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Register a new userWeak decays of $J/psi$: the non-leptonic case
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In our previous study, we calculated the transition from factors of $J/psito D^{(*)}_{(s)}$ using the QCD sum rules. Based on the factorization approximation, the obtained form factors can be applied to evaluate the weak non-leptonic decay rates of $J/psito D^{(*)}_{(s)}+M$, where $M$ stands for a light pseudoscalar or vector meson. We predict that the branching ratio for inclusive non-leptonic two-body weak decays of $J/psi$ which are realized via the spectator mechanism, can be as large as $1.3 times 10^{-8}$, in particular, the branching ratio of $J/psito D^{*pm}_s+rho^mp$ can reach $5.3 times 10^{-9}$. Such values will be marginally accessed by the ability of BESIII which will begin running very soon.
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Within the Standard Model, we investigate the semi-leptonic weak decays of $J/psi$. The various form factors of $J/psi$ transiting to a single charmed meson ($D^{(*)}_{(d,s)}$) are studied in the framework of the QCD sum rules. These form factors fully determine the rates of the weak semi-leptonic decays of $J/psi$ and provide valuable information about the non-perturbative QCD effects. Our results indicate that the decay rate of the semi-leptonic weak decay mode $J/psi to D^{(*)-}_{s}+e^{+}+ u_{e}$ is at order of $10^{-10}$.
The recent experimental developments require a more precise theoretical study of weak decays of heavy baryon $Lambda_b^0$. In this work, we provide an updated and systematic analysis of both the semi-leptonic and nonleptonic decays of $Lambda^0_b$ into baryons $Lambda^+_c$, $Lambda$, $p$, and $n$. The diquark approximation is adopted so that the methods developed in the $B$ meson system can be extended into the baryon system. The baryon-to-baryon transition form factors are calculated in the framework of a covariant light-front quark model. The form factors $f_3, ~g_3$ can be extracted and are found to be non-negligible. The semi-leptonic processes of $Lambda^0_bto Lambda^+_c(p)l^-bar u_l$ are calculated and the results are consistent with the experiment. We study the non-leptonic processes within the QCD factorization approach. The decay amplitudes are calculated at the next-to-leading order in strong coupling constant $alpha_s$. We calculate the non-leptonic decays of $Lambda^0_b$ into a baryon and a s-wave meson (pseudoscalar or vector) including 44 processes in total. The branching ratios and direct CP asymmetries are predicted. The numerical results are compared to the experimental data and those in the other theoretical approaches. Our results show validity of the diquark approximation and application of QCD factorization approach into the heavy baryon system.
A measurement of the number of $J/psi$ events collected with the BESIII detector in 2009 and 2012 is performed using inclusive decays of the $J/psi$ . The number of $J/psi$ events taken in 2009 is recalculated to be $(223.7pm1.4)times 10^6$, which is in good agreement with the previous measurement, but with significantly improved precision due to improvements in the BESIII software. The number of $J/psi$ events taken in 2012 is determined to be $(1086.9pm 6.0)times 10^6$. In total, the number of $J/psi$ events collected with the BESIII detector is measured to be $(1310.6pm 7.0)times 10^6$, where the uncertainty is dominated by systematic effects and the statistical uncertainty is negligible.
We report a new precise determination of the leptonic widths of the J/psi meson performed with the KEDR detector at the VEPP-4M $e^{+}e^{-}$ collider. The measured values of the J/psi parameters are: Gamma_{ee}timesGamma_{ee}/Gamma = 0.3323 pm 0.0064 (stat.) pm 0.0048 (syst.) keV Gamma_{ee}timesGamma_{mumu}/Gamma=0.3318 pm 0.0052 (stat.) pm 0.0063 (syst.) keV. Assuming $emu$ universality and using the table value of the branching ratios the leptonic Gamma_{ll}= 5.59 pm 0.12 keV width and the total Gamma=94.1 pm 2.7 keV widths were obtained. We also discuss in detail a method to calculate radiative corrections at a narrow resonance.
Using a sample of $2.25times 10^8$ $J/psi$ events collected with the BESIII detector at the BEPCII collider, we search for the $J/psi$ semi-leptonic weak decay $J/psi to D^{-}_{s} e^{+} u_{e}+c.c.$ with a much higher sensitivity than previous searches. We also perform the first search for $J/psi to D^{*-}_{s} e^{+} u_{e}+c.c.$ No significant excess of a signal above background is observed in either channel. At the $90%$ confidence level, the upper limits are determined to be $mathcal{B}(J/psi to D^{-}_{s}e^{+} u_{e}+c.c.)<1.3times10^{-6}$ and $mathcal{B}(J/psi to {D^{*}_{s}}^{-}e^{+} u_{e}+c.c.)<1.8times10^{-6}$, respectively. Both are consistent with Standard Model predictions.
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