Search

We revisit the rare leptonic decay $B_s \to \mu^+ \mu^-$ in the two-Higgs doublet models with a softly broken $Z_2$ symmetry, namely type-I, type-II, type-X and type-Y 2HDMs. We have derived the relevant full one-loop Wilson coefficients of the four 2HDMs from the recent calculation in the aligned two-Higgs doublet model by Li, Lu and Pich, which could be mapped to all the four 2HDMs for both large and small $\tan\beta$. It is found that, a new term associated with the soft $Z_2$ symmetry breaking parameter $M$ can be enhanced by $\tan^2\beta$ in the type-II 2HDM, which has not been considered in the literature. Imposing both theoretical and experimental constraints, we have renewed the bounds on the parameter spaces of the four 2HDMs. Different from our previous paper, however, we find that all the four 2HDMs give sizable and similar contributions to $\overline{\mathcal B}(B_s \to \mu^+ \mu^-)$ within the stringently restricted parameter spaces, but very tiny as regards the mass-eigenstate rate asymmetry $\mathcal A_{\Delta\Gamma}$; this makes it unfeasible to discriminate the four types of 2HDM with the correlations between the observables in $B_s \to \mu^+ \mu^-$ decay., Comment: 27 pages, 2 tables, 4 figures; v2: a brief introduction to 2HDM added, matches published version

In this paper, we perform a complete one-loop computation of the short-distance Wilson coefficients for $B_{s,d}-\bar{B}_{s,d}$ mixings and $B_{s,d}\to\ell^+\ell^-$ decays in the Manohar-Wise model, which extends the SM scalar sector by a colour-octet and weak-doublet scalar. Based on these calculations, combined constraints on the model parameters are derived from the current flavour data, including the $B_{s,d}-{\bar{B}}_{s,d}$ mixings, $B_{s,d}\to\mu^+\mu^-$, $B\to X_s\gamma$, $B\to K^{\ast}\gamma$, $B\to\rho\gamma$, and $Z\to b \bar{b}$ decays. The future sensitivity to the model is also explored in the observables achievable with $50~{\rm fb}^{-1}$ of LHCb and $50~{\rm ab}^{-1}$ of Belle-II data. We find that the Manohar-Wise model could explain the current data, especially when the couplings of the charged colour-octet scalars to quarks are complex, with the resulting $\chi^2_{\rm min}$ being significantly smaller than that of the SM. Finally, we investigate correlations among the two isospin asymmetries $\Delta(K^*\gamma)$ and $\Delta(\rho\gamma)$, as well as the averaged time-integrated branching ratios $\bar{{\mathcal B}}(B_{s,d}\to \mu^+\mu^-)$; some of them are found to be quite strong and could, therefore, provide further insights into the model, once more precise experimental measurements and theoretical predictions for these observables are available in the future., Comment: 52 pages, 17 figures and 2 tables; More discussions and references added, final version appeared in JPG

We study the rare decays $D^+\to \pi^{+}\ell^+\ell^-$, $D^+_s\to K^{+}\ell^+\ell^-$ and $D^0\to \ell^+\ell^-(\ell=e,\mu)$ in the minimal supersymmetic standard model with and without R-parity. Using the strong constraints on relevant supersymmetric parameters from $D^0-\bar{D}^0$ mixing and $K^+\to \pi^+\nu\bar{\nu}$ decay, we examine constrained supersymmetry contributions to relevant branching ratios, direct CP violations and ratios of $D^+_{(s)}\to \pi(K)^{+}\mu^+\mu^-$ and $D^+_{(s)}\to \pi(K)^{+}e^+e^-$ decay rates. We find that both R-parity conserving LR as well as RL mass insertions and R-parity violating squark exchange couplings have huge effects on the direct CP violations of $D^+_{(s)}\to \pi(K)^{+}\ell^+\ell^-$, moreover, the constrained LR and RL mass insertions still have obvious effects on the ratios of $D^+_{(s)}\to \pi(K)^{+}\mu^+\mu^-$ and $D^+_{(s)}\to \pi(K)^{+}e^+e^-$ decay rates. The direct CP asymmetries and the ratios of $D^+_{(s)}\to \pi(K)^{+}\mu^+\mu^-$ and $D^+_{(s)}\to \pi(K)^{+}e^+e^-$ decay rates are very sensitive to both moduli and phases of relevant supersymmetric parameters. In addition, the differential direct CP asymmetries of $D^+_{(s)}\to \pi(K)^{+}\ell^+\ell^-$ are studied in detail., Comment: 18 pages, 9 figures

There are four types of two-Higgs doublet models under a discrete $Z_2$ symmetry imposed to avoid tree-level flavour-changing neutral current, i.e. type-I, type-II, type-X and type-Y models. We investigate the possibility to discriminate the four models in the light of the flavour physics data, including $B_s-\bar B_s$ mixing, $B_{s,d} \to \mu^+ \mu^-$, $B\to \tau\nu$ and $\bar B \to X_s \gamma$ decays, the recent LHC Higgs data, the direct search for charged Higgs at LEP, and the constraints from perturbative unitarity and vacuum stability. After deriving the combined constraints on the Yukawa interaction parameters, we have shown that the correlation between the mass eigenstate rate asymmetry $A_{\Delta\Gamma}$ of $B_{s} \to \mu^+ \mu^-$ and the ratio $R={\cal B}(B_{s} \to \mu^+ \mu^-)_{exp}/ {\cal B}(B_{s} \to \mu^+ \mu^-)_{SM}$ could be sensitive probe to discriminate the four models with future precise measurements of the observables in the $B_{s} \to \mu^+ \mu^-$ decay at LHCb., Comment: 29 pages, 4 tables, 11 figures. v3: minor corrections included, matches published version in EPJC

Motivated by the latest improved measurements of B-meson decays, we make a comprehensive analysis of the impact of a family non-universal $Z^{\prime}$ boson on $B_s-\bar{B}_s$ mixing and two-body hadronic B-meson decays, all being characterized by the quark-level $b\to s$ transition. Explicitly 22 decay modes and the related 52 observables are considered, and some interesting correlations between them are also carefully examined. Firstly, the allowed oases of $b-s-Z^{\prime}$ coupling parameters $|B^{L,R}_{sb}|$ and $\phi^{L,R}_s$ are extracted from $B_s-\bar{B}_s$ mixing. Then, in the "SM limit"~({\it i.e.,} no new types of $Z^{\prime}$-induced four-quark operators arise compared to the SM case), we study the $Z^{\prime}$ effects on $B\to\pi K$, $\pi K^{\ast}$ and $\rho K$ decays. It is found that a new weak phase $\phi^{L}_s\sim -90^{\circ}$ is crucial for resolving the observed "$\pi K$ CP puzzle" and the allowed oases of the other $Z^{\prime}$ coupling parameters are also strongly restricted. Moreover, the $Z^{\prime}$ effects on $\bar{B}_s\to K K$, $K K^{\ast}$ and $\pi^0 \phi$ decays, being induced by the same quark-level $b\to s q\bar{q}~(q=u,d)$ transitions, are also investigated. Especially, it is found that the decay $\bar{B}_s \to \pi^0 \phi$, once measured, would play a key role in revealing the observed "$\pi K$ CP puzzle" and probing possible new physics hints. Finally, to check the non-universality of $Z^{\prime}$ couplings to light-quark pairs, we have studied the $B\to \phi K$ decays in detail and found that the left-handed $s-s-Z^{\prime}$ coupling is different from the $d-d-Z^{\prime}$ one, which is due to the large $A_{CP}^{dir}(B^-\to\phi K^-)$ reported by the BaBar collaboration., Comment: 38 pages, 11 figures; To appear in JPG

In the "Higgs basis" for a generic 2HDM, only one doublet gets a nonzero vacuum expectation value and, under the criterion of minimal flavour violation, the other one is fixed to be either colour-singlet or colour-octet, referred respectively as the type-III and the type-C model. Both of them can naturally avoid large FCNC transitions and provide very interesting phenomena in some low-energy processes. In this paper, we study their effects on exclusive radiative B-meson decays due to the exchange of colourless or coloured charged Higgs. It is found that, while constraints from the branching ratios are slightly weaker than the ones from the inclusive $B\to X_{s} \gamma$ decay, the isospin asymmetries in exclusive decays provide very complementary bounds on the model parameters. As the two models predict similar corrections to the dipole coefficient $C_7^{\rm eff}$ whereas similar magnitudes but with opposite signs to $C_8^{\rm eff}$, the branching ratios cannot discriminate the two models, and we have to resort to the direct CP and isospin asymmetries of $b\to s$ processes, which are more sensitive to $C_8^{\rm eff}$. Due to the CKM factors $|\lambda_u^{(d)}|\sim|\lambda_t^{(d)}|$, the terms proportional to $\lambda_u^{(d)}$ make the observables of $b\to d$ processes exhibit a different dependence on the possible new physics phase. In addition, correlations between the various observables in the exclusive $B\to V\gamma$ and the inclusive $B\to X_{s,d}\gamma$ decays are investigated, which could provide further insights into the models with more precise experimental measurements and theoretical predictions for these decays., Comment: 38 pages, 9 figures, 3 tables; more references and discussions added, matches version published in PRD

Large CP violation is an interesting phenomenon both theoretically and experimentally. Last year, LHCb Collaboration found in some three-body decays of bottom mesons that large CP violations appear in regions of the Dalitz plots that are not dominated by contributions from narrow resonances. In this paper, we present a mechanism which can induce such kind of large CP violations. In this mechanism, large localized CP asymmetries in phase space can be induced by the interference of two intermediate resonances with different spins. We also apply this mechanism to the decay channel $B^\pm\to K^\pm \pi^+\pi^-$., Comment: 11 pages, 1 figure

Recently, the large CP asymmetries in $B^\pm\to\pi^\pm\pi^+\pi^-$ decays were found by the LHCb Collaboration to localize in the region $m_{\pi^+\pi^-}^2<0.4 \text{GeV}^2$. We find such large localized CP asymmetries may be due to the interference between a light scalar and $\rho^0(770)$ intermediate resonances. Consequently, we argue that the distribution of CP asymmetries in the Dalitz plots of three-body B decays could be very helpful for identifying the presence of the scalar resonance., Comment: 5 pages, 1 figure, 1 table, to be published on Physical Review D

We calculate the branching ratio of a bottom hadron decaying into a charmed hadron and a charged $\rho$ meson within the QCD factorization approach. We consider the effect of the finite width correction of the $\rho$ meson. Our numerical calculation shows an obvious correction because of this effect. We find that the finite width effect of the $\rho$ meson reduces the branching ratios by about 9% to 11% for bottom meson decay channels: $B^+\to\bar{D^0}\rho^+$, $B^0\to D^-\rho^+$, and $B^0_s\to D^-_s\rho^+$, and increases the branching ratio by about 10% for $\Lambda_b^0\to\Lambda_c^+\rho^-$., Comment: 12 pages

In this paper, we analyze the possible anomalous $tcZ$ coupling effects in the $b \to s $ mediated decays $\bar B \to \bar K^* \mu^+ \mu^-$ and $B_s \to \mu^+ \mu^-$. After exploiting the available experimental data, the combined constraints on the anomalous coupling $X_{ct}^L$ are derived. It is found that, the bound on the magnitude $|X_{ct}^L|$ is dominated by the branching ratios of these two decays. Furthermore, one sign-flipped solution is excluded by the longitudinal fraction of $\bar B \to \bar K^* \mu^+ \mu^-$ at the low dilepton mass region. After considering the combined constraints, for general complex coupling $X_{ct}^L$, the predicted upper bound on $\mathcal B (t \to cZ)$ are compatible with that from the recent CMS direct search. In particular, for the case of real coupling $X_{ct}^L$, the upper bound reads $\mathcal B (t \to cZ)<1.0\times 10^{-4}$, which is much lower than the current CMS bound but still accessible at the LHC. With improved measurements at the LHC, the colser correlations between the $t \to cZ$ and $b \to s$ mediated (semi-) leptonic decays are expected in the near future., Comment: 23 pages, 9 figures, 2 tables. v3: effects due to the width difference \Delta\Gamma_s added, numerical results and figure.3 and 4 slightly changed, main conclusions of the paper remain the same, matches published version in JHEP

Motivated by the recent measurements of non-leptonic $\bar{B}_s^0$ decays by CDF and LHCb collaborations, especially the large ${\cal B}(\bar{B}_s^0\to\pi^+\pi^-)$, we revisit the hard spectator and annihilation corrections in $\bar{B}_s^0$ decays within QCD factorization approach with two schemes for the possible parameters for the known end-point divergence appeared in the estimation of the hard spectator and annihilation diagrams. The first one is to conservatively estimate the possible contributions by parameterization (scheme I); another one uses an infrared finite gluon propagator (scheme II) to regulate the end-point singularity. In scheme I, with the constraints from the measured $\bar{B}_s^0\to PP (VV)$ decays, two (four) restricted solutions of the parameters spaces are found. In scheme II, we find that most of the theoretical predictions agree well with the experimental data with single parameter $m_{g}\sim 0.5{\rm GeV}$. However, within both schemes, ${\cal B}(\bar{B}_s^0\to\phi\phi)$ are always much larger than ${\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ in contrast to the experimental results ${\cal B}(\bar{B}_s^0\to\phi\phi)\simeq{\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$. It is noted that the pattern ${\cal B}(\bar{B}_s^0\to\phi\phi)>{\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ also persists in other theoretical framework, thus the present experimental result ${\cal B}(\bar{B}_s^0\to\phi\phi) \simeq {\cal B}(\bar{B}_s^0\to K^{\ast 0}\bar{K}^{\ast 0})$ rises a challenge to theoretical approaches for B non-leptonic decays. Further refined measurements and theoretical studies are called for to resolve such a possible anomaly., Comment: 25pages, 6 figures; minor typos corrected; version to appear in Phys. Rev. D

The rare decays B_s -> \mu^+\mu^- and B -> K^{(*)}\mu^+\mu^- are sensitive to new particles and couplings via their interferences with the standard model contributions. Recently, the upper bound on B(B_s -> \mu^+\mu^-) has been improved significantly by the CMS, LHCb, CDF, and D{\O} experiments. Combining with the measurements of B(B-> K^{(*)}\mu^+\mu^-), we derive constraints on the relevant parameters of minimal supersymmetic standard model with and without R-parity, and examine their contributions to the dimuon forward-backward asymmetry in B-> K^{*}\mu^+\mu^- decay. We find that (i) the contribution of R-parity violating coupling products \lambda^{\prime}_{2i2}\lambda^{\prime*}_{2i3} due to squark exchange is comparable with the theoretical uncertainties in B-> K \mu^+\mu^- decay, but still could be significant in B-> K^{*}\mu^+\mu^- decay and could account for the forward-backward asymmetry in all dimuon invariant mass regions; (ii) the constrained mass insertion (\delta^{u}_{LL})_{23} could have significant contribution to dA_{FB}(B-> K^{*}\mu^+\mu^-)/ds, and such effects are favored by thr recent results of the Belle, CDF, and LHCb experiments., Comment: 20 pages, 9 figures, published version

As a top-factory, the LHC is performing a direct study of top-quark anomalous FCNC couplings, which are, however, correlated closely with the rare B- and K-meson decays. In this paper, we study the effects of anomalous $tqZ$ (with $q=u,c$) couplings in the rare decays $B_{s,d}\to \mu^+\mu^-$, $B\to X_s \nu \bar\nu$, $B\to K^{(*)}\nu \bar\nu$, $K^+\to \pi^+ \nu \bar\nu$, and $K_L\to \pi^0 \nu \bar\nu$. With the up-to-date experimental bounds on the branching ratios of these channels, constraints on the left-handed anomalous couplings $X_{ct}^L$ and $X_{ut}^L$ are derived, respectively. With these low-energy constraints taken into account, we find that, for real couplings $X_{ct}^L$ and $X_{ut}^L$, the indirect upper bounds on $\mathcal B(t\to qZ)$ are much lower than that from the D0 collaboration, but are still compatible with the $5\sigma$ discovery potential of ATLAS with an integrated luminosity of $10 {\rm fb}^{-1}$. With refined measurements to be available at the LHCb, the future super-B factories, the NA62 at CERN, and the KOTO at J-PARC, closer correlations between the $t\to qZ$ and the rare B- and K-meson decays are expected in the near future, which will be helpful for the searches of the top-quark FCNC decays at the LHC., Comment: 25 pages, 18 figures, 4 tables; More references added, version published in JHEP

Motivated by the recently observed anomalous large dimuon charge asymmetry in neutral B decays and the unexpected large CP phase in the mixing-induced CP asymmetry for B_s-->J/\psi\phi decay, we study the effects of the anomalous tensor couplings to pursue possible solution. With the constraints from the obsevables \phi^{J/\psi\phi}_s, a_{sl}^s and \Delta M_s, the parameter spaces are severely restricted. Numerically, we find the anomalies in B_s^0-\bar{B}_s^0 mixing system could be moderated simultaneously by the contributions induced by the color-singlet or color-octet tensor operators with their respective nontrivial new weak phase \phi_{T1}\approx28.0(15.6) degree or \phi_{T8}\approx-62.1(-74.2) degree and relevant strength parameters g_{T1}\approx6.7(8.5)\times10^{-2} or g_{T8}\approx1.9(2.4)\times10^{-2} for the CP-violating phase \phi^{J/\psi\phi}_s=-0.77(+0.29,-0.37)(-2.36(+0.37,-0.29)), respectively., Comment: 14pages, 2 figures, 3tables

The top-quark FCNC processes will be searched for at the CERN LHC, which are correlated with the B-meson decays. In this paper, we study the effects of top-quark anomalous interactions $tq\gamma$ in the exclusive radiative $B\to K^*\gamma$ and $B\to\rho\gamma$ decays. With the current experimental data of the branching ratios, the direct CP and the isospin asymmetries, bounds on the coupling $\kappa_{tcR}^{\gamma}$ from $B\to K^*\gamma$ and $\kappa_{tuR}^{\gamma}$ from $B\to \rho\gamma$ decays are derived, respectively. The bound on $|\kappa_{tcR}^{\gamma}|$ from ${\mathcal B}(B\to K^{*}\gamma)$ is generally compatible with that from ${\mathcal B}(B\to X_{s}\gamma)$. However, the isospin asymmetry $\Delta(K^{*}\gamma)$ further restrict the phase of $\kappa_{tcR}^{\gamma}$, and the combined bound results in the upper limit, $\mathcal B(t\to c\gamma)<0.21%$, which is lower than the CDF result. For real $\kappa_{tcR}^{\gamma}$, the upper bound on $\mathcal B(t\to c\gamma)$ is about of the same order as the $5\sigma$ discovery potential of ATLAS with an integrated luminosity of $10 {\rm fb}^{-1}$. For $B\to\rho\gamma$ decays, the NP contribution is enhanced by a large CKM factor $|V_{ud}/V_{td}|$, and the constraint on $tu\gamma$ coupling is rather restrictive, $\mathcal B(t\to u\gamma)<1.44\times 10^{-5}$. With refined measurements to be available at the LHCb and the future super-B factories, we can get close correlations between $B\to V \gamma$ and the rare $t\to q\gamma$ decays, which will be studied directly at the LHC ATLAS and CMS., Comment: 25 pages, 15 figures, pdflatex

Recent results from CDF and D{\O} collaborations favor a large CP asymmetry in B_s^0-\bar{B}_s^0 mixing, while the standard model prediction is very small. Such a large phase may imply sizable new physics effects in B_s^0-\bar{B}_s^0 mixing. We compute the gluino-mediated supersymmetry contributions to B_s^0-\bar{B}_s^0 mixing, B_s->K^{(*)-}K^{(*)+} and B->X_s\gamma decays in the frame of the mass insertion approximation. Combining the constraints of \DeltaM_s, \Delta\Gamma_s, \phi^{J/\psi\phi}_s, B(B_s->K^{-}K^{+}) and B(B->X_s \gamma), we find that the effects of the constrained LL and RR insertions in B_s->K^{(*)-}K^{(*)+} decays are small because of the absence of gluino mass enhancement. For m^2_{\tilde{g}}/m^2_{\tilde{q}}=9, the constrained LR insertion can provide sizable contributions to all observables of B_s->K^{(*)-}K^{(*)+} decays except A^{dir}_{CP}(B_s->K^{-}K^{+}), and many observables are sensitive to the modulus and the phase of the LR insertion parameter. Near future experiments at Fermilab Tevatron and CERN LHC-b can test these predictions and shrink/reveal the mass insertion parameter spaces., Comment: 28 pages and 9 figures, published version, 3 figures added

According to heavy-meson chiral perturbation theory, the vector form factor $f_+(q^2)$ of exclusive semi-leptonic decay $B\to \pi \ell \nu$ is closely related, at least in the soft-pion region (i.e., $q^{2} \sim (m_B-m_{\pi})^2$), to the strong coupling $g_{B^* B\pi}$ or the normalized coupling $\hat g$. Combining the precisely measured $q^2$ spectrum of $B\to \pi \ell \nu$ decay by the BaBar and Belle collaborations with several parametrizations of the form factor $f_+(q^2)$, we can extract these couplings from the residue of the form factor at the $B^*$ pole, which relies on an extrapolation of the form factor from the semi-leptonic region to the unphysical point $q^2=m_{B^*}^2$. Comparing the extracted values with the other experimental and theoretical estimates, we can test these various form-factor parametrizations, which differ from each other by the amount of physical information embedded in. It is found that the extracted values based on the BK, BZ and BCL parametrizations are consistent with each other and roughly in agreement with the other theoretical and lattice estimates, while the BGL ansatz, featured by a spurious, unwanted pole at the threshold of the cut, gives a neatly larger value., Comment: 19 pages, no figure. Revised

We revisit $\bar{B}_s\to \pi K$, $\pi K^{\ast}$ and $\rho K$ decays within QCDF formalism and examine the possible effects of a family non-universal $Z^\prime$ boson in these decays. In our evaluations, the strong constraints from $B_d-\bar{B_d}$ mixing on the strength of the left-handed flavor-changing $d-b-Z^{\prime}$ coupling $B_{db}^{L}$ ~($\sim0.2\times10^{-3}$) is also included. Numerically, we find that a new weak phase $\phi^L_d\sim-50^{\circ}$ involved in $B_{db}^{L}$, the negative combination of the $u-u-Z^{\prime}$ and $d-d-Z^{\prime}$ couplings $P_{ud}^{R}$ and/or $D_{ud}^{L}$ with larger absolute value are crucial to improve the agreement of ${\cal B}(\bar{B}_s\to \pi^- K^+)$ between the SM prediction and the experimental measurement. Generally, ${\cal B}(\bar{B}_s\to \pi^- K^+)$ could be reduced by about 18% at most by $Z^{\prime}$ contributions. Moreover, combining with the recent updated measurement on $\beta_s$ by CDF and D0 collaborations, we also find that $Z^{\prime}$ effects in $\bar{B}_s\to \pi^- K^+$ decays are very important for examining whether the CKM-like hierarchy persists in a family non-universal $Z^{\prime}$ coupling matrix., Comment: 20 pages, 4 figures; final version to appear in Nucl. Phys. B

Observation of top quark flavor changing neutral process $t\to c +\gamma$ at the LHC would be the signal of physics beyond the Standard Model. If anomalous $t\to c\gamma$ coupling exists, it will affect the precisely measured $\mathcal{B}(\bar{B} \to X_s \gamma)$. In this paper, we study the effects of a dimension 5 anomalous $ tc \gamma$ operator in $\bar{B} \to X_s \gamma$ decay to derive constraints on its possible strength. It is found that, for real anomalous $t\to c\gamma$ coupling $\kappa_{\rm{tcR}}^\gamma$, the constraints correspond to the upper bounds $\mathcal B (t \to c + \gamma)<6.54 \times 10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma>0$) and $\mathcal B (t \to c + \gamma)<8.52 \times 10^{-5}$ (for $\kappa_{\rm{tcR}}^\gamma<0$), respectively, which are about the same order as the $5\sigma$ discovery potential of ATLAS ($9.4\times 10^{-5}$) and slightly lower than that of CMS ($4.1\times 10^{-4}$) with $10 \ \rm{fb}^{-1}$ integrated luminosity operating at $\sqrt{s} =14$ TeV., Comment: 15 pages, 5 figures. Revised. To appear in PRD

According to the heavy-quark flavour symmetry, the $B\to \pi, K$ transition form factors could be related to the corresponding ones of D-meson decays near the zero recoil point. With the recent precisely measured exclusive semileptonic decays $D \to \pi \ell \nu$ and $D\to K \ell \nu$, we perform a phenomenological study of $B \to \pi, K$ transition form factors based on this symmetry. Using BK, BZ and Series Expansion parameterizations of the form factor slope, we extrapolate $B \to \pi, K$ transition form factors from $q^{2}_{max}$ to $q^{2}=0$. It is found that, although being consistent with each other within error bars, the central values of our results for $B \to \pi, K$ form factors at $q^2=0$, $f_+^{B\to \pi, K}(0)$, are much smaller than predictions of the QCD light-cone sum rules, but are in good agreements with the ones extracted from hadronic B-meson decays within the SCET framework. Moreover, smaller form factors are also favored by the QCD factorization approach for hadronic B-meson decays., Comment: 19 pages, no figure, 5 tables

Motivated by the measured large branching ratio of $\bar{B}^{0}\to\pi^0\pi^0$ (the so-called "$\pi\pi$" puzzle), we investigate the effects of a family non-universal $Z^{\prime}$ model on the tree-dominated $B\to\pi\pi$ decays. We find that the $Z^{\prime}$ coupling parameter $\zeta_{d}^{LR}\sim0.05$ with a nontrivial new weak phase $\phi_d^L\sim-50^{\circ}$, which is relevant to the $Z^{\prime}$ contributions to the QCD penguin sector $\triangle C_5$, is needed to reconcile the observed discrepancy. Combined with the recent fitting results from $B\to\pi K$, $\pi K^{\ast}$ and $\rho K$ decays, the $Z^{\prime}$ parameter spaces are severely reduced but still not excluded entirely, implying that both the "$\pi\pi$" and "$\pi K$" puzzles could be accommodated simultaneously within such a family non-universal $Z^{\prime}$ model., Comment: 28 pages, 4 figures. References and discussions added. To appear in IJMPA

Motivated by the observed forward-backward asymmetry in $B\to K^{\ast} l^+ l^-$ decay, we perform a detailed analysis of this decay mode within a family non-universal $Z^{\prime}$ model. With the related coupling $Z^{\prime}-\bar{s}b$ constrained by $\bar{B}_s-B_s$ mixing, $B\to \pi K$, and $B\to X_s \mu^{+}\mu^{-}$ decays, we look for further constraint on the couplings $Z^{\prime}-\mu^{+}\mu^{-}$ from $A_{FB}(B\to K^{\ast} \mu^{+}\mu^{-})_{0 {\rm GeV}^2\leqslant q^2\leqslant 2 {\rm GeV}^2}$ and get numerically $B_{\mu\mu}^{L,R}\sim{\cal O}(10^{-2})$. Moreover, we find that the relations, $B_{\mu\mu}^{L}

Motivated by the large discrepancy of CP-violating phase in $\bar{B}_s-B_s$ mixing between the experimental data and the Standard Model prediction, we pursue possible solutions within a family non-universal $Z^{\prime}$ model. Within such a specific model, we find that both the $\bar{B}_s-B_s$ mixing anomaly and the well-known "$\pi K$ puzzle" could be moderated simultaneously with a nontrivial new weak phase, $\phi^L_s\sim-72^{\circ}$ (S1) or $-82^{\circ}$ (S2). With the stringently constrained $Z^{\prime}$ coupling $B_{sb}^{L}$, we then study the $Z^{\prime}$ effects on the rare $B\to X_s \mu^+\mu^-$ and $B_s\to \mu^+\mu^-$ decays, which are also induced by the same $b\to s$ transition. The observables of $B\to X_s \mu^+\mu^-$, at both high and low $q^2$ regions, are found to be able to put strong constraints on the $\mu-\mu-Z^{\prime}$ coupling, $B_{\mu\mu}^{L,R}\sim10^{-2}$. It is also shown that the combined constraints from $\bar{B}_s-B_s$ mixing, $B\to \pi K$ and $B\to X_s \mu^+\mu^-$ do not allow a large $Z^{\prime}$ contribution to the pure leptonic $B_s\to\mu^+\mu^-$ decay., Comment: 29 pages, 10 figs and 6 tables. References and discussions added. To appear in JHEP

Motivated by the large difference between the direct CP asymmetries $A_{CP}(B^-\to \pi^0 K^-)$ and $A_{CP}(\bar{B}^{0}\to \pi^{+} K^{-})$, we combine the up-to-date experimental information on $B\to\pi K$, $\pi K^{\ast}$ and $\rho K$ decays to pursue possible solutions with the nonuniversal $Z^{\prime}$ model. Detailed analyses of the relative impacts of different types of couplings are presented in four specific cases. Numerically, we find that the new coupling parameters, $\xi^{LL}$ and $\xi^{LR}$ with a common nontrivial new weak phase $\phi_L\sim-86^{\circ}$, which are relevant to the $Z^{\prime}$ contributions to the electroweak penguin sector $\triangle C_9$ and $\triangle C_7$, are crucial to the observed "$\pi K$ puzzle". Furthermore, they are found to be definitely unequal and opposite in sign. We also find that $A_{CP}(B^-\to \rho^0 K^-)$ can put a strong constraint on the new $Z^{\prime}$ couplings, which implies the $Z^{\prime}$ contributions to the coefficient of QCD penguins operator $O_3$ involving the parameter $\zeta^{LL}$ required., Comment: 27 pages, 6 figures. References and a note added

With the first measurements of the branching ratios and the direct CP asymmetries of $B_s\to K^{-}K^{+}$, $K^{-}\pi^{+}$ decays by the CDF collaboration, we constrain the relevant parameter space of the Minimal Supersymmetric Standard Model with R-parity violation. Using the constrained R-parity violating couplings, we further examine their possible effects in $B_{s}\to K^{-*}\pi^{+}$, $K^{(*)-}\rho^{+}$ and $K^{(*)\pm}K^{(*)\mp}$ decays. We find that some branching ratios and CP asymmetries are very sensitive to the R-parity violating couplings. The direct longitudinal CP asymmetries of tree-dominated process $B_s\to K^{*-}\rho^{+}$ could be enlarged to $\sim 70%$ and the longitudinal polarizations of $B_s\to K^{*-}K^{*+}$, $K^{*-}\rho^{+}$ decays could be suppressed very much by the squark exchange couplings. Near future experiments at CERN LHC can test these predictions and shrink/reveal the parameter spaces of RPV SUSY., Comment: 29 pages, 6 figures, to appear in PRD

Motivated by the possible large direct CP asymmetry of \bar{B}^0_d \to D^+ D^- decay measured by Belle collaboration, we investigate double charm B_{u,d} and B_s decays in the minimal supersymmetric standard model with R-parity violation. We derive the bounds on relevant R-parity violating couplings from the current experimental data, which show quite consistent measurements among relative collaborations. Using the constrained parameter spaces, we explore R-parity violating effects on other observables in these decays, which have not been measured or have not been well measured yet. We find that the R-parity violating effects on the mixing-induced CP asymmetries of \bar{B}^0_d \to D^{(*)+} D^{(*)-} and \bar{B}^0_s \to D^{(*)+}_s D^{(*)-}_s decays could be very large, nevertheless the R-parity violating effects on the direct CP asymmetries could not be large enough to explain the large direct CP violation of \bar{B}^0_d \to D^{+} D^{-} from Belle. Our results could be used to probe R-parity violating effects and will correlate with searches for direct R-parity violating signals in future experiments., Comment: 28 pages and 6 figures, matches published version

We constrain the light CP-odd Higgs $A_{1}^{0}$ in NMSSM via the rare decay $\pi^{0}\to e^{+}e^{-}$. It is shown that the possible $3\sigma$ discrepancy between theoretical predictions and the recent KTeV measurement of ${\cal B}({\pi}^{0}\to e^+ e^-)$ cannot be resolved when the constraints from $\Upsilon\to\gamma A_1^0$, $a_{\mu}$ and $\pi^{0}\to \gamma \gamma$ are combined. Furthermore, the combined constraints also exclude the scenario involving $m_{A_1^0}=214.3$ MeV, which is invoked to explain the anomaly in the $\Sigma^{+}\to p \mu^{+}\mu^{-}$ decay found by the HyperCP Collaboration., Comment: 16 pages, 5 figures. Title changed, pi-A mixing included. Version to appear in PLB

Combining the up-to-date experimental information on $B\to\pi K, \pi K^{\ast}$ and $\rho K$ decays, we revisit the decay rates and CP asymmetries of these decays within the framework of QCD factorization. Using an infrared finite gluon propagator of Cornwall prescription, we find that the time-like annihilation amplitude could contribute a large strong phase, while the space-like hard spectator scattering amplitude is real. Numerically, we find that all the branching ratios and most of the direct CP violations, except $A_{CP}(B^{\pm}\to K^{\pm}\pi^{0})$, agree with the current experimental data with an effective gluon mass $m_g\simeq0.5 {\rm GeV}$. Taking the unmatched difference in direct CP violations between $B\to\pi^{0} K^{\pm}$ and $\pi^{\mp}K^{\pm}$ decays as a hint of new physics, we perform a model-independent analysis of new physics contributions with a set of $\bar{s}(1+\gamma_{5})b\otimes\bar{q}(1+\gamma_{5})q$ (q=u,d) operators. Detail analyses of the relative impacts of the operators are presented in five cases. Fitting the twelve decay modes, parameter spaces are found generally with nontrivial weak phases. Our results may indicate that both strong phase from annihilation amplitude and new weak phase from new physics are needed to resolve the $\pi K$ puzzle. To further test the new physics hypothesis, the mixing-induced CP violations in $B\to\pi^{0}K_{S}$ and $\rho^{0}K_{S}$ are discussed and good agreements with the recent experimental data are found., Comment: Version published in JHEP

We study the rare decays $B^{+}_u\to \pi^{+}\ell^{+}\ell^{-}$, $\rho^{+}\ell^{+}\ell^{-}$ and $B^{0}_d \to \ell^{+} \ell^{-}(\ell=e,\mu)$ in the R-parity violating supersymmetric standard model. From the latest upper limits of $\mathcal{B}(B^+_u\to\pi^+\ell^+\ell^-)$ and $\mathcal{B}(B^0_d\to\ell^+\ell^-)$, we have derived new upper bounds on the relevant R-parity violating couplings products, which are stronger than the existing ones. Using the constrained parameter space, we present the R-parity violating effects on the branching ratios and the forward-backward asymmetries of these decays. We find that $\mathcal{B}(B^0_d\to \ell^+\ell^-)$ and $\mathcal{B}(B^+_u \to\rho^+\ell^+\ell^-)$ could be enhanced several orders by the R-parity violating sneutrino and squark exchanges, respectively. The R-parity violating effects on the dilepton invariant mass spectra of $B^+_u\to \pi^+\ell^+\ell^-$, $\rho^+\ell^+\ell^-$ and the normalized forward-backward asymmetry $\mathcal{A}_{FB}(B^+_u\to\pi^+\ell^+\ell^-)$ and $\mathcal{A}_{FB}(B^+_u \to\rho^+\ell^+\ell^-)$ are studied in detail. Our results could be used to probe the R-parity violating effects and will correlate with searches for the direct R-parity violating signals at the future experiments., Comment: 27 pages, 6 figures

The branching ratios and CP violations of the $B\to D\pi$ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass $\mu_g$ is regarded as a universal scale, it is extracted to be around $\mu_g = 440$ MeV from one of the well-measured $B\to D\pi$ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct $CP$ asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the $B\to D^{\pm}\pi^{\mp}$ decays to be consistent with the experimental data at 1-$\sigma$ level. More precise measurements will be helpful to extract weak angle $2\beta+\gamma$., Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for one of decay channels is improved

We study the decays $B\to K^{(*)}\ell^+\ell^-$ and $B_s\to \ell^+\ell^- (\ell=e,\mu)$ in the minimal supersymmetric standard model with R-parity violation (RPV). From the recent measurements of their branching ratios, we have derived new upper bounds on the relevant RPV coupling products, which are stronger than the existing ones. Using the constrained parameter space, we predict the RPV effects on the forward-backward asymmetries ${\mathcal A}_{FB}(B\to K^{(*)}\ell^+\ell^-)$ and the branching ratios $ {\mathcal B}(B_s\to \ell^{+}\ell^{-}) $. Our results of the forward-backward asymmetries agree with the recent experiment data. It is also found that $\mathcal{B}(B_s\to \ell^+\ell^-)$ could be enhanced several orders by the RPV sneutrino exchange. The RPV effects on the dilepton invariant mass spectra of $B\to K^{(*)}\ell^+\ell^-$ and the normalized ${\mathcal A}_{FB}(B\to K^{(*)}\ell^+\ell^-)$ are studied in detail. Our results could be used to probe RPV effects and will correlate with searches for direct RPV signals at LHC., Comment: 27 pages, 9 figures. Typos corrected and references added

We investigate whether the anomalous tensor operators with the Lorentz structure $\sigma_{\mu\nu} (1+\gamma_{5})\otimes \sigma^{\mu\nu}(1+\gamma_{5})$, which could provide a simple resolution to the polarization anomaly observed in $B\to \phi K^{\ast}$ decays, could also provide a coherent resolution to the large ${\cal B}(B\to \eta K^{\ast})$ and survive bounds from $B\to\eta K$ decays. Parameter spaces satisfying all these experimental data are obtained, and found to be dominated by the color-octet tensor operator contribution. Constraints for the equivalent solution with $(1+\gamma_{5})\otimes(1+\gamma_{5})$ operators are also derived and found to be dominated by the color-singlet one. With the constrained parameter spaces, we finally give predictions for $B_{s}\to \phi \phi$ decay, which could be tested at the Fermilab Tevatron and the LHC-b experiments., Comment: 27 pages, 5 tables and 6 figures. Journal version

The recent measurements of the $B_s$ mass difference $\Delta M_s$ by the CDF and D{\O} collaborations are roughly consistent with the Standard Model predictions, therefore, these measurements will afford an opportunity to constrain new physics scenarios beyond the Standard Model. We consider the impact of the R-parity violating supersymmetry in the $B^0_s-\bar{B}^0_s$ mixing, and use the latest experimental results of $\Delta M_s$ to constrain the size of the R-parity violating tree level couplings in the $B^0_s-\bar{B}^0_s$ mixing. Then, using the constrained R-parity violating parameter space from $\Delta M_s$, we show the R-parity violating effects on the $B_s$ width difference $\Delta\Gamma_{s}$., Comment: 11 pages, 4 figures, to appear in High Energy Physics And Nuclear Physcis

The strong phases and CP violation in the rare $\bar{B}^0\to K^+K^-$, $K^{*\pm}K^\mp$, $K^{*+}K^{*-}$ decays are investigated. As these decays proceed only via annihilation type diagrams in the standard model (SM), a dynamical gluon mass is introduced to avoid the infrared divergence in the soft endpoint regions. The Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators, which leads to a big imaginary part and hence a large strong phase. As a consequence, large CP asymmetries are predicted in those decay modes due to a big interference between the annihilation amplitudes from penguin and tree operators, which may be tested in future more precise experiments., Comment: 21 pages, 6 figures, comments and reference added, published version

We study the branching ratios, the direct CP asymmetries in $B\to K^{(*)}\bar{K}^{(*)}$ decays and the polarization fractions of $B\to K^{*}\bar{K}^{*}$ decays by employing the QCD factorization in the minimal supersymmetric standard model with R-parity violation. We derive the new upper bounds on the relevant R-parity violating couplings from the latest experimental data of $B\to K^{(*)}\bar{K}^{(*)}$, and some of these constraints are stronger than the existing bounds. Using the constrained parameter spaces, we predict the R-parity violating effects on the other quantities in $B\to K^{(*)}\bar{K}^{(*)}$ decays which have not been measured yet. We find that the R-parity violating effects on the branching ratios and the direct $CP$ asymmetries could be large, nevertheless their effects on the longitudinal polarizations of $B\to K^{*}\bar{K}^{*}$ decays are small. Near future experiments can test these predictions and shrink the parameter spaces., Comment: 31 pages with 10 figures

We analyze the $B \to \phi K^{*}$ polarization puzzle in the Minimal Supersymmetric Standard Model (MSSM) including the neutral Higgs boson (NHB) contributions. To calculate the non-factorizable contributions to hadronic matrix elements of operators, we have used the QCD factorization framework to the $\alpha_s $ order. It is shown that the recent experimental results of the polarization fractions in $B\to \phi K^{*}$ decays, which are difficult to be explained in SM, could be explained in MSSM if there are flavor non-diagonal squark mass matrix elements of 2nd and 3rd generations, which also satisfy all relevant constraints from known experiments ($B\to X_s\gamma, B_s\to \mu^+\mu^-, B\to X_s \mu^+\mu^-, B\to X_s g, \Delta M_s$, etc.). We have shown in details that the experimental results can be accommodated with the flavor non-diagonal mass insertion of chirality RL, RL+LR, RR, or LL+ RR when the NHB contributions as well as $\mathcal{O}(\alpha_s)$ corrections of hadronic matrix elements of operators are included. However the branching ratios for the decay are smaller than the experimental measurements., Comment: 15 pages, 5 figures, minor revision and references added

Recent experiments suggest that certain data of $B \to \pi\pi,\pi K$ decays are inconsistent with the standard model expectations. We try to explain the discrepancies with R-parity violating suppersymmetry. By employing the QCD factorization approach, we study these decays in the minimal supersymmetric standard model with R-parity violation. We show that R-parity violation can resolve the discrepancies in both $B \to \pi\pi$ and $B \to \pi K$ decays, and find that in some regions of parameter spaces all these requirements, including the CP averaged branching ratios and the direct CP asymmetries, can be satisfied. Furthermore, we have derived stringent bounds on relevant R-parity violating couplings from the latest experimental data, and some of these constraints are stronger than the existing bounds., Comment: 24 pages, 6 figures and 5 tables. Text revised. Final version to appear in PRD

Motivated by the recent experimental data, we have revisited the $B\to \pi K,\pi \pi$ decays in the framework of QCD factorization, with inclusion of the important strong penguin corrections of order $\alpha_s^2$ induced by $b\to D g^\ast g^\ast$ ($D=d$ or $s$ and $g^\ast$ denotes an off-shell gluon) transitions. We find that these higher order strong penguin contributions can provide $\sim 30%$ enhancement to the penguin-dominated $B\to \pi K$ decay rates, and such an enhancement can improve the consistency between the theoretical predictions and the experimental data significantly, while for the tree-dominated $B\to \pi\pi$ decays, these higher order contributions play only a minor role. When these strong penguin contributions are summed, only a small strong phase remains and the direct CP asymmetries get small corrections. We also find patterns of the ratios between the CP-averaged branching fractions remain nearly unaffected even after including these higher order corrections and the $\pi K$ puzzle still persists. Our results may indicate that to resolve the puzzle one would have to resort to new physics contributions in the electroweak penguin sector as found by Buras {\it et al}., Comment: 43 pages, 19 eps figures. Typos corrected. Final version published in PRD72, 074007(2005)

It is very important to know the strength of annihilation contribution in B charmless nonleptonic decays. $\bar{B}_{s}\to \pi^{+}\pi^{-}$ process could serve a good probe of the strength. We have studied the process in QCD factorization framework. Using a gluon mass scale indicted by the studies of infrared behavior of gluon propagators to avoid enhancements in the soft end point regions, we find that the CP averaged branching ratio is about $1.24\times 10^{-7}$, the direct CP asymmetry $C_{\pi\pi}$ is about -0.05, while the mixing-induced CP asymmetry quite large with the value $S_{\pi\pi}$=0.18. The process could be measured at LHC-b experiments in the near future and would deepen our understanding of dynamics of B charmless decays., Comment: 9 pages, 3 eps figures. To appear in EPJC

The pure penguin process $B\to \phi K^*$ is one of the most important probes of physics beyond the Standard Model. Recently BaBar and Belle have measured the unexpectedly large transverse polarization in the decays $B\to \phi K^*$, which may single out new physics effects beyond the Standard model. We study the possibility that the phenomenon could serve as an important probe of anomalous tensor interactions. We find that a spin flipped tensor interaction with a small strength and a phase could give a possible solution to the polarization puzzle., Comment: Presented at Workshop on B Physics Perspectives at Hadronic Collider, ITP, Beijing, 22-24 November 2004

Recently BABAR and Belle have measured anomalous large transverse polarizations in some pure penguin $B \to VV$ decays, which might be inconsistent with the Standard Model expectations. We try to explore its implications for R-parity violating (RPV) supersymmetry. The QCD factorization approach is employed for the hadronic dynamics of B decays. We find that it is possible to have parameter spaces solving the anomaly. Furthermore, we have derived stringent bounds on relevant RPV couplings from the experimental data, which is useful for further studies of RPV phenomena., Comment: 26 pages, 12 eps figures. Typos corrected and references added. Final version to appear in PRD

With the recent investigations of $g^{\ast}g^{\ast}-\eta^{(\prime)}$ transition form factor and $\eta-\eta^{\prime}$ mixing scheme, we present an updated study of the radiative decays $J/\Psi\to\eta^{(\prime)}\gamma$ in perturbative QCD. The decays are taken as a test ground for the $g^{\ast}g^{\ast}-\eta^{(\prime)}$ transition form factors and the $\eta-\eta^{\prime}$ mixing scheme. The form factors are found to be working for glunic $\eta^{(\prime)}$ productions and the mixing angle is constrained to be $\phi=35.1^{\circ}\pm0.8^{\circ}$., Comment: 10 pages, 2 eps figures