Search

We reanalyze the $\Lambda_b\to p$ transition form factors in the perturbative QCD (PQCD) approach by including higher-twist light-cone distribution amplitudes (LCDAs) of a $\Lambda_b$ baryon and a proton. The previous PQCD evaluation performed decades ago with only the leading-twist $\Lambda_b$ baryon and proton LCDAs gave the form factors, which are two orders of magnitude smaller than indicated by experimental data. We find that the twist-4 $\Lambda_b$ baryon LCDAs and the twist-4 and -5 proton LCDAs contribute dominantly, and the enhanced form factors become consistent with those from lattice QCD and other nonperturbative methods. The estimated branching ratios of the semileptonic decays $\Lambda_b\to p\ell\bar{\nu}_\ell$ and the hadronic decay $\Lambda_b\to p\pi$ are also close to the data. It implies that the $b$ quark mass is not really heavy enough, and higher-power contributions play a crucial role, similar to the observation made in analyses of $B$ meson transition form factors. With the formalism established in this work, we are ready to study various exclusive heavy baryon decays systematically in the PQCD approach., Comment: 37 pages, 7 figures, version to be published in Eur.Phys.J.C

After the discovery of the double-charm baryon $\Xi_{cc}^{++}$ by LHCb, one of the most important topics is to search for the bottom-charm baryons which contain a $b$ quark, a $c$ quark and a light quark. In this work, we study the two-body non-leptonic weak decays of a bottom-charm baryon into a spin-$1/2$ bottomed baryon and a light pseudoscalar meson with the short-distance contributions calculated under the factorization hypothesis and the long-distance contributions considering the final-state-interaction effects. The branching fractions of all fifty-seven decay channels are estimated. The results indicate that $\Xi_{bc}^+\to\Xi_b^0\pi^+$, $\Xi_{bc}^{0}\to\Xi_{b}^{-}\pi^+$ and $\Omega_{bc}^0\to\Omega_b^-\pi^+$ decay modes have relatively large decay rates and thus could be used to experimentally search for the bottom-charm baryons. The topological diagrams and the SU(3) symmetry of bottom-charm baryon decays are discussed., Comment: 25 pages, 3 figures, 8 tables. Version for publication in EPJC

The doubly charmed baryon $\Xi_{cc}^{++}$ was recently observed by LHCb via the decay processes of $\Xi_{cc}^{++}\to \Lambda_c^+ K^-\pi^+\pi^+$ and $\Xi_c^+\pi^+$. These discovery channels were successfully predicted in the framework that the short-distance contributions are calculated under the factorization hypothesis and the long-distance contributions are estimated using the rescattering mechanism for the final-state-interaction effects. In this paper, we illustrate the above framework in details by systematic studies on the two-body baryonic decays $\mathcal{B}_{cc}\to\mathcal{B}_{c}P$ involving the doubly charmed baryons $\mathcal{B}_{cc}=(\Xi_{cc}^{++} , \Xi_{cc}^+,\Omega_{cc}^+)$, the singly charmed baryons $\mathcal{B}_{c}=(\mathcal{B}_{\bar{3}}, \mathcal{B}_{6})$ and the light pseudoscalar mesons $P=(\pi,K,\eta_{1,8})$., Comment: 31 pages, 4 figures, 9 tables. Version published in Chinese Physics C

The exotic states $X_{0,1}(2900)$ with the quark flavor of $cs\bar{u}\bar{d}$ are recently observed in the mass spectrum of $D^+K^-$ in $B^-\to D^-D^+K^-$ by the LHCb collaboration. To explore the nature of $X_{0,1}(2900)$, except for analyzing their masses and decay widths as usually did in literatures, the study of their production mechanism in $B$-meson weak decays would provide another important information. The amplitude of $B^-\to D^- X_{0,1}$ is non-factorizable. We consider the final-state-interaction effects and calculate them via the rescattering mechanism. The measured branching fractions of $B^-\to D^- X_{0,1}$ are revealed. It is manifested by ${B}^-\to \Lambda_c^-\Xi_c^{(\prime)0}$ and $\Lambda_b^0\to P_c^+K^-$ that the rescattering mechanism can result in the relatively large branching fractions. The similar processes of $B^-\to \pi^-X_{0,1}$ are also analyzed. The isospins of $X_{0,1}$ can be investigated by $B\to DX_{0,1}^{\pm,0}$ decays., Comment: 12 pages, 10 figures. Version published in EPJC. Additional contributions are added in $B\to \pi X_{0,1}$ in Fig.8. Numerical results of the isospin-partner processes are changed by a factor of 2 in Eqs.(12) and (13)