Radiative Leptonic Bc→γℓνˉB_c\to \gamma \ell\bar\nu Decay in Effective Field Theory beyond Leading Order

We study the radiative leptonic $B_c\to \gamma\ell\bar\nu$ decays in the nonrelativistic QCD effective field theory, and consider a fast-moving photon. As a result the interactions with the heavy quarks can be integrated out, and thus we arrive at a factorization formula for the decay amplitude. We calculate not only the relevant short-distance coefficients at leading order and next-to-leading order in $\alpha_s$, but also the nonrelativistic corrections at the order $|\bold{v}|^2$ in our analysis. We find out that the QCD corrections can sizably decrease the branching ratio and thus is of great importance in extracting the long-distance operator matrix elements of $B_c$. For the phenomenological application, we present our results for the photon energy, lepton energy and lepton-neutrino invariant mass distribution.Comment: 24 pages, 5 figures, and 2 tables;new references and a new table added and typos correcte

Estimation of Semileptonic Decays of BcB_c Meson to S-wave Charmonia with NRQCD

We study the semileptonic differential decay rates of $B_c$ meson to S-wave charmonia, $\eta_c$ and $J/\Psi$, at the next-to-leading order accuracy in the framework of NRQCD. In the heavy quark limit, $m_b \to \infty$, we obtain analytically the asymptotic expression for the ratio of NLO form factor to LO form factor. Numerical results show that the convergence of the ratio is perfect. At the maximum recoil region, we analyze the differential decay rates in detail with various input parameters and polarizations of $J/\psi$, which can now be checked in the LHCb experiment. Phenomenologically, the form factors are extrapolated to the minimal recoil region, and then the $B_c$ to charmonium semileptonic decay rates are estimated.Comment: 9 pages, 2 figure and 4 table

Hidden-charm molecular pentaquarks and their charm-strange partners

In the framework of one-pion-exchange (OPE) model, we study the hidden-charm and charm-strange molecular pentaquark systems composed of a heavy baryon $(\Sigma_c, \Sigma_c^*)$ and a vector meson $(\bar{K}^*, \bar{D}^*)$, where the S-D mixing effect is considered in our calculation. Our result shows that the $\Sigma_c\bar{D}^*$ molecular state with $(I=1/2,J^P=3/2^-)$ and the $\Sigma_c^*\bar{D}^*$ molecular state with $(I=1/2,J^P=5/2^-)$ exist in the mass range of the observed $P_c(4380)$ and $P_c(4450)$, respectively. Moreover, we predict two other hidden-charm molecular pentaquarks with configurations $\Sigma_c\bar{D}^*$ $(I=3/2, J^P=1/2^-)$ and $\Sigma_c^*\bar{D}^*$ $(I=3/2, J^P=1/2^-)$ and two charm-strange molecular pentaquarks $P_{cs}(3340)$ and $P_{cs}(3400)$ corresponding to the $\Sigma_c\bar{K}^*$ configuration with $(I=1/2, J^P=3/2^-)$ and the $\Sigma_c^*\bar{K}^*$ configuration with $(I=1/2, J^P=5/2^-)$, respectively. Additionally, we also predict some hidden-bottom $\Sigma_b^{(*)}B^*$ and $B_c$-like $\Sigma_c^{(*)}B^*/\Sigma_b^{(*)}\bar{D}^*$ pentaquarks.Comment: Invited paper for NPA special issue on Recent Progress in Strangeness and Charm Nuclear Physics. 23 pages, 3 figures and 7 tables. The version accepted by NP

Production of Charmed Tetraquarks from BcB_c and BB decays

Hadronic states composed of multi-quark flavors may exist in reality since they are not prohibited by QCD. Compact four quark systems of color singlet are classified as tetraquarks. To understand the properties of these states, more theoretical and experimental efforts are needed. In this work, we study charmed tetraquarks with three light flavors using flavor $SU(3)$ symmetry. States with three different light quarks must be in a ${\bf \bar 6 }$ or a ${\bf 15}$ multiplet. We investigate the production of charmed tetraquarks $X_c$ in $B\to X_c (\overline {X}_c) P$ and $B_c \to X_c P$ decays. Whether the states with three light quarks belong to ${\bf \bar 6}$ or ${\bf 15}$ can be determined by studying various tetraquark $B$ and $B_c$ decays. We demonstrate that the decay amplitudes for these decays can be parametrized by a few irreducible SU(3) invariant amplitudes. We then derive relations for decay widths and CP violating rate difference which can be examined experimentally. Although no experimental measurement is available yet, they might be accessed at the ongoing and forthcoming experiments like the LHCb and Belle-II. Measurements of these observables can not only provide useful information for the study of exotics spectroscopy but are also valuable information towards a better understanding of some non-perturbative aspects of QCD.Comment: 14 page

BcB_c Exclusive Decays to Charmonium and a Light Meson at Next-to-Leading Order Accuracy

In this paper the next-to-leading order (NLO) corrections to $B_c$ meson exclusive decays to S-wave charmonia and light pseudoscalar or vector mesons, i.e. $\pi$, $K$, $\rho$, and $K^*$, are performed within non-relativistic (NR) QCD approach. The non-factorizable contribution is included, which is absent in traditional naive factorization (NF). And the theoretical uncertainties for their branching ratios are reduced compared with that of direct tree level calculation. Numerical results show that NLO QCD corrections markedly enhance the branching ratio with a K factor of 1.75 for $B_{c}^{\pm}\to \eta_{c} \pi^{\pm}$ and 1.31 for $B_{c}^{\pm}\to J/\psi \pi^{\pm}$. In order to investigate the asymptotic behavior, the analytic form is obtained in the heavy quark limit, i.e. $m_b \to \infty$. We note that annihilation topologies contribute trivia in this limit, and the corrections at leading order in $z= m_c/m_b$ expansion come from form factors and hard spectator interactions. At last, some related phenomenologies are also discussed.Comment: 20 pages, 7 figures and 5 table

Predictions of the hidden-charm molecular states with four-quark component

In this work, we study the $T\bar{T}$-type molecular systems systematically via one pion exchange model, where $T$ denotes the narrow $J^P=1^+$ $D_1$ meson or $2^+$ $D_2^*$ meson and $\bar{T}$ is its antiparticle. With the effective potentials, we try to find the bound state solutions of the corresponding systems, which provide crucial information of whether there exist the $T\bar{T}$-type molecular states. According to our analysis, we predict some $T\bar{T}$-type molecular states which may be accessible at future experiments like LHCb and forthcoming BelleII.Comment: 13 pages, 2 figures and 8 tables. Accepted by Eur. Phys. J.