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Register a new userPredictions for $e^+e^-to J/psi eta_c$ with Light-Cone Wave-Functions
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Predictions for $e^+e^-to J/psi eta_c$ from previous studies are made by taking charmonia as a nonrelativistic bound state and by using nonrelativistic QCD(NRQCD) approach. The predicted cross-section is smaller by an order of magnitude than the experimentally observed. We study the process by taking charm quark as a light quark and use light-cone wave-functions to parameterize nonperturbative effects related to charmonia. The total cross section of $e^+e^-to J/psi eta_c$ can be predicted, if these wave-functions are known. Motivated by studies of light-cone wave-functions of light hadrons, we make a reasonable assumption of the forms of light-cone wave-functions. With these light-cone wave-functions we can obtain the cross section which is more closer to the experimentally observed than that from NRQCD approach. We also discuss in detail the difference between two approaches.
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We make a detailed study on the typical production channel of double charmoniums, $e^+e^-to J/psi+eta_c$, at the center-of-mass collision energy $sqrt{s}=10.58$ GeV. The key component of the process is the form factor $F_{rm VP}(q^2)$, which has been calculated within the QCD light-cone sum rules (LCSR). To improve the accuracy of the derived LCSR, we keep the $J/psi$ light-cone distribution amplitude up to twist-4 accuracy. Total cross sections for $e^+e^-to J/psi+eta_c$ at three typical factorization scales are $sigma|_{mu_s} = 22.53^{+3.46}_{-3.49}~{rm fb}$, $sigma|_{mu_k} = 21.98^{+3.35}_{-3.38}~{rm fb}$ and $sigma|_{mu_0} = 21.74^{+3.29}_{-3.33}~{rm fb}$, respectively. The factorization scale dependence is small, and those predictions are consistent with the BABAR and Belle measurements within errors.
In this paper, we present a detailed next-to-leading-order (NLO) study of $J/psi$ angular distributions in $e^{+}e^{-} to J/psi+eta_c,chi_{cJ}$ ($J=0,1,2$) within the nonrelativistic QCD factorization (NRQCD). The numerical NLO expressions for total and differential cross sections, i.e., $frac{dsigma}{dcostheta}=A+Bcos^2theta$, are both derived. With the inclusion of the newly-calculated QCD corrections to $A$ and $B$, the $alpha_{theta}(= B/A)$ parameters in $J/psi+chi_{c0}$ and $J/psi+chi_{c1}$ are moderately enhanced, while the magnitude of ${alpha_theta}_{J/psi+chi_{c2}}$ is significantly reduced; regarding the production of $J/psi+eta_c$, the $alpha_theta$ value remains unchanged. By comparing with experiment, we find the predicted ${alpha_theta}_{J/psi+eta_c}$ is in good agreement with the $textrm{B}scriptsize{textrm{ELLE}}$ measurement; however, ${alpha_theta}_{J/psi+chi_{c0}}$ is still totally incompatible with the experimental result, and this discrepancy seems to hardly be cured by proper choices of the charm-quark mass, the renormalization scale, and the NRQCD matrix elements.
In two recent reactions by Belle producing $Dbar D$ and $Dbar D^*$ meson pairs, peaks above threshold have been measured in the differential cross sections, possibly indicating new resonances in these channels. We want to study such reactions from the point of view that the $D$ meson pairs are produced from already known or predicted resonances below threshold. Our study shows that the peak in the $Dbar D^*$ production is not likely to be caused by the X(3872) resonance, but the peak seen in $Dbar D$ invariant mass can be well described if the $Dbar D$ pair comes from the already predicted scalar X(3700) resonance.
Using a data sample of $448.1times10^6$ $psi(3686)$ events collected at $sqrt{s}=$ 3.686 GeV with the BESIII detector at the BEPCII, we search for the rare decay $J/psi to phi e^+ e^-$ via $psi(3686) to pi^+pi^- J/psi $. No signal events are observed and the upper limit on the branching fraction is set to be $mathcal{B}(J/psi to phi e^+ e^-) < 1.2 times 10^{-7}$ at the 90% confidence level, which is still about one order of magnitude higher than the Standard Model prediction.
We study the possibility of the scalar charmonium and glueball mixing in $e^+ e^-$ annihilation at $sqrt{s}=10.6$ GeV. The effects can be used to explain the unexpected large cross section ($12pm 4$ fb) and the anomalous angular distribution ($alpha= -1.1^{+0.8}_{-0.6}$) of the exclusive $e^+e^-to J/psichi_{c0}$ process observed by Belle experiments at KEKB. We calculate the helicity amplitudes for the process $e^+ e^- to J/psi H(0^{++})$ in NRQCD, where $H(0^{++})$ is the mixed state. We present a detailed analysis on the total cross section and various angular asymmetries which could be useful to reveal the existence of the scalar glueball state.
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