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Register a new userThe $1D$, $2D$ $Xi_{b}$ and $Lambda_{b}$ baryons
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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.
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In this work, the full leading order results of the form factors for $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$ are obtained in QCD sum rules. Contributions from up to dim-5 have been considered. For completeness, we also study the two-point correlation function to obtain the pole residues of $Xi_{Q}$ and $Lambda_{Q}$, and higher accuracy is achieved. For the three-point correlation function, since stable Borel regions can not be found, about $20%$ uncertainties are introduced for the form factors of $Xi_{b}toXi_{c}$ and $Lambda_{b}toLambda_{c}$. Our results for the form factors are consistent with those of the Lattice QCD within errors.
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.
Using the data sample of 711 fb$^{-1}$ of $Upsilon(4S)$ on-resonance data taken by the Belle detector at the KEKB asymmetric-energy electron-positron collider, we present the first measurements of branching fractions of the decays $B^{-} to bar{Lambda}_{c}^{-} Xi_{c}^{0}$, $B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2645)^{0}$, and $B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2790)^{0} $. The signal yields for these decays are extracted from the recoil mass spectrum of the system recoiling against $bar{Lambda}_{c}^{-}$ baryons in selected $B^-$ candidates. The branching fraction of $B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2790)^{0}$ is measured to be $ (1.1 pm 0.4 pm 0.2)times 10^{-3}$, where the first uncertainty is statistical and the second systematic. The 90% credibility level upper limits on ${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}^{0})$ and ${cal B}(B^{-} to bar{Lambda}_{c}^{-} Xi_{c}(2645)^{0})$ are determined to be $6.5times 10^{-4}$ and $7.9times 10^{-4}$, respectively.
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.
A search for previously unobserved decays of beauty baryons to the final states $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of $1.0,mathrm{fb}^{-1}$ of $pp$ collisions. The $Lambda^0_b rightarrow K^0_{mathrm{S}}ppi^-$ decay is observed for the first time with a significance of $8.6,sigma$, and a measurement is made of the $CP$ asymmetry, which is consistent with zero. No significant signals are seen for $Lambda^0_b rightarrow K^0_{mathrm{S}}pK^-$ decays, $Xi^0_b$ decays to both $K^0_{mathrm{S}}ppi^-$ and $K^0_{mathrm{S}}pK^-$ final states, and the $Lambda^0_b rightarrow D^-_s (K^0_{mathrm{S}}K^-)p$ decay, and upper limits on their branching fractions are reported.
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