The detection of radially excited heavy meson \\states in recent years and measurement of heavy meson decays, particularly $B_c^+\to J/ψD_s^+$ and $B_c^+\to J/ψD_s^{*+}$, by the LHCb and ATLAS Collaborations, have aroused a lot of theoretical interest in the nonleptonic decays of $b$-flavored mesons. In this paper, we study the exclusive two-body nonleptonic $\bar{B}^0$, $\bar{B_s^0}$, $B^-$ and $B_c^-$-meson decays to two vector meson ($V_1(nS)V_2$) states. Assuming the factorization hypothesis, we calculate the weak-decay form factors from the overlapping integrals of meson wave functions, in the framework of the relativistic independent quark (RIQ) model. We find a few dominant decay modes: $B^-\to D^{*0}ρ^-$, $\bar{B^0}\to D^{*+}ρ^-$, $\bar{B_s^0}\to D_s^{*+}ρ^-$, $B^-\to J/ψK^{*-}$ and $B_c^-\to J/ψD_s^{*-}$ with predicted branching fractions of 1.54, 1.42, 1.17, 0.53 and 0.52 (in $\%$), which are experimentally accessible. The predicted branching fractions for corresponding decay modes to excited ($2S$) states, obtained in the order ${\cal O }(10^{-3}-10^{-4})$ lie within the detection accuracy of the current experiments at LHCb and Tevatron. The sizeable $CP$-odd fractions predicted for $B_c^-$-meson decay to two charmful states: $D^{*0}D^{*-}_{(s)}$ and $\bar{D}^{*0}D^{*-}_{(s)}$ indicate significant $CP$-violation hinting at the so-called new physics beyond the standard model.
We discuss the validity of factorization for exclusive two-body B to charmonium transitions. In particular, we consider the role of non factorizable corrections in selected two-body modes.
This talk consists of two parts. We first present a light-cone QCD sum rule computation of the $B_s\to f_0(980)$ form factors which are necessary inputs in semileptonic and nonleptonic $B_s$ decays into $f_0(980)$. Then we analyze nonleptonic $B_s$ decays into a charmonium state and a light meson, which are potentially useful to access the $B_s$-${\bar B}_s$ mixing phase $β_s$. We explore the experimental feasibility of measuring these various channels, paying attention to different determinations of $β_s$ in view of the hints of new physics recently emerged in the $B_s$ sector.
We have computed branching ratios of two-body nonleptonic B_c \to X_{c\bar{c}}M decays, where X_{c\bar{c}} is the radially excited charmonium η_c(2S) or ψ(2S) meson, and M is a pseudoscalar (P) or a vector (V) or an axial-vector (A(^3P_1)) meson. We have assumed factorization hypothesis and calculated the form factors in the nonrelativistic ISGW2 quark model. We have found that some of these decays have branching ratios of the order of 10^{-3} - 10^{-4}.
We study the exclusive two-body nonleptonic $B_c\to X_{c\bar{c}}M$ decays, where $X_{c\bar{c}}$ is either a ground(1S) or a radially excited (2S or 3S) charmonium and $M$ is a pseudoscalar $(P)$ or a vector $(V)$ meson. We consider here three categories of decays: $B_c \to PP, PV, VP$ decays within the framework of relativistic independent quark(RIQ) model based on a flavor-independent interaction potential in scalar-vector harmonic form. Using the factorization approximation, we calculate the weak form factors from the overlapping integrals of meson wave functions obtained in the RIQ model an…
We analyze nonleptonic $B_s$ decays to a charmonium state and a light meson, induced by the $b \to c {\bar c}s$ transition, which are useful to access the $B_s$-${\bar B}_s$ mixing phase $β_s$. We use generalized factorization and $SU(3)_F$ symmetry to relate such modes to correspondent $B$ decay channels. We discuss the feasibility of the measurements in the various channels, stressing the importance of comparing different determinations of $β_s$ in view of the hints of new physics effects (NP) recently emerged in the $B_s$ sector. Finally, adopting a general parametrization of NP contributio…
The form factors of weak decays of the B_c meson to orbitally excited charmonium, D, B_s and B mesons are calculated in the framework of the QCD-motivated relativistic quark model based on the quasipotential approach. Relativistic effects are systematically taken into account. The form factor dependence on the momentum transfer is reliably determined in the whole kinematical range. The form factors are expressed trough the overlap integrals of the meson wave functions which are known from the previous mass spectra calculations within the same model. On this basis semileptonic and nonleptonic B…
In this work, we present an analysis of the nonleptonic charmonium modes $B_s^0 \to J / ψf_2^\prime(1525)$ and $B_s^0 \to J/ψK^+K^-$. Within the framework of the factorization approach and using the perturbative QCD for the evaluation of the relevant form factors, we find a branching fraction for the two-body channel of BR$(B_s^{0} \to J/ψf_2^{\prime}(1525)) = (1.6 {}^{+0.9}_{-0.7})\times 10^{-4}$ which is in agreement with the experimental values reported by the LHCb and Belle Collaborations. The associated polarization fractions to this vector-tensor mode are also presented. On the other han…
We re-calculate the exclusive semileptonic and nonleptonic decays of $B_c$ meson to a $P$-wave charmonium in terms of the improved Bethe-Salpeter (B-S) approach, which is developed recently. Here the widths for the exclusive semileptonic and nonleptonic decays, the form factors, and the charged lepton spectrums for the semileptonic decays are precisely calculated. To test the concerned approach by comparing with experimental measurements when the experimental data are available, and to have comparisons with the other approaches the results obtained by the approach and those by some approaches …
Semileptonic and nonleptonic decays of the B_c meson to charmonium and D mesons are studied in the framework of the relativistic quark model. The decay form factors are explicitly expressed through the overlap integrals of the meson wave functions in the whole accessible kinematical range. The relativistic meson wave functions are used for the calculation of the decay rates. The obtained results are compared with the predictions of other approaches.
Nonleptonic $B$ to charmonium decays generally deviate from the factorization predictions. We study rescattering effects mediated by intermediate charmed mesons in this class of decay modes and, in particular, we consider $B^- \to K^- h_c$ with $h_c$ the $J^{PC}=1^{+-}$ $\bar c c$ meson, relating this mode to $B^- \to K^- χ_{c0}$. We find ${\cal B}(B^- \to K^- h_c)$ large enough to be measured at the $B$ factories, hence this process could be used to study the poorly known $h_c$.
Recent data on inclusive B decays into charmonium states taken by the CLEO collaboration suggest that a sizeable fraction of the nonleptonic decays may consist of the $J/ψΛ\overline p$ three body final state, corresponding to a distinct enhancement in the inclusive $J/ψ$ momentum distribution. The kinematical boundary of this structure corresponds to the case where the $J/ψ$ recoils nearly monoenergetically in the B rest system against a partner having mass of $\simeq$ 2 GeV. This may allow the observation of a $Λ-\overline p $ bound state near or just below threshold; i.e., strange baryonium,…
The decay $Ξ^-_b \to π^- Λ_b$ has recently been observed by the LHCb Collaboration at CERN. In contrast to most weak decays of $b$-flavored baryons, this process involves the decay of the strange quark in $Ξ_b$, and thus has features in common with nonleptonic weak decays of hyperons. Thanks to the expected pure S-wave nature of the decay in question in the heavy $b$ quark limit, we find that its amplitude may be related to those for S-wave nonleptonic decays of $Λ$, $Σ$, and $Ξ$ in a picture inspired by duality. The calculated branching fraction ${\cal B}(Ξ^-_b \to π^- Λ_b) = (6.3 \pm 4.2) \t…
Nonleptonic $B$ to charmonium decays generally show deviations from the factorization predictions. For example, the mode $B^- \to K^- χ_{c0}$ has been experimentally observed with sizeable branching fraction while its factorized amplitude vanishes. We investigate the role of rescattering effects mediated by intermediate charmed meson production in this class of decay modes, and consider $B^- \to K^- h_c$ with $h_c$ the $J^{PC}=1^{+-}$ $\bar c c$ meson. Using an effective lagrangian describing interactions of pairs of heavy-light $Q{\bar q}$ mesons with a quarkonium state, we relate this mode t…
We review how quark models are able to describe the phenomenology of the charm meson sector. The spectroscopy and decays of charmonium and open charm mesons are described in a particular quark model and compared with the data and the results of other existing models in the literature. A quite reasonable global description of the heavy meson spectra is reached. A new assignment of the $ψ(4415)$ resonance as a 3D state leaving aside the 4S state to the X(4360) is tested through the analysis of the resonance structure in $e^{+}e^{-}$ exclusive reactions around the $ψ(4415)$ energy region. We make…
The semileptonic decays $B_c^+\rightarrow P(V) +\ell^++\barν_\ell$ and the nonleptonic decays $B_c^+\rightarrow P(V)+L$, where $P(V)$ denotes a pseudoscalar (vector) charmonium or ($\bar{b}s$)-meson, and $L$ denotes a light meson, are studied in the framework of improved instantaneous Bethe-Salpeter (BS) equation and the Mandelstam formula. The numerical results (width and branching ratio of the decays) are presented in tables, and in order to compare conveniently, those obtained by other approaches are also put in the relevant tables. Based on the fact that the ratio $\frac{\mathcal{BR}(B_c^+…
The semileptonic decays, $B_{c}{\longrightarrow}{χ_c}(h_c)+{\ell}+{ν}_{\ell}$, and the two-body nonleptonic decays, $B_{c}{\longrightarrow}{χ_c}(h_c)+h$, (here $χ_c$ and $h_c$ denote $(c\bar c[^3P_J])$ and $(c\bar c[^1P_1])$ respectively, and $h$ indicates a meson) were computed. All of the form factors appearing in the relevant weak-current matrix elements with $B_c$ as its initial state and a $P$-wave charmonium state as its final state for the decays were precisely formulated in terms of two independent overlapping-integrations of the wave-functions of $B_c$ and the $P$-wave charmonium and …
We make a systematic investigation on the two-body nonleptonic decays $B_c\rightarrow J/Ψ(η_c),M$ by employing the perturbative QCD approach based on $k_T$ factorization, where $M$ is a light pseudoscalar or vector or a heavy charmed meson. We predict the branching ratios and direct CP asymmetries of these $B_c$ decays and also the transverse polarization fractions of $B_c\rightarrow J/ΨV,J/ψD^{*}_{(s)}$ decays. It is found that these decays have a large branching ratios of the order of $10^{-4} - 10^{-2}$ and could be measured by the future LHC-b experiment. Our predictions for the ratios of …
Motivated by the powerful capability of measurement for the $b$-flavored hadron rare decays at LHC and SuperKEKB/Belle-II, the nonleptonic $\bar{B}^{\ast}$ ${\to}$ $D\bar{D}^{\ast}$, $D{ρ^-}$, $DK^{\ast-}$, $πD^{\ast}$ and $KD^{\ast}$ weak decays are studied in detail. With the amplitudes calculated with factorization approach and the form factors of $B^{\ast}$ transition into pseudoscalar meson evaluated with the BSW model, branching fractions and polarization fractions are firstly presented. Numerically, the CKM-favored $\bar{B}_{q}^{\ast}$ ${\to}$ $D_{q}D_{s}^{{\ast}-}$ and $D_{q}ρ^{-}$ dec…
We explore the application and usefulness of the heavy quark symmetry to describe the weak decays of hadrons (mesons and baryons) containing two heavy quarks. Firstly, we address the internal dynamics of a heavy-heavy bound system with the help of estimates based on potential models, showing an approximate spin symmetry in the preasymptotic quark mass region including charmonium, bottonium and $B_c$ meson states. However, no asymptotic spin symmetry should hold in the infinite quark mass limit in contrast to singly heavy hadrons. Predictions on semileptonic and two-body nonleptonic decays of $…
Nonleptonic two body $B_c$ decays including radially excited $ψ(2S)$ or $η_c(2S)$ mesons in the final state are studied using the perturbative QCD approach based on $k_T$ factorization. The charmonium distribution amplitudes are extracted from the $n = 2, l = 0$ Schr$\ddot{o}$dinger states for the harmonic oscillator potential. Utilizing these distribution amplitudes, we calculate the numerical results of the $B_c\rightarrow ψ(2S),η_c(2S)$ transition form factors and branching fractions of $B_c\rightarrow ψ(2S)π, η_c(2S)π$ decays. The ratio between two decay modes $B_c\rightarrow ψ(2S)π$ and $…
The phenomenology of the so-called X, Y and Z hadronic resonances is hard to reconcile with standard charmonium or bottomonium interpretations. It has been suggested that some of these new hadrons can possibly be described as tightly bound tetraquark states and/or as loosely bound two-meson molecules. In the present paper we focus on the hypothetical existence of flavored, doubly charmed, tetraquarks. Such states might also carry double electric charge, and in this case, if discovered, they could univocally be interpreted in terms of compact tetraquarks. Flavored tetraquarks are also amenable …
We discuss recent progress in lattice QCD studies on various aspects involving strange quarks. Appropriate combinations of conserved net strange and net charm fluctuations and their correlations with other conserved charges provide evidence that in the hadronic phase so far unobserved hadrons contribute to the thermodynamics and need to be included in hadron resonance gas models. In the strange sector this leads to significant reductions of the chemical freeze-out temperature of strange hadrons. In this context, a discussion of data from heavy-ion collisions at SPS, RHIC and LHC on the chemica…
We consider the production of $J/ψ$ and $ψ(2S)$ mesons originating from the decays of $b$-flavored hadrons at the LHC using the $k_T$-factorization approach. Our analysis covers both inclusive charmonia production and production of $J/ψ$ mesons in association with $Z$ bosons. We apply the transverse momentum dependent (or unintegrated) gluon density in a proton derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation and adopt fragmentation functions based on the non-relativistic QCD factorization to describe the inclusive $b$-hadron decays into the different charmonium state…
In the present work, we propose to search the charmonium-like states $Z_c(3900$) and $Z_c(4020)$ in the $B_c$ decay. In an effective Lagrangian approach, the branching ratios of $B_c^+ \to Z_c(3900)^+ π^0$ and $B_c^+\to Z_c (4020)^+ π^0$ are estimated to be of order of $10^{-4}$ and $10^{-7}$, respectively. The large production rate of $Z_c(3900)$ could provide an important source of the production of $Z_c(3900)$ from the semi-exclusive decay of $b$-flavored hadrons reported by D0 Collaboration, which can be tested by the exclusive measurements in LHCb.
We examine the rates for the exclusive decays $B\to K^{(*)}\ell^+\ell^-$. We use the scaling predictions of the heavy quark effective theory to extract the necessary form factors from fits to various combinations of data. These data include the $D\to K^{(*)}\ellν$ semileptonic decays, as well as the nonleptonic decays $B\to K^{(*)}ψ^{(\prime)}$ and the rare decay $B\to K^*γ$. We use different parametrizations of form factors, and find that integrated decay rates are not very sensitive to the forms chosen. However, the decay spectra and the forward-backward asymmetry in $B\to K^*\ell^+\ell^-$ a…
