Radiative Baryonic BB Decays

We study the structure-dependent contributions to the radiative baryonic $B$ decays of $B \to {\bf B}{\bf \bar B'}\gamma$ in the standard model. We show that the decay branching ratios of $Br(B \to {\bf B}{\bf \bar B'}\gamma)$ are $O(10^{-7})$, which are larger than the estimated values of $O(10^{-9})$ induced from inner bremsstrahlung effects of the corresponding two-body modes. In particular, we find that $Br(B^- \to \Lambda \bar p \gamma)$ is around $1 \times 10^{-6}$, which is close to the pole model estimation but smaller than the experimental measurement from BELLE.Comment: 11 pages, 2 figures, Revtex4, new fitting is include

Search for XYZXYZ states in Λb\Lambda_b decays at the LHCb

We consider $X(3872)$ and $Y(4140)$ as the vector tetraquark states of $X_c^0\equiv c\bar c u\bar u(d\bar d)$ and $c\bar c s\bar s$, respectively. By connecting $\Lambda_b\to X_c^0\Lambda$ to $B^-\to X_c^0 K^-$, we predict that the branching ratios of $\Lambda_b\to \Lambda(X(3872)^0\to) J/\psi \pi^+\pi^-$ and $\Lambda_b\to \Lambda(Y(4140)\to) J/\psi \phi$ are $(5.2\pm 1.8)\times 10^{-6}$ and $(4.7\pm 2.6)\times 10^{-6}$, which are accessible to the experiments at the LHCb, respectively. The measurements of these $\Lambda_b$ modes would be the first experimental evidences for the $XYZ$ states in baryonic decays.Comment: 7 pages, 1 figure

Pentaquarks from intrinsic charms in Λb\Lambda_b decays

We study the three-body $\Lambda_b$ decays of $\Lambda_b\to J/\psi pM$ with $M=K^-$ and $\pi^-$. The two new states ${\cal P}_{c1}\equiv {\cal P}_c(4380)^+$ and ${\cal P}_{c2}\equiv {\cal P}_c(4450)^+$ observed recently as the resonances in the $J/\psi p$ invariant mass spectrum of $\Lambda_b\to J/\psi p K^-$ can be identified to consist of five quarks, $uudc\bar c$, being consistent with the existence of the pentaquark states. We argue that, in the doubly charmful $\Lambda_b$ decays of $\Lambda_b\to J/\psi pK^-$ through $b\to c\bar c s$, apart from those through the non-resonant $\Lambda_b\to pK^-$ and resonant $\Lambda_b\to \Lambda^*\to pK^-$ transitions, the third contribution with the non-factorizable effects is not the dominant part for the resonant $\Lambda_b\to K^-{\cal P}_{c1,c2}, {\cal P}_{c1,c2}\to J/\psi p$ processes, such that we propose that the ${\cal P}_{c1,c2}$ productions are mainly from the charmless $\Lambda_b$ decays through $b\to \bar u u s$, in which the $c\bar c$ content in ${\cal P}_{c1,c2}$ arises from the intrinsic charms within the $\Lambda_b$ baryon. We hence predict the observables related to the branching ratios and the direct CP violating asymmetries to be ${\cal B}(\Lambda_b\to \pi^-({\cal P}_{c1,c2}\to) J/\psi p)/{\cal B}(\Lambda_b\to K^-({\cal P}_{c1,c2}\to) J/\psi p)=0.8\pm 0.1$, ${\cal A}_{CP}(\Lambda_b\to \pi^-({\cal P}_{c1,c2}\to)J/\psi p)=(-3.9\pm 0.2)\%$, and ${\cal A}_{CP}(\Lambda_b\to K^-({\cal P}_{c1,c2}\to)J/\psi p)=(5.8\pm 0.2)\%$, which can alleviate the inconsistency between the theoretical expectations from the three contributions in the doubly charmful $\Lambda_b$ decays and the observed data.Comment: 10 pages, 2 figures, revised version accepted by PL

Identifying Glueball at 3.02 GeV in Baryonic BB Decays

We examine the nature of the unknown enhancement around 3 GeV observed by the BABAR collaboration in the $m_{p\bar p}$ spectrum of the $\bar B^0\to p\bar p D^0$ decay. Suspecting that the peak is a resonance, which can be neither identified as a charmonium state, such as $\eta_c$ or $J/\psi$, nor classified as one of the light-flavor mesons, we conclude that it corresponds to a glueball fitted as X(3020) with $(m_X,\;\Gamma_X)=(3020\pm 8,\; 107\pm 30)\;\text{MeV}$, which could be the first glueball state above 3 GeV. This state also appears in the $m_{p\bar p}$ spectrum of the $\bar B^0\to p\bar p D^{*0}$ decay.Comment: 11 pages, 2 figure, title changed, revised version accepted by PL

Determinations of ∣Vcb∣|V_{cb}| and ∣Vub∣|V_{ub}| from baryonic Λb\Lambda_b decays

We extract the Cabibbo-Kobayashi-Maskawa matrix element $V_{cb}$ from the exclusive decays of $\Lambda_b\to \Lambda_c\ell\bar \nu_\ell$ and $\Lambda_b\to \Lambda_c M_{(c)}$ with $M=(\pi^-,K^-)$ and $M_c=(D^-,D^-_s)$, where the branching ratios of $\Lambda_b\to \Lambda M_{(c)}$ measured with high precisions have not been used in the previous studies. Explicitly, we find $|V_{cb}|=(44.0\pm 3.5)\times 10^{-3}$, which agrees with the value of $(42.11\pm 0.74)\times 10^{-3}$ from the inclusive $B\to X_c\ell\bar \nu_\ell$ decays. Furthermore, based on the most recent ratio of $|V_{ub}|/|V_{cb}|$ from the exclusive $\Lambda_b$ decays, we obtain $|V_{ub}|=(4.2\pm 0.4)\times 10^{-3}$, which is close to the value of $(4.49\pm 0.24)\times 10^{-3}$ from the inclusive $B\to X_u\ell\bar \nu_\ell$ decays. We conclude that our determinations of $|V_{cb}|$ and $|V_{ub}|$ from the exclusive $\Lambda_b$ decays favor the inclusive extractions in the $B$ decays.Comment: 8 pages, i figur