468 research outputs found
QCD corrections to double J/\psi production in e+e- annihilation at \sqrt{s}=10.6 GeV
Next-to-Leading-Order(NLO) QCD corrections to double J/psi production in
e^+e^- annihilation at sqrt{s}=10.6 GeV are calculated. We find that they
greatly decrease the cross section, with a K factor (NLO/LO) ranging from -0.31
to 0.25 depending on the renormalization scale. Although the renormalization
scale dependence indicates a large uncertainty, when combined with the NLO QCD
corrections to J/psi + eta_c production, it can explain why the double J/psi$
production could not be found at B factories while the J/psi + eta_c production
could, despite the fact that cross section of the former is larger than that of
the latter at LO by a factor of 1.8.Comment: 4 pages, 4 figures, use revtex
QCD corrections to J/psi plus eta_c production in e+e- annihilation at sqrt{s}=10.6 GeV
Next-to-Leading-Order(NLO) QCD corrections to J/jpsi plus eta_c production in
e+e- annihilation at sqrt{s}=10.6 GeV is calculated in this paper, and an
analytic result is obtained. By choosing proper physical parameters, a K factor
(ratio of NLO to LO) of about 2, which is in agreement with the result in
Ref.\cite{Zhang:2005ch}, is obtained. Our results show that the
Next-Next-to-Leading-Order(NNLO) corrections might be quite large. The plot of
the K-factor vs the center-of-mass energy sqrt{s} shows that it is more
difficult to obtain a convergent result from the perturbative QCD without
resummation of ln(s/m_c) terms as the sqrt{s} becomes larger.Comment: 8 pages, 6 figures, two column
QCD corrections to Upsilon production via color-octet states at the Tevatron and LHC
The NLO QCD corrections to Upsilon production via S-wave color-octet states
Upsilon(^1S_0^8,^3S_1^8) at the Tevatron and LHC is calculated. The K factors
of total cross section (ratio of NLO to LO) are 1.313 and 1.379 for
Upsilon(^1S_0^8) and Upsilon(^3S_1^8) at the Tevatron, while at the LHC they
are 1.044 and 1.182, respectively. By fitting the experimental data from the
D0, the matrix elements for S-wave color-octet states are obtained. And new
predictions for Upsilon production are presented. The prediction for the
polarization of inclusive Upsilon contains large uncertainty rising from the
polarization of Upsilon from feed-down of chi_b. To further clarify the
situation, new measurements on the production and polarization for direct
Upsilon are expected.Comment: 13 pages, 10 Figure
QCD corrections to polarization of J/\psi and \Upsilon at Fermilab Tevatron and CERN LHC
In this work, we present more detail of the calculation on the NLO QCD
corrections to polarization of direct J/psi production via color singlet at
Tevatron and LHC, as well as the results for Upsilon for the first time. Our
results show that the J/psi polarization status drastically changes from
transverse polarization dominant at LO into longitudinal polarization dominant
in the whole range of the transverse momentum of J/psi when the NLO
corrections are counted. For Upsilon production, the p_t distribution of the
polarization status behaves almost the same as that for J/psi except that the
NLO result is transverse polarization at small p_t range. Although the
theoretical evaluation predicts a larger longitudinal polarization than the
measured value at Tevatron, it may provide a solution towards the previous
large discrepancy for J/psi and Upsilon polarization between theoretical
predication and experimental measurement, and suggests that the next important
step is to calculate the NLO corrections to hadronproduction of color octet
state J/psi^(8) and Upsilon^(8). Our calculations are performed in two ways,
namely we do and do not analytically sum over the polarizations, and then check
them with each other.Comment: 12 pages, 12 figures, two columns, use revtex4; to appear in PR
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