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Register a new userSemileptonic and nonleptonic B decays to three charm quarks: B->J/psi (eta_c) D l nu and J/psi (eta_c) D pi
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We evaluate the form factors describing the semileptonic decays $bar{B^0}to J/psi (eta_c) D^+ ell^- bar u_ell$, within the framework of a QCD relativistic potential model. This decay is complementary to $bar{B^0}to J/psi (eta_c) D^+ pi^-$ in a phase space region where a pion factors out.We estimate the branching ratio for these semileptonic and nonleptonic channels, finding $mathcal{BR}(bar{B^0} to J/psi (eta_c) D^+ ell u_ell) simeq 10^{-13}$, $mathcal{BR}(bar{B^0} to J/psi D^+ pi^-) = 3.1 times 10^{-8}$ and $mathcal{BR}(bar{B^0} to eta_c D^+ pi^-) = 3.5 times 10^{-8}$.
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We present a study of the inclusive photon spectrum from 6.3 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/psi -> eta_c gamma, eta_c width and mass. Taking into account an asymmetric photon line shape we obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4 +- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.
Based on $(106.41 pm 0.86)times 10^{6}$ $psi(3686)$ events collected with the BESIII detector at the BEPCII collider, the branching fractions of $psi(3686) to pi^+pi^- J/psi$, $J/psi to e^+e^- $, and $J/psi to mu^+mu^-$ are measured. We obtain ${cal B}[psi(3686) to pi^+pi^-J/psi]=(34.98pm 0.02pm 0.45)%$, ${cal B}[J/psi to e^+e^-] = (5.983 pm 0.007 pm 0.037)%$ and ${cal B}[J/psi to mu^+mu^-] = (5.973 pm 0.007 pm 0.038)%$. The measurement of ${cal B}[psi(3686) to pi^{+}pi^{-}J/psi]$ confirms the CLEO-c measurement, and is apparently larger than the others. The measured $J/psi$ leptonic decay branching fractions agree with previous experiments within one standard deviation. These results lead to ${cal B}[J/psi to l^+l^-] = (5.978 pm 0.005 pm 0.040)%$ by averaging over the $e^{+}e^{-}$ and $mu^{+}mu^{-}$ channels and a ratio of ${cal B}[J/psi to e^+e^-] / {cal B}[J/psi to mu^+mu^-] = 1.0017 pm 0.0017 pm 0.0033$, which tests $e$-$mu$ universality at the four tenths of a percent level. All the measurements presented in this paper are the most precise in the world to date.
Recently, the deviation of the ratios $R(D)$, $R(D^{*})$ and $R(J/psi)$ have been found between experimental data and the Standard Model predictions, which may be the hint of New Physics. In this work, we calculate these ratios within the Standard Model by using the improved instantaneous Bethe-Salpeter method. The emphasis is pad to the relativistic correction of the form factors. The results are $R(D)=0.312 ^{+0.006}_{-0.007}$, $R(D^*)= 0.249^{+0.001}_{-0.002}$, $R(D_s)=0.320 ^{+0.009}_{-0.009}$, $R(D^*_s)=0.251 ^{+0.002}_{-0.003}$, $R(eta_c)=0.384 ^{+0.032}_{-0.042}$, and $R(J/psi)=0.267 ^{+0.009}_{-0.011}$, which are consistent with predictions of other models and the experimental data. The semileptonic decay rates and corresponding form factors at zero recoil are also given.
We study the semileptonic decay of the $B_c (0^-)$ to charmonia through the bottom-to-charm-quark electroweak current in the framework of basis light-front quantization. Explicitly, we calculate the weak transition form factors for processes of $B_c$ decaying into $eta_c$ or $J/psi$ based on the corresponding initial and final valence light-front wave functions both obtained from the basis light-front quantization. We also present the corresponding differential decay width and branching ratios, as well as the branching ratios for decays into the $eta_c$ and the $psi$. We observe unphysical frame dependence of the calculated form factors, which is attributed to only including the valence light-front wave functions. Based on the analysis of current component, we propose a preferred set of frames to calculate these form factors.
We analyze two recent reactions of Belle, producing $Dbar D$ and $Dbar D^*$ states that have an enhancement of the invariant $Dbar D$, $Dbar D^*$ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below $Dbar D$ or $Dbar D^*$ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the $Dbar D^*$ spectrum above threshold is, however, unlikely to be due to a threshold enhancement produced by the presence, below threshold, of the hidden charm axial vector meson X(3872).
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