We present a new computation of S-wave color-singlet nonrelativistic QCD matrix elements for the J/ψ and the η c . We compute the matrix elements of leading order in the heavy-quark velocity v and the matrix elements of relative order v 2 . Our computation is based on the electromagnetic decay rates of the J/ψ and the η c and on a potential model that employs the Cornell potential. We include relativistic corrections to the electromagnetic decay rates, resumming a class of corrections to all orders in v, and find that they significantly increase the values of the matrix elements of leading order in v. This increase could have important implications for theoretical predictions for a number of quarkonium decay and production processes. The values that we find for the matrix elements of relative order v 2 are somewhat smaller than the values that one obtains from estimates that are based on the velocity-scaling rules of nonrelativistic QCD.

We present a new calculation, in the nonrelativistic QCD (NRQCD) factorization formalism, of the relativistic corrections to the double-charmonium cross section σ[e + e − → J/ψ + η c ] at the energy of the Belle and BABAR experiments. In comparison with previous work, our calculation contains several refinements. These include the use of the improved results for the nonperturbative NRQCD matrix elements, the resummation of a class of relativistic corrections, the use of the vector-meson-dominance method to calculate the fragmentation contribution to the pure QED amplitude, the inclusion of the effects of the running of α, and the inclusion of the contribution that arises from the interference between the relativistic corrections and the corrections of nextto-leading order in α s . We also present a detailed estimate of the theoretical uncertainty. We conclude that the discrepancy between the theoretical prediction for σ[e + e − → J/ψ + η c ] and the experimental measurements has been resolved.

We construct anomaly-free leptophobic Uð1Þ 0 flavor models with light Z 0 ð$145 GeVÞ. In order to allow renormalizable Yukawa interactions for the standard model chiral fermions, new Higgs doublets with nonzero Uð1Þ 0 charges are introduced. Then the neutral (pseudo)scalar Higgs bosons as well as Z 0 contribute to the t " t and the same sign top pair productions [ðt " tÞ and ðttÞ], and one can evade the strong constraint from ðttÞ. The top forward-backward asymmetry (A FB ) and Wjj excess at CDF could be accommodated by A New FB ¼ 0:084 $ 0:12 and ðWjjÞ & Oð10Þ pb  sin 2 2.

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Based on the nonrelativistic QCD (NRQCD) factorization formalism, we investigate inclusive productions of two spin-triplet S-wave quarkonia pp->2J/psi+X, 2Upsilon+X, and J/psi+Upsilon+X at the CERN Large Hadron Collider. The total production rates integrated over the rapidity (y) and transverse-momentum (p_T) ranges |y|<2.4 and p_T<50 GGeV are predicted to be sigma[pp->2J/psi+X] = 22 (35) nb, sigma[pp->2Upsilon+X] = 24 (49) pb, and sigma[pp->J/psi+Upsilon+X] = 7 (13) pb at the center-of-momentum energy sqrt{s} = 7 (14) TeV. In order to provide predictions that can be useful in both small- and large-p_T regions, we do not employ the fragmentation approximation and we include the spin-triplet S-wave color-singlet and color-octet channels for each quarkonium final state at leading order in the strong coupling. The p_T distributions of pp->2J/psi+X and 2Upsilon+X in the low-p_T region are dominated by the color-singlet contributions. At leading order in the strong coupling, the color-singlet channel is absent for pp->J/psi+Upsilon+X. Therefore, the process pp->J/psi+Upsilon+X may provide a useful probe to the color-octet mechanism of NRQCD.Comment: 26 pages, 7 figures, 3 tables, version published in JHE