Search

The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron colliders

Using the next-to-leading-order low-energy effective Hamiltonian, the CP asymmetries for B-c-meson decays into meson pairs are calculated in the spectator approximation. We do not compute the hadronic matrix elements directly; instead, ive use the amplitude ratios to estimate the CP asymmetries. This is quite different from previous treatments in the literature. The values of the momentum squared carried by the virtual particles in timelike penguin diagrams are also carefully discussed. From our calculated results, the best decay modes to observe CP violation in B-c decays would be B-c(-) --> (D) over bar K-*o(*-) (D) over bar(o)K(*-), (D) over bar(*o)K(-), (D) over bar(o)K(-), and B-c(-) --> eta(c)D(-), each of them needs about 10(8) of B-c(+/-) events in experiment.

CP violation in neutral D meson decays to the CP eigenstates and non-CP eigenstates is studied systematically within the framework of the Cabibbo-Kobayashi-Maskawa model. The nonleptonic two-body decay processes and the decay processes with semileptonic tagging are discussed in detail and the upper bounds of the direct and indirect CP violation in these decay processes are obtained. A method to measure the mixing parameter \(\tilde{\epsilon}\) and to separate the direct and indirect CP violation in the decay processes with semileptonic tagging are also discussed.

Using the perturbative QCD method and Chau's six-quark-graph scheme, we report a theoretical calculation of exclusive nonleptonic decays of the B meson into two light pseodoscalar mesons in the context of the low-energy effective Hamiltonian. The contributions from both tree-level and one-loop diagrams are taken into account. Under the approximation of neglecting light quark and light meson masses, we find that (i) within perturbative QCD there is no singularity which exists in the computation of spacelike penguin diagrams when the BSW model is used; (ii) the contributions from spacelike-type ( W-annihilation, W-exchange, spacelike penguin and penguin-annihilation) graphs are strongly suppressed relative to those from timelike-type (external W-emission, internal W-emission and timelike penguin) ones; (iii) our results are well below the experimental upper limits but lower than the BSW ones.

We present a new mechanism for $B^{\pm}\to \eta' K^{\pm}$, and analyze it strictly within perturbative QCD. We find that such a new mechanism may dominate non-leptonic $B$-decays to light mesons. Within a reasonable parameter space, our prediction is in good agreement with the recent CLEO data on $B^{\pm}\to \eta' K^{\pm}$. We conclude that there is no room for an abnormally large \bsg vertex from physics beyond the Standard Model.

Using the next-to-leading order low energy effective Hamiltonian for $|\Delta B|=1$, $\Delta C=\Delta U=0$ transitions, the contributions of electroweak penguin operators in $ B^-(\overline {B_d^0})\rightarrow PP$ and $PV$ decays are estimated in the standard model. We find that, for some channels, the electroweak penguin effects can enhance or reduce the QCD penguin and/or tree level contributions by at least $30\%$, and can even play dominant role.

Using the next-to-leading-order, low-energy effective Hamiltonian for , transitions, the contributions of electroweak penguin operators in charmless decays are estimated in the standard model. We find that, for some channels, the electroweak penguin effects can enhance or reduce the QCD penguin and/or tree-level contributions by at least 20%, and can even play a dominant role in decay widths and CP-asymmetries, but the corrections to the angular distribution are negligible.

We argue that the B-c exclusive nonleptonic decays are perturbatively calculable. Working in a perturbative QCD model of Brodsky et al, we pay attention to the estimate of the partial widths of the modes B-c --> J/Psi pi(+), J/Psi rho(+), etc., which serve to identify B-c mesons and determine the B-c mass and life time. Our estimations are found to be lower than the other predictions. We note that the spectator ansatz might be misleading in dealing with B-c weak decays. So the results will be potentially important at LHC to measure the B-c meson and to test various models of weak decays of heavy mesons.

We study the decay $B_c \rightarrow D_s^* \gamma$. There are two mechanisms contributing to the process. One proceeds through the short distance $b{\rightarrow}s\gamma$ transition and the other occurs through weak annihilation accompanied by a photon emission.The electromagnetic penguin contribution is estimated by perturbative QCD and found to be $4.68\times10^{-18}$ GeV. In particular, we find the contribution of the weak annihilation is $6.25\times10^{-18}GeV$ which is in the same order as that of the electromagnetic penguin. The total decay rate $\Gamma(B_c \rightarrow D_s^* \gamma)$ is predicted to be $1.45\times10^{-17}GeV$ and the branching ratio $Br(B_c \rightarrow D_s^* \gamma)$ is predicted to be $2.98\times 10^{-5}$ for $\tau_{B_c}=1.35ps$. The the decays $B_c \rightarrow D_s^* \gamma$ can be well studied at LHC in the near future.

We make a further study of CP asymmetries in the pure penguin-induced decay modesBu−→K(*)0+K(*)− and\(B_u^ - \to \bar K^{(*)0} + (\pi ^ - ,\rho ^ - ,a_1^ - )\) by using the twoloop renormalization-group-improved effective Hamiltonian and factorization approximation. Different from the previous results obtained without QCD corrections, the CP asymmetries in each of the two groups are enhanced and classified with their respective factorization coefficients. A sum over the pure penguin modes of each group is proposed to obtain an effective branching ratio and aweighted-mean signal of CP violation, which should be statistically significant for experimental observation.

The rare decay B→Kτ+τ− is calculated by applying the heavy meson chiral perturbation theory which is a reliable method in this case. The typical order of magnitude of the branching ratio is 10−7. The inclusive decay rate b→sτ+τ− is also given.

We calculate branching ratios for a number of charmless nonleptonic two-body decays of ${B}_{s}$ mesons using the two-loop renormalization-group-improved effective Hamiltonian and the Bauer-Stech-Wirbel model. The QCD loop-induced (penguin) contributions are taken into account, and the leading $\frac{1}{{N}_{c}}$ approximation is examined in the naive factorization scheme. Our present estimates of branching ratios for those Cabibbo-Kobayashi-Maskawa suppressed channels are quite different from the previous results obtained in the tree-level approximation.

By assuming universal Yukawa interactions, the hierarchical pattern of the lepton masses can be understood within the framework of supersymmetry. In a realistic model with R-parity violation, the lepton spectra are obtained.

CP violation in partial-decay-rate asymmetries are examined for some two-body baryonic decays of $$B_d^0 - \bar B_d^0 $$ system. We discuss two feasible experimental circumstances: the symmetrice + e − collisions (i) on theZ 0 resonance to produce incoherent $$B_d^0 \bar B_d^0 $$ states, and (ii) just above the ϒ(4S) resonance to produceC=even $$B_d^0 \bar B_d^0 $$ states. Using the quark-diagram scheme, we estimate the branching ratios of those decays, and the numbers ofb $$\bar b$$ pairs needed for testing theCP-violating effects for 3σ signature. We find that the promising channels may beB 0 , $$\bar B_d^0 \to p\bar p$$ , $$\Delta ^ + \bar \Delta ^ - $$ , $$p\bar \Delta ^ - $$ , $$\Delta ^ + \bar p$$ , $$n\bar n$$ , $$\Delta ^0 \bar \Delta ^0 $$ , $$n\bar \Delta ^0 $$ , $$\Delta ^0 \bar n$$ , $$\Sigma _c^ + \bar \Sigma _c^ - $$ , $$\Lambda _c^ + \bar \Lambda _c^ - $$ , $$\Sigma _c^ + \bar \Lambda _c^ - $$ , $$\Lambda _c^ + \bar \Sigma _c^ - $$ , $$\Sigma _c^0 \bar \Sigma _c^0 $$ , $$\Xi _c^0 \bar \Xi _c^0 $$ , which should be interesting for experimental observation.

Within the standard model, we elucidate the picture of exclusive hadronic B-meson decays, which occur through both the tree and penguin channels. We emphasize that the weak penguin phase is entangled with the strong one and they can be parted only in special approximation. Ignoring this point will lead to significant missing of direct CP violation in either charged-B or neutral-B decays. The effects of these phases on CP-violating partial rate asymmetries are examined, and the relevant ambiguities in the previous literature are clarified.

We make a further study of the CP -violating asymmetry for the decays B d 0 →D + D − , π + π − , and K + π − , which have both tree-level and penguin amplitudes. We confirm that the final-state phase shifts can lead to significant direct CP violation for these decays, and find that the absorptive part in the penguin amplitude can also lead to direct CP -violating asymmetry for each decay, which is about 5% in the standard model. The numerical predictions of the CP -violating asymmetries are given against final-state phase shifts, and they are quite different from those by Tanimoto et al. [Phys. Rev. D 42 (1990) 252].

The B{sub c}{yields}J/{psi}{pi}, {eta}{sub c}{pi} decays are studied in the scheme of the QCD factorization approach. The branching ratios are calculated with the asymptotic distribution amplitude of the pion. The charm quark mass effect is considered. We find that the mass effect on the branching ratios is small.

CP asymmetries for neutral charmed meson decays to CP eigenstates are carefully studied. The formulas and numerical results are presented. The impact on experiments is briefly discussed., Comment: 7 pages, 1 figure, 1 table, Revtex

Some recent progress in China in the study of charmless B decays with QCD factorization is reviewed. Chirally enhanced power corrections and infrared divergence problem are stressed., Comment: 6 pages, 1 figure, 1 table; one footnote is added; Plenary talk given at the International conference on QCD and hadronic physics, June, 16-20, 2005, Beijing, China

The weak decays of {ital B}{sub {ital s}} mesons are calculated within the framework of heavy quark effective theory (HQET). Accurate measurements of these decays will further verify the validity of HQET in addition to the SU(3)-breaking effect.

By using the new result of τ-mass from Beijing spectrometer and the data of τ → 5πντ from ARGUS, the upper limit of ντ-mass of 30 MeV is obtained at 95% confidence level. The upper limit of the ψτ-mass could be largely reduced if a high resolution detector is used in the improved Beijing electron positron collider, which is under discussion.

In this work, we calculate the branching ratios and CP asymmetries of the decays of $B \to ����$ and $��K$ in the frame of QCD factorization in the heavy quark limit. We also compare the results with the estimates by using conventional factorization and experimental measurements., RevTeX, 14 pages including 5 eps figures

With help of the recent developments in the heavy quarkonium physics, we reexamine the long distance(LD) effects in \Bsee dominantly from the charmonium resonances $J/\Psi$ and $\Psi^{\prime}$ through the decay chains $B\ra X_s J/\Psi (\Psi^{\prime}) \ra X_s e^+ e^-$. We find that the resonance to nonresonance interference are reduced substantially., Comment: Revtex file,11 pages,1 figures,Phys.Lett.B in press

We discuss the nonfactorization effects in $B\to J/\Psi+X_{s}$, which is similar to the nonperturbative effect found by Voloshin in the decay $B\to \gamma +X_{s}$. The QCD sum rule has been used to estimate the hadron matrix elements. We find that the correction from this effect is very large and the large discrepancy between the theory and the experimental data can be reduced considerably., Comment: LaTex, 9 pages, 4 figures. Two references added and typo corrected

We discuss the nonfactorization effects in $B\to J/��+X_{s}$, which is similar to the nonperturbative effect found by Voloshin in the decay $B\to ��+X_{s}$. The QCD sum rule has been used to estimate the hadron matrix elements. We find that the correction from this effect is very large and the large discrepancy between the theory and the experimental data can be reduced considerably., LaTex, 9 pages, 4 figures. Two references added and typo corrected

The space-like penguin contributions were ignored on little ground in many previous studies of nonleptonic B decays and CP violation. Taking the penguin-dominated channels $B^{-} _{u}\rightarrow \bar{K}^{0}\pi$ and $B^{-}_{u}\rightarrow K^{0} K^{-}$ for example, we illustrate the non-negligible effects of the space-like penguin diagrams on CP asymmetries. Some quali- tative remarks are given on the gluonic penguin picture and the direct CP violation in exclusive two-body decays of B mesons., Comment: 10 Latex pages, 2 figures. (Accepted for publication in Physics Letters B)

Some of the nonleptonic decays of B mesons are calculated by applying the model-independent QCD sum rule results of the universal form factors in heavy quark symmetry and the factorization hypothesis. The decay constant of the D(s) meson is extracted to be f(Ds) = (281+/-56) MeV. A test of the factorization hypothesis and some ratios of the branching fractions are discussed.

A careful quark-diagram analysis shows that a number of two-body nonleptonic $B$ decays can occur through the so-called hairpin diagram, a QCD loop-induced graph different from penguin in final-state hadronization of valence quarks. Using the two-loop renormalization-group-improved effective Hamiltonian and the naive factorization approximation, we demonstrate the effect of the hairpin diagram on decay rates and $CP$ asymmetries for a few interesting channels such as $B^{0}_{d},\bar{B}^{0}_{d} \rightarrow \psi K_{S}$ and $B^{\pm}_{u}\rightarrow \phi K^{\pm}$. Branching ratios of some pure hairpin decay modes, e.g., $B^{-}_{u}\rightarrow \phi \pi^{-},\phi \rho^{-}$ and $\bar{B}^{0}_{d}\rightarrow \phi \pi^{0},\phi \rho^{0}, \phi \omega, \phi \eta,$ etc., are estimated to be on the order of $10^{-7}$., Comment: 14 pages (Latex, 2 figures available), BIHEP-TH-93-25 (accepted for publication in Phys. Lett. B)

We propose a method for testing the effect of the higher-twist subprocess q/sub 1/+q-bar/sub 2/..--> pi../sup +/(or ..pi../sup -/)+..gamma.. through measuring a special combination of cross sections in p-bar-p and p-p collisions. The extracted higher-twist contribution depends only on the valence-quark distributions inside the proton and antiproton and so is more reliable.

The partial-decay-rate asymmetries of charged-bottom-meson decays ${B}_{u}^{\ifmmode\pm\else\textpm\fi{}}$,${B}_{c}^{\ifmmode\pm\else\textpm\fi{}}$\ensuremath{\rightarrow}PP and PV are systematically studied and estimated. More attention has been paid to penguin contributions. We find that ${B}_{c}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${\ensuremath{\rho}}^{\mathrm{\ensuremath{-}}}$D${\ifmmode\bar\else\textasciimacron\fi{}}^{0}$,${K}^{0}$${F}^{\mathrm{\ensuremath{-}}}$ and ${\mathit{B}}_{\mathit{u}}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}${\mathit{F}}^{\mathrm{\ensuremath{-}}}$${\mathit{D}}^{0\mathrm{*}}$,${\mathit{F}}^{\mathrm{\ensuremath{-}}\mathrm{*}}$${\mathit{D}}^{0}$ are extremely promising because of their large asymmetry and small number of bb\ifmmode\bar\else\textasciimacron\fi{} pairs needed for testing them.

We apply the quaternionic quantum mechanics model for CP nonconservation, previously developed by Adler for K mesons, to heavy-flavor systems. We show that unlike superweak models, it can accommodate anomalously large ${D}^{0}$-D\ifmmode\bar\else\textasciimacron\fi{} $^{0}$ mixing. On the other hand, in common with superweak models, the quaternionic model predicts zero partial-decay-rate asymmetries for decays of charged B and D mesons, and predicts final-state-independent partial-decay-rate asymmetries for the decays of neutral B and D mesons into CP eigenstates.

A new method for the direct measurement of the quark charge is proposed. Instead of a neutrino beam, an electron, photon, or hadron beam can be used so the statistics is much larger in our method. Examples of $\ensuremath{\gamma}\ensuremath{-}N$ and $e\ensuremath{-}N$ collisions are presented for measuring the $u$- and $d$-quark charge.

All proceedings of this conference can be found at this URL; International audience; We discuss a recent implementation of the two-loop radiative corrections to the Higgs boson masses in three public codes for the calculation of the Minimal Supersymmetric Standard Model. We illustrate the residual theoretical and experimental uncertainties, and phenomenological consequences in representative MSSM scenarios. We discuss, in particular, the resulting most conservative upper bounds on the lighter Higgs boson mass in the general or constrained MSSM upon different assumptions.