η(c) production at LHC and implications for the understanding of J/ψ production.

We present a complete evaluation for the prompt η_{c} production at the LHC at next-to-leading order in α_{s} in nonrelativistic QCD. By assuming heavy-quark spin symmetry, the recently observed η_{c} production data by LHCb results in a very strong constraint on the upper bound of the color-octet long-distance matrix element ⟨O^{J/ψ}(^{1}S_{0}^{[8]})⟩ of J/ψ. We find this upper bound is consistent with our previous study of the J/ψ yield and polarization and can give good descriptions for the measurements, but the upper bound is inconsistent with some other theoretical estimates. This may provide important information for understanding the nonrelativistic QCD factorization formalism.

Polarizations of χc1 and χc2 in prompt production at the LHC.

Prompt χc production at hadron colliders may provide a unique test for the color-octet mechanism in nonrelativistic QCD. We present an analysis for the polarization observables of χc1 and χc2 at next-to-leading order in αS and propose to measure them at the LHC, which is expected to be important for testing the validity of nonrelativistic QCD.

J/ψ polarization at hadron colliders in nonrelativistic QCD.

With nonrelativistic QCD factorization, we present a full next-to-leading order computation of the polarization observable for J/ψ production at hadron colliders including all important Fock states, i.e., 3S(1)([1,8]), 1S(0)([8]), and 3P(J)([8]). We find the 3P(J)([8]) channel contributes a positive longitudinal component and a negative transverse component, so the J/ψ polarization puzzle may be understood as the transverse components canceling between the 3S(1)([8]) and 3P(J)([8]) channels, which results in mainly the unpolarized (even slightly longitudinally polarized) J/ψ. This may give a possible solution to the long-standing J/ψ polarization puzzle. Predictions for J/ψ polarization at the LHC are also presented.

J/ψ(ψ') production at the Tevatron and LHC at O(α(s)4v4) in nonrelativistic QCD.

We present a complete evaluation for J/ψ(ψ') prompt production at the Tevatron and LHC at next-to-leading order in nonrelativistic QCD, including color-singlet, color-octet, and higher charmonia feeddown contributions. The short-distance coefficients of 3P(J)([8]) at next-to-leading order are found to be larger than leading order by more than an order of magnitude but with a minus sign at high transverse momentum p(T). Two new linear combinations of color-octet matrix elements are obtained from the CDF data, and used to predict J/ψ production at the LHC, which agrees with the CMS data. The possibility of (1)S(0)([8]) dominance and the J/ψ polarization puzzle are also discussed.

QCD corrections to e+e- -->J/psi+gg at B factories.

In heavy quarkonium production, the measured ratio R_{cc[over ]}=sigma[J/psi+cc[over ]+X]/sigma[J/psi+X] at B factories is much larger than existing theoretical predictions. To clarify this discrepancy, in nonrelativistic QCD we find the next-to-leading-order (NLO) QCD correction to e;{+}e;{-}-->J/psi+gg can enhance the cross section by about 20%. Together with the calculated NLO result for e;{+}e;{-}-->J/psi+cc[over ], we show that the NLO corrections can significantly improve the fit to the ratio R_{cc[over ]}. The effects of leading logarithm resummation near the end point on the J/psi momentum distribution and total cross section are also considered. Comparison of the calculated cross section for e;{+}e;{-}-->J/psi+gg with the observed cross section for e;{+}e;{-}-->J/psi+non-(cc[over ]) is expected to provide unique information on the issue of color-octet contributions.

QCD prediction for the non-DD[over ] annihilation decay of psi(3770).

To clarify the marked difference between BES and CLEO measurements on the non-DD[over ] decays of the psi(3770), a 1(3)D1-dominated charmonium, we calculate the annihilation decay of psi(3770) in nonrelativistic QCD. By introducing the color-octet contributions, the results are free from infrared divergences. The color-octet matrix elements are estimated by solving the evolution equations. The S-D mixing effect is found to be very small. With m_{c}=1.5+/-0.1 GeV, our result is Gamma(psi(3770)-->light hadrons)=467(+338);(-187) keV. For mc=1.4 GeV, together with the observed hadronic transitions and E1 transitions, the non-DD[over ] decay branching ratio of psi(3770) could reach about 5%. Our results do not favor the results of either the BES or the CLEO Collaborations, and further experimental tests are urged.

Double-charm production e+e- -->J/psi + cc at B factories with next-to-leading-order QCD corrections.

The inclusive J/psi production in e;{+}e;{-}-->J/psicc at B factories is one of the most challenging open problems in heavy quarkonium physics. The observed cross section of this double-charm production process is larger than existing leading order (LO) QCD predictions by a factor of 5. In the nonrelativistic QCD (NRQCD) factorization formalism, we calculate the next-to-leading order (NLO) QCD virtual and real corrections to this process, and find that these corrections can substantially enhance the cross section with a K factor of about 1.8. We further take into account the feeddown contributions from higher charmonium states [mainly the psi(2S) as well as chi_{cJ}] and the two-photon contributions, and find that the discrepancy between theory and experiment can be largely removed.

Next-to-leading-order QCD correction to e(+)e(-)-->J/psi+eta(c) at sqrt[s]=10.6 GeV.

One of the most challenging open problems in heavy quarkonium physics is the double charm production in e+e- annihilation at B factories. The measured cross section of e+e- --> J/psi + eta(c) is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the cc bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of e+e- --> J/psi + eta(c) at sqrt[s] = 10:6 GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence, it greatly reduces the large discrepancy between theory and experiment.