5,642 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
Three-loop planar master integrals for heavy-to-light form factors
We calculate analytically the three-loop planar master integrals relevant for
heavy-to-light form factors using the method of differential equations. After
choosing a proper canonical basis, the boundary conditions are easy to be
determined, and the solution of differential equations is greatly simplified.
The results for seventy-one master integrals at general kinematics are all
expressed in terms of harmonic polylogarithms.Comment: 18 pages, 2 figure
First-principles investigation of dynamical properties of molecular devices under a steplike pulse
We report a computationally tractable approach to first principles
investigation of time-dependent current of molecular devices under a step-like
pulse. For molecular devices, all the resonant states below Fermi level
contribute to the time-dependent current. Hence calculation beyond wideband
limit must be carried out for a quantitative analysis of transient dynamics of
molecules devices. Based on the exact non-equilibrium Green's function (NEGF)
formalism of calculating the transient current in Ref.\onlinecite{Maciejko}, we
develop two approximate schemes going beyond the wideband limit, they are all
suitable for first principles calculation using the NEGF combined with density
functional theory. Benchmark test has been done by comparing with the exact
solution of a single level quantum dot system. Good agreement has been reached
for two approximate schemes. As an application, we calculate the transient
current using the first approximated formula with opposite voltage
in two molecular structures: Al--Al and Al--Al. As illustrated in these examples, our formalism can be easily
implemented for real molecular devices. Importantly, our new formula has
captured the essential physics of dynamical properties of molecular devices and
gives the correct steady state current at and .Comment: 15 pages, 8 figure
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