97,961 research outputs found
Gluon GPDs and Exclusive Photoproduction of a Quarkonium in Forward Region
Forward photoproduction of can be used to extract Generalized Parton
Distributions(GPD's) of gluons. We analyze the process at twist-3 level and
study relevant classifications of twist-3 gluon GPD's. At leading power or
twist-2 level the produced is transversely polarized. We find that at
twist-3 the produced is longitudinally polarized. Our study shows that
in high energy limit the twist-3 amplitude is only suppressed by the inverse
power of the heavy quark mass relatively to the twist-2 amplitude. This
indicates that the power correction to the cross-section of unpolarized
can have a sizeable effect. We have also derived the amplitude of the
production of at twist-3, but the result contains end-point
singularities. The production of other quarkonia has been briefly discussed.Comment: Discussions of results are adde
Levinson's theorem for the Schr\"{o}dinger equation in two dimensions
Levinson's theorem for the Schr\"{o}dinger equation with a cylindrically
symmetric potential in two dimensions is re-established by the Sturm-Liouville
theorem. The critical case, where the Schr\"{o}dinger equation has a finite
zero-energy solution, is analyzed in detail. It is shown that, in comparison
with Levinson's theorem in non-critical case, the half bound state for
wave, in which the wave function for the zero-energy solution does not decay
fast enough at infinity to be square integrable, will cause the phase shift of
wave at zero energy to increase an additional .Comment: Latex 11 pages, no figure and accepted by P.R.A (in August); Email:
[email protected], [email protected]
Transverse spin effects of sea quarks in unpolarized nucleons
We calculate the non-zero Boer-Mulders functions of sea quarks inside the
proton in a meson-baryon fluctuation model. The results show that the
transverse spin effects of sea quarks in an unpolarized nucleon are sizable.
Using the obtained antiquark Boer-Mulders functions, we estimate the asymmetries in the unpolarized and Drell-Yan processes at FNAL
E866/NuSea experiments. The prediction for the asymmetries in the
unpolarized Drell-Yan process at the BNL Relativistic Heavy Ion Collider
(RHIC) is also given.Comment: 7 pages, 5 figures, to appear in Physical Review
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