We interpret the scalar B Ã s0 ð5725Þ as an S-wave B " K molecular bound state in the Bethe-Salpeter approach. In the ladder and instantaneous approximation, with the kernel induced by and ! exchanges, we establish the Bethe-Salpeter equation for B Ã s0 ð5725Þ. We find that the bound state of B " K can exist. We also calculate the isospin-violating decay width of the process B Ã s0 ð5725Þ ! B s 0 through exchanging K Ã and B Ã mesons including the À 0 mixing effect. We hope that the obtained decay width is instructive for the forthcoming experiment.
We analyze the observed state D Ã s0 ð2317Þ þ in the Bethe-Salpeter approach. Assuming that D Ã s0 ð2317Þ þ is an S-wave DK molecular bound state, we establish the Bethe-Salpeter equation for D Ã s0 ð2317Þ þ . With the kernel induced by and ! exchange diagrams, we solve the Bethe-Salpeter equation numerically and find that the bound state of DK indeed can exist. We also calculate the decay width of the isospin-violating mode D Ã s0 ð2317Þ þ ! D þ s 0 through exchanging vector mesons D Ã and K Ã including the À 0 mixing effect which gives important contribution to the decay width. We find that the decay width is smaller than the resolution of the experimental detector.
We analyze the radiative leptonic Bc decay Bc− → τ−ν̄γ in the Standard Model and the two-Higgs-doublet model using the non-relativistic constituent quark model. The results confirm that this channel is experimentally promising in view of the large number of Bc mesons which are expected to be produced at future hadron facilities. We also find that this decay is sensitive to the parameters of the two-Higgs-doublet model, and it can be tested in future experiments.
We have studied the nonleptonic Λ b → π − (D − s)Λ * c and the semileptonic Λ b →ν l lΛ * c decays, with Λ * c ≡ Λ c (2595), Λ c (2625), from the perspective that the two Λ * c resonances are dynamically generated from the DN, D * N interaction with coupled channels. We have developed a formalism to relate the Λ b → π − DN and Λ b → π − D * N decays. We can evaluate the rates for these transitions, up to a global unknown factor. We find that the ratios of the rates obtained for these reactions are compatible with present experimental data and are very sensitive to the D * N coupling, which becomes essential to obtain agreement with experiment. The results obtained with these reactions give support to the molecular picture for these two Λ * c resonances. Work with other models and checks for further experiments will help us gain further insight on the nature of these resonances, and new experiments producing these two resonances should be encouraged.
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