The radiative decays B*(D*)→B(D)␥ are investigated in the framework of light-cone QCD sum rules. The transition amplitude and decay rates are estimated. It is shown that our results for the branching ratios of D meson decays are in good agreement with the existing experimental data.
We study the b → sγ decay including the next-to-leading QCD corrections in the two Higgs doublet model with flavour changing neutral currents at the tree level. We find the constraints to the flavour changing parameters of the model, using the experimental results on the branching ratio of B → X s γ decay, provided by the CLEO Collaboration. The restrictions coming from the F = 2 (F = K, D, B) mixing and the ρ parameter.
The Bs→ϕψ decay is modeled through the inclusive b→ sψ decay. Using the vector meson dominance model, the amplitude for the chain process Bs→ϕ;ψ→ϕγ→γγ is estimated and it is found to be at most 4% of the corresponding amplitude from the O7 type LD contribution. The intermediate amplitude for the process Bs→ϕγ is compared with the corresponding one obtained by a different approach based on the interaction of the virtual charm quark loop with soft gluons.7 Both amplitudes are found to agree within 10%. Further the influence on the branching ratio B (Bs→γγ) SD + LD O7 from inclusive b→ sψ is estimated to be less than 1%.
The exclusiveB → πe
AbstractWe calculate the leading logarithmic QCD corrections to the matrix element of the decay b → de + e − in the two Higgs doublet model with tree level flavor changing currents (model III). We continue studying the differential branching ratio and the CP violating asymmetry for the exclusive decays B → πe + e − and B → ρe + e − and analysing the dependencies of these quantities on the selected model III parameters, ξ U,D , including the leading logarithmic QCD corrections. Further, we present the forward-backward asymmetry of dileptons for the decay B → ρe + e − and discuss the dependencies to the model III parameters. We observe that there is a possibility to enhance the branching ratios and suppress the CP violating effects for both decays in the framework of the model III. Therefore, the measurements of these quantities will be an efficient tool to search the new physics beyond the SM. * E-mail address: eiltan@heraklit.physics.metu.edu.tr
We consider the single vector leptoquark ͑LQ͒ production at e ϩ e Ϫ and ␥e colliders for two values of the center-of-mass energy ͱsϭ500 GeV and ͱsϭ1000 GeV, in a model-independent framework. We find that the cross sections for the single gauge and nongauge vector LQ productions are almost equal. The discovery limit for a single vector LQ production is obtained for both cases. It is shown that in e ϩ e Ϫ collisions the single vector LQ production is more favorable than the vector LQ pair production, if the Yukawa coupling constant is ϳ1.
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