Understanding the cross section of $e^+e^-\to \eta J/\psi$ process via nonrelativistic QCD
Motivated by the large cross section of $e^+e^-\to \eta J/\psi$ process measured by the BESIII and Belle Collaborations recently, we evaluate this process at $\mathcal{O}(\alpha_s^4)$ accuracy in the framework of nonrelativistic QCD. We find that the cross section at the center-of-mass energy $\sqrt{s}=4.009$ {GeV} is $34.6\mathrm{pb}$, which is consistent with the BESIII data. The comparison with the Belle data in the region from $4.0\ \mathrm{GeV}$ to $5.3\ \mathrm{GeV}$ is also presented. Concerning the $\eta$ and $\eta^\prime$ mixing and the potential gluonium component of $\eta^\prime$, we also estimate the rate of $e^+e^-\to \eta^\prime J/\psi$ process, which can be checked within the updated Belle data.

title: Estimation of semileptonic decays of $B_c$ meson to S-wave charmonia with nonrelativistic QCD
abstract: We study the semileptonic differential decay rates of the B-c meson to S-wave charmonia, eta(c), and J/Psi at next-to-leading order accuracy in the framework of nonrelativistic QCD. In the heavy quark limit, m(b) -> infinity, we obtain analytically the asymptotic expression for the ratio of the next-to-leading order form factor to the leading-order form factor. Numerical results show that the convergence of the ratio is perfect. At the maximum recoil region, we analyze the differential decay rates in detail with various input parameters and polarizations of J/Psi, which can now be checked in the LHCb experiment. Phenomenologically, the form factors are extrapolated to the minimal recoil region, and then the B-c-to-charmonium semileptonic decay rates are estimated.

title: Low transverse momentum heavy quark pair production to probe gluon tomography
abstract: We derive the transverse momentum dependent (TMD) factorization for heavy quark pair production in deep inelastic scattering, where the total transverse momentum is much smaller than the invariant mass of the pair. The factorization is demonstrated at one-loop order, in both Ji–Ma–Yuan and Collins-11 schemes for the TMD definitions, and the hard factors are calculated accordingly. Our result provides a solid theoretical foundation for the phenomenological investigations of the gluon TMDs in this process, and can be extended to other similar hard processes, including di-jet (di-hadron) production in DIS.

title: B$_c$ exclusive decays to charmonium and a light meson at next-to-leading order accuracy
abstract: In this paper the next-to-leading order (NLO) corrections to $B_c$ meson exclusive decays to S-wave charmonia and light pseudoscalar or vector mesons, i.e. $\pi$, $K$, $\rho$, and $K^*$, are performed within non-relativistic (NR) QCD approach. The non-factorizable contribution is included, which is absent in traditional naive factorization (NF). And the theoretical uncertainties for their branching ratios are reduced compared with that of direct tree level calculation. Numerical results show that NLO QCD corrections markedly enhance the branching ratio with a K factor of 1.75 for $B_{c}^{\pm}\to \eta_{c} \pi^{\pm}$ and 1.31 for $B_{c}^{\pm}\to J/\psi \pi^{\pm}$. In order to investigate the asymptotic behavior, the analytic form is obtained in the heavy quark limit, i.e. $m_b \to \infty$. We note that annihilation topologies contribute trivia in this limit, and the corrections at leading order in $z= m_c/m_b$ expansion come from form factors and hard spectator interactions. At last, some related phenomenologies are also discussed.

title: Measurement of D+(s) and D*+(s) production in B meson decays and from continuum e+ e- annihilations at s**(1/2) = 10.6-GeV.