and $η^\prime η^\prime$ decays by employing the perturbative QCD (pQCD) factorization approach. The pQCD predictions for the CP-averaged branching ratios are $Br(B^0 \to ηη) \approx 0.67 \times 10^{-7}$, $Br(B^0 \to ηη^\prime) \approx 0.18 \times 10^{-7}$, and $Br(B^0 \to η^{\prime} η^{\prime}) \approx 0.11 \times 10^{-7}$, which are consistent with currently available experimental upper limits. We also predict large CP-violating asymmetries for the considered three decay modes, which can be …
We critically examine the QCD predictions for the $Q^2$ dependence of the electron-proton deep-inelastic structure function $F_2(x,Q^2)$ in the small $x$ region, which is being probed at HERA. The standard results based on next-to-leading order Altarelli-Parisi evolution are compared with those that follow from the BFKL equation, which corresponds to the resummation of the leading log$(1/x)$ terms. The effects of parton screening are also quantified. The theoretical predictions are confronted with each other, and with existing data from HERA. (3 Postscript figures included).
H.~Yamamoto has proposed employing $B$ mesons produced in conjunction with a single charged pion at an $Υ$ resonance for studies of CP violation in the neutral $B$ meson system at a symmetric $e^+$-$e^-$ collider. The sign of the charged pion would tag the neutral $B$ meson. We estimate this branching ratio, employing the heavy meson chiral effective field theory. We find a negligible branching ratio to $B B^{\pm} π^{\mp}$ at the $Υ$(5S) and a branching ratio of only a few percent at the $Υ$(6S). However, if nonresonant studies of neutral $B$ mesons should prove feasible, Yamamoto's proposal c…
Deviation from the standard model prediction is observed in many semileptonic $B$ decays mediated via $b \to c$ charged current interactions. In particular, current experimental measurements of the ratio of branching ratio $R_D$ and $R_{D^{\ast}}$ in $B \rightarrow D^{(*)}l ν$ decays disagree with standard model expectations at the level of about $4.1σ$. Moreover, recent measurement of the ratio of branching ratio $R_{J/Ψ}$ by LHCb, where $R_{J/Ψ} = \mathcal B(B_c \to J/Ψ\,τν)/\mathcal B(B_c \to J/Ψ\,μν)$, is more than $2σ$ away from the standard model prediction. In this context, we consider …
The approximate symmetry of the strong interactions under isospin transformations is among the most precise tools available to control hadronic matrix elements. It is crucial in extracting fundamental parameters, but also provides avenues for the search of phenomena beyond the Standard Model. The precision of the resulting predictions requires special care when determining the quantities they are to be tested with. Specifically, in the extraction of branching ratios often isospin symmetry is assumed at one point or another implicitly, implying a significant bias for precision analyses. We extr…
We compute B->K eta' branching ratio using perturbative QCD approach. We show that a triangular relation among amplitudes for B^0->K^0 pi^0, B^0->K^0 eta, B^0->K^0 eta' receives large corrections from SU(3) breaking effects. If experimental value will come closer to the lower limit of the present BELLE data there will be a possibility to understand the large branching ratio of B^0->K^0 eta'. Otherwise, we perhaps need to modify our understanding of eta' meson, for example, inclusion of a possible admixture of gluonium state.
The apparent gap between the measured and the expected value for the semileptonic branching ratio of $B$ mesons has become more serious over the last year. This is due to the improved quality of the data and to the increasing maturity of the theoretical treatment of non-perturbative corrections. We discuss various theoretical options to reduce the semileptonic $B$ branching ratio; among the more spectacular resolutions of the apparent puzzle is the possibility of an unorthodox enhancement in non-perturbative corrections or even of an intervention by `New Physics'. Phenomenological implications…
The modified perturbative approach in which transverse degrees of freedom as well as Sudakov suppressions are taken into account, is applied to $B$ decays into two $π$ mesons. The influence of various model parameters (CKM matrix elements, $B$ decay constant, mesonic wave functions) on the results as well as short distance corrections to the weak Hamiltonian are discussed in some detail. The perturbative contributions to the $B$ decays yield branching ratios of the order of $10^{-7}\;-\;10^{-6}$ which values are well below the upper limit for the $\bar{B}^0\toπ^+π^-$ branching ratio as measure…
In the framework of perturbative QCD approach, we calculate the branching ratio and CP asymmetry for $B_{s}^0(\bar{B}_{s}) \to π^{\pm} K^\mp$ and $B_{s}(\bar{B}_{s})\to π^{0}\bar{K}^{0}(K^{0})$ decays. Besides the usual factorizable diagrams, both non-factorizable and annihilation type contributions are taken into account. We find that (a) the branching ratio of $B_{s}^0(\bar{B}_{s}) \to π^{\pm} K^\mp$ is about $(6-10) \times 10^{-6}$; $Br(B_{s}(\bar{B}_{s})\to π^{0}\bar{K}^{0}(K^{0}))$ about $ (1-3) \times 10^{-7}$; and (b) there are large CP asymmetries in the two processes, which can be tes…
We consider explicit and spontaneous CP-violation related to the profile of the two Higgs doublets at the MSSM electroweak phase transition. We find, in accordance with previous results, that in principle spontaneous CP-violation could exist in the MSSM at finite temperatures, but when the constraints from experiment and the strength of the transition are taken into account, the relevant region of the parameter space is rather restricted. Nevertheless, we show that in this small region, perturbative estimates need not be reliable, and non-perturbatively the region might be slightly larger (or …
With the potential prospects of the $Υ(1S)$ data samples at the running LHC and upcoming SuperKEKB, the $Υ(1S)$ ${\to}$ $B_{c}ρ$ weak decays are studied with the pQCD approach. It is found that (1) the lion's share of branching ratio comes from the longitudinal polarization helicity amplitudes; (2) branching ratio for the $Υ(1S)$ ${\to}$ $B_{c}ρ$ decay can reach up to ${\cal O}(10^{-9})$, which might be hopefully measurable.
Semi-inclusive top decays, $t \to q_i \v$, are examined in the framework of the standard model, with $q_i = u {\rm or} c$, $\v$ : vector meson formed by $q_j \qb_j$ ($q_j = d, s, b$). By using a simple model of hadronization, that is $ 0 ł| \qb_j γ^μq_j \r| \v = \mv \fv \evj^μ$, the total branching ratio is expected to be $\br(\tivj) < ({ł| \vij^\ast \vtj \r|}/{ł| \vtb \r|})^2 \times O({10}^{-3})$ depends on the size of the coupling constant $\fv$. On the other hand, the CP asymmetry should be induced only by the long-distance effects of intermediate state $q_k \qb_k$ ($q_k = d, s, b$) that su…
In this paper, we calculate the branching ratios for B^0\to D_s^+π^-, B^+\to D_s^+π^0, B^0\to D_s^{*+}π^- and B^+\to D_s^{*+}π^0 decays in the perturbative QCD factorization approach. We find that the calculated branching ratios of these four decay channels agree well with the measured values and current experimental upper limit. In the numerical calculation, we take the decay constant and the shape parameter of the vector meson D^{*}_s as f_{D^{*}_s}=312 MeV and a_{D^{*}_s}=0.78 respectively, which are larger than those in the previous calculations.
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} π^{\mp} and B^{0}(\bar{B}^{0})-->D^{\pm} π^{\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 γ. 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} π^{\mp} and the CP asymmetry of B^{0}(\bar{B}^{0})--> D^{\pm} π^{\mp} agree well with the experimental data. We also give …
Deviation from the standard model prediction is observed in many semileptonic $B$ decays mediated via $b \to c$ charged current interactions. In particular, current experimental measurements of the ratio of branching ratio $R_D$ and $R_{D^{\ast}}$ in $B \rightarrow D^{(*)}l ν$ decays disagree with standard model expectations at the level of about $4.1σ$. Moreover, recent measurement of the ratio of branching ratio $R_{J/Ψ}$ by LHCb, where $R_{J/Ψ} = \mathcal B(B_c \to J/Ψ\,τν)/\mathcal B(B_c \to J/Ψ\,μν)$, is more than $2σ$ away from the standard model prediction. In this context, we consider …
We compute the branching ratios for mu-> e gamma, tau-> mu gamma and tau -> e gamma in a supersymmetric model invariant under the flavour symmetry group A4 X Z3 X U(1)_{FN}, in which near tri-bimaximal lepton mixing is naturally predicted. At leading order in the small symmetry breaking parameter u, which is of the same order as the reactor mixing angle theta_{13}, we find that the branching ratios generically scale as u^2. Applying the current bound on the branching ratio of mu -> e gamma shows that small values of u or tan(beta) are preferred in the model for mass parameters m_{SUSY} and m_{…
