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Register a new userStudy of $B_{s}$ ${to}$ ${eta}_{c}(J/{psi})D$ decay with perturbative QCD approach
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The $W$-exchange process $B_{s}$ ${to}$ ${eta}_{c}(J/{psi})D$ is studied with the perturbative QCD approach. Three kinds of wave functions for $B_{s}$ meson and two forms of wave functions for charmonium are considered. It is estimated that branching ratios for $B_{s}$ ${to}$ ${eta}_{c}bar{D}$, ${eta}_{c}D$, $J/{psi}bar{D}$, $J/{psi}D$ decays are the order of $10^{-7}$, $10^{-8}$, $10^{-8}$, $10^{-9}$, respectively, where the largest uncertainty is from wave functions. There is a possibility for measuring these decay in the near future.
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In this work, we provide estimates of the branching ratios, direct $CP$ asymmetries and triple product asymmetries in $B_{(s)} to (pipi)(Kpi)$ decays in the perturbative QCD approach, where the $pipi$ and $Kpi$ invariant mass spectra are dominated by the vector resonances $rho(770)$ and $K^*(892)$, respectively. Some scalar backgrounds, such as $f_0(500,980) to pipi$ and $K^*_0(1430) to Kpi$ are also accounted for. The $rho(700)$ is parametrized by the Gounaris-Sakurai function. The relativistic Breit-Wigner formula for the $f_0(500)$ and Flatte model for the $f_0(980)$ are adopted to parameterize the time-like scalar form factors $F_S(omega^2)$. We also use the D.V. Bugg model to parameterize the $f_0(500)$ and compare the relevant theoretical predictions from different models. While in the region of $Kpi$ invariant mass, the $K^*_0(1430)$ is described with the LASS lineshape and the $K^*(892)$ is modeled by the Breit-Wigner function. We find that the decay rates for the considered decay modes agree with currently available data within errors. As a by-product, we extract the branching ratios of two-body decays $B_{(s)} to rho(770)K^*(892)$ from the corresponding four-body decay modes and calculate the relevant polarization fractions. Our prediction of longitudinal polarization fraction for $B^0to rho(770)^0 K^*(892)^0$ decay deviates a lot from the recent LHCb measurement, which should be resolved. It is shown that the direct $CP$ asymmetries are large due to the sizable interference between the tree and penguin contributions, but they are small for the tree-dominant or penguin-dominant processes. The PQCD predictions for the triple product asymmetries are small which are expected in the standard model, and consistent with the current data reported by the LHCb Collaboration.Our results can be tested by the future precise data from the LHCb and Belle II experiments.
Motivated by recent interest in soft $J/Psi$ production in B decays, we investigate ${B}^0 to J/Psi D^{(star)}$ and $eta_c D^{(star)}$ decays in perturbative QCD. We find that, within that framework, these decays are calculable since the heavy $cbar{c}$ pair in the final states is created by a hard gluon. The branching ratios are estimated to be around $10^{-7}sim 10^{-8}$, too small to be consistent with the data, suggesting that other mechanism(s) contribute to the observed excess of soft $J/Psi$ in ${B}^0 to J/Psi + X$ decays. The possibility of the production of a hybrid $s{bar d}g$ meson with mass about 2 GeV is briefly entertained.
A search for the decays $B_c^+ to J/psi D^{(*)0} K^+$ and $B_c^+ to J/psi D^{(*)+} K^{*0}$ is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb$^{-1}$. The decays $B_c^+ to J/psi D^0 K^+$ and $B_c^+ to J/psi D^{*0} K^+$ are observed for the first time, while first evidence is reported for the $B_c^+ to J/psi D^{*+} K^{*0}$ and $B_c^+ to J/psi D^+ K^{*0}$ decays. The branching fractions of these decays are determined relative to the $B_c^+ to J/psi pi^+$ decay. The $B_c^+$ mass is measured, using the $J/psi D^0 K^+$ final state, to be $6274.28 pm 1.40 (stat) pm 0.32 (syst)$ MeV/$c^2$. This is the most precise single measurement of the $B_c^+$ mass to date.
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron colliders
The decay $B_c^+to J/psi K^+$ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 ${,fb}^{-1}$, collected by the LHCb experiment in $pp$ collisions at a centre-of-mass energy of $7mathrm{,Tekern -0.1em V}$. A yield of $46pm12$ events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of $B_c^+to J/psi K^+$ to that of $B_c^+to J/psipi^+$ is measured to be $0.069pm0.019pm0.005$, where the first uncertainty is statistical and the second is systematic.
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