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Register a new userDiquarks and Lambda_{b}toLambda_c weak decays
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In this work we investigate the weak $Lambda_{b}toLambda_c$ semi-leptonic and non-leptonic decays. The light-front quark model and diquark picture for heavy baryons are adopted to evaluate the $Lambda_{b}toLambda_c$ transition form factors. In the heavy quark limit we study the Isgur-Wise function. By fitting the data of the semi-leptonic process we obtain the mass of the light scalar diquark as 817 MeV. The numerical predictions on the branching ratios of non-leptonic decay modes $Lambda_{b}toLambda_c M$ and various polarization asymmetries are made. A comparison with other approaches is discussed.
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In this work, we study $Lambda_{b}toLambda_{c}$ and $Sigma_{b}toSigma_{c}$ weak decays in the light-front quark model. As is well known, the key point for such calculations is properly evaluating the hadronic transition matrix elements which are dominated by the non-perturbative QCD effect. In our calculation, we employ the light-front quark model and rather than the traditional diquark picture, we account the two spectator light quarks as individual ones. Namely during the transition, they retain their color indices, momenta and spin polarizations unchanged. Definitely, the subsystem composed of the two light quarks is still in a color-anti-triplet and possesses a definite spin, but we do not priori assume the two light quarks to be in a bound system-diquark. Our purpose is probing the diquark picture, via comparing the results with the available data, we test the validity and applicability of the diquark structure which turns a three-body problem into a two-body one, so greatly simplifies the calculation. It is indicated that the two approaches (diquark and a subsystem within which the two light quarks are free) lead to similar numerical results even though the model parameters in the two schemes might deviate slightly. Thus, the diquark approach seems sufficiently reasonable.
Form factors of the rare $Lambda_{b}(Lambda_{b}^*)to Nell^{+}ell^{-}$ decays are calculated in the framework of the light cone QCD sum rules by taking into account of the contributions from the negative parity baryons. Using the obtained results on the form factors, the branching ratios of the considered decays are estimated. The numerical survey for the branching ratios of the $Lambda_b rar Nell^+ell^- $ and $Lambda_b^ast rar Nell^+ell^- $ decays indicate that these transitions could be measurable in LHCb in near future. Comparison of our predictions on the form factors and branching ratios with those existing in the literature is also performed.
Recently, scientists have made great progresses in experiments in searching for the excited states of $Xi_{b}$ and $Lambda_{b}$ baryons such as the $Lambda_{b}(6072)$, $Lambda_{b}(6146)$, $Lambda_{b}(6152)$, $Xi_{b}(6227)$, $Xi_{b}(6100)$, $Xi_{b}(6327)$ and $Xi_{b}(6333)$. Stimulated by these progresses, we give a systematical analysis about the $1D$ and $2D$ states of $Xi_{b}$ and $Lambda_{b}$ baryons with the method of QCD sum rules. By constructing three types of interpolating currents, we calculate the masses and pole residues of these heavy baryons with different excitation modes $(L_{rho},L_{lambda})=(0,2)$, $(2,0)$ and $(1,1)$. As a result, we decode the inner structures of $Lambda_{b}(6146)$, $Lambda_{b}(6152)$, $Xi_{b}(6327)$ and $Xi_{b}(6333)$, and favor assigning these states as the $1D$ baryons with the quantum numbers $(L_{rho},L_{lambda})=(0,2)$ and $frac{3}{2}^{+}$, $frac{5}{2}^{+}$, $frac{3}{2}^{+}$ and $frac{5}{2}^{+}$, respectively. In addition, the predictions about the masses and pole residues of the other $1D$ and $2D$ states of $Xi_{b}$ and $Lambda_{b}$ baryons in this paper are helpful in studying the D-wave bottom baryons in experiments in the future.
The BaBar Collaboration has recently reported branching fractions for semileptonic decays of the $B$ meson into final states with charged and neutral $D_{1}(2420)$ and $D_{2}^{ast}(2460)$, two narrow orbitally excited charmed mesons. We evaluate these branching fractions within the framework of a constituent quark model in two steps, one which involves a semileptonic decay and the other one mediated by a strong process. Our results are in agreement with the experimental data.
Recently, many new excited states of heavy mesons, especially the radially excited states, are discovered. The study of the production processes of these states from the ground b-flavored mesons is of interest. In this paper, we use the improved Bethe-Salpeter method to study the semi-leptonic and non-leptonic decays of $B$, $B_s$, and $B_c$ mesons, where the final states are focused on the radial excited $2S$ and $3S$ states. We find that many channels have branching ratios up to $10^{-4}$, which are within the detection accuracy of current experiments.
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