On the semileptonic decay distributions from the next heavy quark

Motivated by the discovery of λ(9.4), we study the semileptonic decay correlations of the next heavy quark, and their consequences for thee ⁺ e ^? colliding beam and neutrino experiments. A detailed comparison is made with the corresponding correlations from the production and decay of charm and heavy leptons, τ^±. Some tests of the \({\rm B}^0 - \bar {\rm B}^0 \) mixing ( \(B = b\bar q\) withbaQ=?1/3 heavy quark) are suggested fore ⁺ e ^? colliding beam experiments.     

Forward-backward asymmetry in top quark semileptonic decay

The semileptonic decay of the top quark t → bW⁺ → bl⁺ν_l is analyzed in the rest system of the W. The forward-backward asymmetry of the lepton l⁺ with respect to the heavy quark direction is defined and computed. It is argued that this observable will be an ideal tool to study top quark properties at Tevatron and LHC. Higher order QCD corrections are calculated and their structure is elucidated in some detail.     

Rare semileptonic decays of heavy mesons in the heavy quark limit

We study the branching ratios of D+→D0e+ν,DS+→D0e+ν,BS0→B+e-ν,DS+→D+e-e+ and BS0→B0e-e+ rare semileptonic decay processes,which are induced by decays of light quarks,the heavy quarks remain unchanged.The branching ratios of these decay processes are estimated in the heavy quark limit and with SU(3) flavor symmetry.We find that the decay rates are very tiny in the framework of the Standard Model.We also estimate the sensitivities of the measurements of these rare decays at the future experiments,such as BES-Ⅲ,super-B and LHC-b.Observations of these decays may shed some light on new physics beyond the standard model.     

Rare semileptonic decays of heavy mesons in the heavy quark limit

We study the branching ratios of D^＋ → D^0e^＋ν, Ds^＋ → D^0e^＋ν, Bs^0→B^＋e^-^-ν, Ds^＋→D^＋e^-e^＋ and Bs^0→B^0e^-e^＋ rare semileptonic decay processes, which are induced by decays of light quarks, the heavy quarks remain unchanged. The branching ratios of these decay processes are estimated in the heavy quark limit and with SU（3） flavor symmetry. We find that the decay rates are very tiny in the framework of the Standard Model. We also estimate the sensitivities of the measurements of these rare decays at the future experiments, such as BES-Ⅲ, super-B and LHC-b. Observations of these decays may shed some light on new physics beyond the standard model.     

Predictions for semileptonic decay rates of charmed baryons in the quark confinement model

Baryons as relativistic three-quark states are investigated in the quark confinement model (QCM), a relativistic quark model based on some assumptions about hadronization and quark confinement. In the framework of the quark-diquark approximation of the three-quark structure of baryons, the main characteristics of light (noncharmed) baryons are calculated. The obtained results agree with experimental data. Predictions are also given for semileptonic decay of charmed baryons and differential production cross-sections in quasielastic neutrino scattering of charmed baryons.     

A quark model study of semileptonic baryon decays in the electronic decay modes

A relativistic quark model based on Dirac equation with the independent-quark confining potential of the form (1 +γ ⁰)[a ln(r/b)] is used to compute the weak electric and magnetic form factors for semileptonic baryonic decays in the electronic decay modes. The values obtained for (g ₂/g ₁) agree with the non relativistic results and those for (f ₂/f ₁) agree with the MIT bag model values of Donoghue and Holstein. The SU(3) symmetry breaking does not generate appreciable departures in (f ₂/f ₁) values from corresponding Cabibbo values.     

Determination of heavy quark non-perturbative parametersfrom spectral moments in semileptonic B decays

Moments of the hadronic invariant mass and of the lepton energy spectra in semileptonic B decays have been determined with the data recorded by the DELPHI detector at LEP. From measurements of the inclusive b-hadron semileptonic decays, and imposing constraints from other measurements on b- and c-quark masses, the first three moments of the lepton energy distribution and of the hadronic mass distribution, have been used to determine parameters which enter into the extraction of |V_cb| from the measurement of the inclusive b-hadron semileptonic decay width. The values obtained in the kinetic scheme are: and include corrections at order 1/m_b³. Using these results, and present measurements of the inclusive semileptonic decay partial width of b-hadrons at LEP, an accurate determination of |V_cb| is obtained: Received: 26 April 2005, Revised: 16 September 2005, Published online: 16 November 2005     

Static properties and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

We evaluate static properties and semileptonic decays for the ground state of doubly heavy Ξ, Ξ', Ξ ^* and Ω, Ω', Ω ^* baryons. Working in the framework of a nonrelativistic quark model, we solve the three-body problem by means of a variational ansatz made possible by heavy-quark spin symmetry constraints. To check the dependence of our results on the inter-quark interaction we use five different quark-quark potentials that include a confining term plus Coulomb and hyperfine terms coming from one-gluon exchange. Our results for static properties (masses, charge radii and magnetic moments) are, with a few exceptions for the magnetic moments, in good agreement with a previous Faddeev calculation. Our much simpler wave functions are used to evaluate semileptonic decays of doubly heavy Ξ, Ξ'(J = 1/2) and Ω, Ω'(J = 1/2) baryons. Our results for the decay widths are in good agreement with calculations done within a relativistic quark model in the quark-diquark approximation. An erratum to this article is available at .     

Ratios ofB andD meson decay constants with heavy quark symmetry

SU(3) flavor symmetry allows the decay constantsf _{D 1} andf _{D 2} as well asf _{B 1} andf _{B 1} to be equal. But due toSU(3) flavor symmetry breaking the ratiosf _{B 1}/f _{B 2} andf _{D 1}/f _{D 2} are deviated from unity. We have estimated these ratios in the heavy quark effective theory and obtainedf _{B 1}/f _{B 2}=0.93,f _{D 1}/f _{D 2}=0.94 and the double ratio (f _{B 1}/f _{B 2})/(f _{D 1}/f _{D 2})=0.99.     

Heavy meson spectra for heavy quark potential in quantum chromodynamics with dilaton

For heavy meson systems, we study the heavy quark potential, which emerges from the effective dilaton－gluon coupling inspired from the superstring theory. We put emphasis on the new confinement generating mechanism of this potential through the investigation of the spin-averaged energy levels of the heavy meson systems. By using a unified approach to the solutions of the Schr?dinger and the spinless Salpeter equations, we can examine in a realistic way the effects of using a relativistic kinetic energy. The obtained results agree favourably with other predictions, and the relativistic equation can better account for the observed energy levels.