Related papers: Double charmonium production at B-factories within…
A detailed theoretical derivation of the cross sections of $e^+e^- \to e^+e^-$ and $e^+e^- \to \mu^+\mu^-$ around the $J/\psi$ resonance is reported. The resonance and interference parts of the cross sections, related to $J/\psi$ resonance…
Light front formalism for composite systems is presented. Derivation of equations for bound state and scattering problems are given. Methods of constructing of elastic form factors and scattering amplitudes of composite particles are…
We investigate E1 radiative transitions within charmonium in a relativistic approach based on light-front QCD. In quantum field theory, two sets of processes are pure E1: $\chi_{c0} \to J/\psi \gamma$ ($\psi\to \chi_{c0}\gamma$) and $h_c…
Exclusive quarkonium pair production in electron-positron collisions is studied in non-relativistic QCD. The obtained cross section for J/\psi + \eta_c production in the leading order is confronted against the recent measurements by the…
We discuss duality in ``two-photon''-like processes in the scalar $\varphi^3_E$ model and also in the process $\gamma^*\gamma\to\pi\pi$ in QCD. Duality implies the equivalence between two distinct nonperturbative mechanisms. These two…
A group theoretical procedure for parametrizing non-forward matrix elements of non-local QCD operators is introduced. The related (two-variable) distribution amplitudes are given as sum over power corrections of the double distributions.…
In the article, we study pair production of $\psi[1S]$ and $\psi[2S]$ charmonium states in the forward rapidity region of the LHCb experiment at the $\sqrt{s} = 13$ TeV using the improved color evaporation model and the parton Reggeization…
We calculate the polarization of prompt $J/\psi$ production in the improved color evaporation model at leading order employing the $k_T$-factorization approach. In this paper, we present the polarization parameter $\lambda_\vartheta$ of…
Recent measurements by the Belle Collaboration of the exclusive production of two charmonia in e^+ e^- annihilation differ substantially from theoretical predictions. We suggest that a significant part of the discrepancy can be explained by…
Cross sections of the process $e^+e^-\to\pi^0\pi^0 J/\psi$ at center-of-mass energies between 3.808 and 4.600 GeV are measured with high precision by using 12.4 $fb^{-1}$ of data samples collected with the BESIII detector operating at the…
The cross section of the process $e^+e^- \rightarrow \eta'J/\psi$ is measured at center-of-mass energies from $\sqrt{s} =$ 4.178 to 4.600 GeV using data samples corresponding to a total integrated luminosity of 11 fb$^{-1}$ collected with…
In this paper, we calculate twist-2 light-cone distribution amplitudes (LCDAs) of the S-wave and P-wave quarkonia (namely $^1S_0$ state $\eta_{Q}$, $^3S_1$ state $J/\psi(\Upsilon)$, $^1P_1$ state $h_{Q}$ and $^3P_J$ states $\chi_{QJ}$ with…
Using data samples with an integrated luminosity of $6.4$~fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, the process of $e^+e^-\to\gamma\phi J/\psi$ is studied. The processes of $e^+e^-\to\phi\chi_{c1,c2}$,…
Non-relativistic quantum chromodynamics (NRQCD) factorization formulism is an important approach to investigate the production of the heavy quarkonium. In this paper, we study the production of the $\Omega_{ccc}$ and $\Omega_{bbb}$ at the…
It is shown that difficulties in reconciling the values of the cross section e+e- -> J/psi+eta_c measured at BELLE and calculated within non-relativistic QCD (NRQCD) are caused not by some misinterpretation of the data or other exotic…
In this paper, we present an improved calculation for the decay rate of the rare $Z$-boson decay into $J/\psi + J/\psi$. This decay is dominated by the photon fragmentation mechanism, i.e., the transition $Z\to J/\psi + \gamma^{*}$ followed…
We present a formalism which uses fluxes of equivalent photons including transverse momenta of the intermediate photons. The formalism reminds the familiar $k_t$-factorization approach used, e.g., to study the two-photon production of…
At present the color-octet mechanism is still an important and debatable part in the non-relativistic QCD(NRQCD). We find in this work that the polarized double charmonium production at the LHC may pose a stringent test on the charmonium…
Using the helicity formalism, we calculate the combined angular distribution function of the two gamma photons ($\gamma_1$ and $\gamma_2$) and the electron ($e^-$) in the triple cascade process…
We study the process $\gamma \gamma \to J/\psi \omega$ using a data sample of 519.2 $fb^{-1}$ recorded by the BaBar detector at SLAC at the PEP-II asymmetric-energy $e^+ e^-$ collider at center-of-mass energies near the $\Upsilon(nS)$ ($n =…