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Register a new userThe weak $B$, $B_s$ and $B_c$ decays to radially excited states
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Recently, many new excited states of heavy mesons, especially the radially excited states, are discovered. The study of the production processes of these states from the ground b-flavored mesons is of interest. In this paper, we use the improved Bethe-Salpeter method to study the semi-leptonic and non-leptonic decays of $B$, $B_s$, and $B_c$ mesons, where the final states are focused on the radial excited $2S$ and $3S$ states. We find that many channels have branching ratios up to $10^{-4}$, which are within the detection accuracy of current experiments.
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We discuss the possibility to measure in present experiments, especially LHCb, the non leptonic decay branching ratio $B to D pi$, and emphasize phenomenological implications on $B to D l u$ semileptonic decay. We have estimated by lattice QCD the $D$ decay constant $f_{D}$ that parameterizes the $D$ emission contribution to the Class-III non leptonic decay $B^- to D^0 pi^-$. In addition, we provide a new estimate of the decay constants $f_{D_{s,q}}$ which read $f_{D_{s}}=252(3)$ MeV and $f_{D_{s}}/f_{D}=1.23(1)(1)$.
We study the CP violation in two-body nonleptonic decays of $B_c$ meson. We concentrate on the decay channels which contain at least one excited heavy meson in the final states. Specifically, the following channels are considered: $B_cto cbar c(2S, 2P)+bar cq(1S, 1P)$, $B_cto cbar c(1S)+bar cq(2S, 2P)$, $B_cto cbar c(1P)+bar cq(2S)$, $B_cto cbar c(1D)+bar cq(1S, 1P)$, and $B_cto cbar c(3S)+bar cq(1S)$. The improved Bethe-Salpeter method is applied to calculate the hadronic transition matrix element. Our results show that some decay modes have large branching ratios, which is of the order of $10^{-3}$. The CP violation effect in $B_c rightarrow eta_c(1S)+D(2S)$, $B_c rightarrow eta_c(1S)+D_0^{*}(2P)$, and $B_c rightarrow J/psi+D^{*}(2S)$ are most likely to be found. If the detection precision of the CP asymmetry in such channels can reach the $3sigma$ level, at least $10^7$ $B_c$ events are needed.
The BaBar Collaboration has recently reported branching fractions for semileptonic decays of the $B$ meson into final states with charged and neutral $D_{1}(2420)$ and $D_{2}^{ast}(2460)$, two narrow orbitally excited charmed mesons. We evaluate these branching fractions within the framework of a constituent quark model in two steps, one which involves a semileptonic decay and the other one mediated by a strong process. Our results are in agreement with the experimental data.
A search is performed in the invariant mass spectrum of the $B_c^{+}pi^{+}pi^{-}$ system for the excited $B_c^{+}$ states $B_c(2^{1}S_{0})^+$ and $B_c(2^{3}S_{1})^+$ using a data sample of $pp$ collisions collected by the LHCb experiment at the centre-of-mass energy of $sqrt{s} = 8 ,{mathrm{TeV}}$, corresponding to an integrated luminosity of $2 ,{mathrm{fb^{-1}}}$. No evidence is seen for either state. Upper limits on the ratios of the production cross-sections of the $B_c(2^{1}S_{0})^+$ and $B_c(2^{3}S_{1})^+$ states times the branching fractions of ${B_c(2^{1}S_{0})^+} to {B_c^{+}pi^{+}pi^{-}}$ and ${B_c(2^{3}S_{1})^+} to {B_c^{*+}pi^{+}pi^{-}}$ over the production cross-section of the $B_c^{+}$ state are given as a function of their masses. They are found to be between 0.02 and 0.14 at $95%$ confidence level for $B_c(2^{1}S_{0})^+$ and $B_c(2^{3}S_{1})^+$ in the mass ranges $[6830, 6890] ,{mathrm{MeV}}/c^{2}$ and $[6795,6890] ,{mathrm{MeV}}/c^{2}$, respectively.
We study the semileptonic decays of $B_c$ meson to S-wave charmonium states in the framework of relativistic independent quark model based on an average flavor-independent confining potential $U(r)$ in the scalar-vector harmonic form $U(r)=frac{1}{2}(1+gamma^0)(ar^2+V_0)$, where ($a$, $V_0$) are the potential parameters.The form factors for $B_c^+to eta_c /psi e^+ u_e$ transitions are studied in the physical kinematic range. Our predicted branching ratios (BR) for transitions to ground state charmonia are found comparatively large $sim $ $10^{-2}$, compared to those for transitions to radially excited 2S and 3S states. Like all other mpdel predictions, our predicted BR are obtained in the hierarchy: BR($B_c^+to eta_c /psi (3S)$) $<$ BR($B_c^+to eta_c/ psi (2S)$) $<$ BR($B_c^+to eta_c /psi (1S)$). The longitudinal ($Gamma_L$) and transverse polarization ($Gamma_T$) for $B_c to psi(ns)$ decay modes are predicted in the small and large $q^2$ - region as well as in the whole physical region. The ratios for such transitions are obtained $frac {Gamma_L}{Gamma_T} < 1$ throughout the kinematic range which means the $B_c^+$ meson transitions to vector meson charmonium states take place predominantly in transverse polarization mode. The theoretical predictions on these transitions could be tested in the on-going and forthcoming experiments at LHCb.
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