119180550
Anomalous tqZ coupling effects in rare B- and K-meson decays
A bstractAs 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 Bs,d → μ+μ−, B → Xsν$ \overline \nu $, B → K(*)ν$ \overline \nu $, K+ → π+ν$ \overline \nu $, and KL → π0ν$ \overline \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 B(t → qZ) are much lower than that from the D0 collaboration, but are still compatible with the 5σ discovery potential of ATLAS with an integrated luminosity of 10 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 → 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.
15654773
Probe new physics in leptonic Bc decays at CERN LHC
With respect to large samples of B-c mesons expected to be produced at CERN Large Hadron Collider (LHC) and the large branching ratios Br(B-c --> tau ) and Br(B-c --> mu ), we suggest that, purely leptonic decays could offer an unique probe of the standard model and its extensions such as two Higgs doublet models and models involving supersymmetry, and also the structure of charged weak currents. (C) 1997 Published by Elsevier Science B.V.
124146558
The Annihilation decay B(c)- ---> eta-prime lepton- anti-neutrino
117642602
Revisiting B_s\to\mu^+\mu^- and B\to K^{(*)}\mu^+\mu^- decays in the MSSM with and without R-parity
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.
118222135
QCD Approach to B ---> D pi Decays and CP Violation
The branching ratios and CP violations of the B -> D pi decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams that 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 -> 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 -> D-+/-pi(-/+) decays to be consistent with the experimental data at 1-sigma level. More precise measurements will be helpful to extracting weak angle 2 beta + gamma.
1542336
Extracting Cabibbo-Kobayashi-Maskawa elements in Bc semileptonic decays and heavy quark spin symmetry.
We discuss the extraction of \ensuremath{\Vert}${\mathit{V}}_{\mathit{c}\mathit{s}}$/${\mathit{V}}_{\mathit{c}\mathit{d}}$\ensuremath{\Vert},\ensuremath{\Vert}${\mathit{V}}_{\mathit{c}\mathit{s}}$/${\mathit{V}}_{\mathit{u}\mathit{b}}$\ensuremath{\Vert}, and \ensuremath{\Vert}${\mathit{V}}_{\mathit{c}\mathit{d}}$/${\mathit{V}}_{\mathit{u}\mathit{b}}$\ensuremath{\Vert} from semileptonic ${\mathit{B}}_{\mathit{c}}$ decay in the heavy quark limit. The first corrections to the corresponding ratios of the differential rates of ${\mathit{B}}_{\mathit{c}}$ semileptonic decays are calculated in the zero recoil point within HQET combined with the results of QCD sum rules and chiral perturbation theory, and within the quark model. Special attention is paid to minimize the theoretical uncertainties in the procedure of extracting the ratios. We find many uncertainties can be canceled naturally in the leading level. The ratios also are insensitive to the QCD energy scale \ensuremath{\mu} in the next-to-leading level. The result is potentially important for extracting CKM elements from future measurements at the CERN LHC.
118602451
QCD FACTORIZATION BASED ON SIX-QUARK OPERATOR EFFECTIVE HAMILTONIAN FROM PERTURBATIVE QCD AND CHARMLESS BOTTOM MESON DECAYS B((s)) -> pi pi, pi K, KK
The charmless bottom meson decays are systematically investigated based on an approximate six-quark operator effective Hamiltonian from perturbative QCD. It is shown that within this framework the naive QCD factorization method provides a simple way to evaluate the hadronic matrix elements of two-body mesonic decays. The singularities caused by on mass-shell quark propagator and gluon exchanging interaction are appropriately treated. Such a simple framework allows us to make theoretical predictions for the decay amplitudes with reasonable input parameters. The resulting theoretical predictions for all the branching ratios and CP asymmetries in the charmless B0, B+, Bs → ππ, πK, KK decays are found to be consistent with the current experimental data except for a few decay modes. The observed large branching ratio in B→π0π0 decay remains a puzzle though the predicted branching ratio may be significantly improved by considering the large vertex corrections in the effective Wilson coefficients. More precise measurements of charmless bottom meson decays, especially on CP violations in B → KK and Bs → ππ, πK, KK decay modes, will provide a useful test and guide us to a better understanding on perturbative and nonperturbative QCD.
118727023
Predictive AdS/QCD Model for Mass Spectra of Mesons with Three Flavors
The predictive soft-wall AdS/QCD model with a modified 5D metric at the infrared region is constructed to obtain a nontrivial dilaton solution for three flavor quarks u, d and s. Such a model is shown to incorporate both the chiral symmetry breaking and linear confinement. After considering some high-order terms including the U(1)(L) x U(1)(R) chiral symmetry breaking term, we find that the resulting predictions for the SU(3) octet and singlet resonance states of pseudoscalar, scalar, vector and axial-vector mesons agree well with the experimentally confirmed resonance states. Contributions from the instanton effects given by the determinant term are also discussed. It is observed that the chiral symmetry breaking phenomena of SU(3)(L) x SU(3)(R) and U(1)(L) x U(1)(R) can be well described in this model, while the SU(3) flavor symmetry breaking effect due to quark mass difference in the source term is not enough to explain all of the current experimental data.
118950998
Are the X(4160) and X(3915) charmonium states
Inspired by the newly observed states X(4160) and X(3915), we analyze the mass spectra of these states in different quark models and calculate their strong decay widths by the {sup 3}P{sub 0} model. According to the mass spectra of charmonium states predicted by the potential model, the states {chi}{sub 0}(3{sup 3}P{sub 0}), {chi}{sub 1}(3{sup 3}P{sub 1}), {eta}{sub c2}(2{sup 1}D{sub 2}), {eta}{sub c}(4{sup 1}S{sub 0}) all can be candidates for the X(4160). However, only the decay width of the state {eta}{sub c2}(2{sup 1}D{sub 2}) in our calculation is in good agreement with the data reported by Belle, and the decay of {eta}{sub c2}(2{sup 1}D{sub 2}){yields}DD, which is not seen in experiment, is also forbidden. Therefore, it is reasonable to interpret the charmonium state {eta}{sub c2}(2{sup 1}D{sub 2}) as the state X(4160). For the state X(3915), although the mass of {chi}{sub 0}(2{sup 3}P{sub 0}) is compatible with the experimental value, the calculated strong decay width is much larger than experimental data. Hence, the assignment of X(3915) to the charmonium state {chi}{sub 0}(2{sup 3}P{sub 0}) is disfavored in our calculation.
119272630
Charmless B-s -> PP, PV, VV decays based on the six-quark effective Hamiltonian with strong phase effects II
We provide a systematic study of charmless B-s -> PP, PV, VV decays (P and V denote pseudoscalar and vector mesons, respectively) based on an approximate six-quark operator effective Hamiltonian from QCD. The calculation of the relevant hard-scattering kernels is carried out, the resulting transition form factors are consistent with the results of QCD sum-rule calculations. By taking into account important classes of power corrections involving "chirally enhanced" terms and the vertex corrections as well as weak annihilation contributions with non-trivial strong phase, we present predictions for the branching ratios and CP asymmetries of B-s decays into PP, PV and VV final states, and also for the corresponding polarization observables in VV final states. It is found that the weak annihilation contributions with non-trivial strong phase have remarkable effects on the observables in the color-suppressed and penguin-dominated decay modes. In addition, we discuss the SU(3) flavor symmetry and show that the symmetry relations are generally respected.
122838355
DYNAMICAL STUDY OF HEAVY-BARYON SPECTROSCOPY
The spectroscopy of S-wave heavy-baryons containing one, two or three heavy quarks is investigated in a constituent quark model. We solve the Schrodinger equation for three particles exactly by means of a Gaussian expansion method. The calculated results of heavy-baryon spectra with a single heavy quark are consistent with the experimental data.