9,179 research outputs found
Expanding Einstein-Yang-Mills by Yang-Mills in CHY frame
Using the Cachazo-He-Yuan (CHY) formalism, we prove a recursive expansion of
tree level single trace Einstein-Yang-Mills (EYM) amplitudes with arbitrary
number of gluons and gravitons, which is valid for general spacetime dimensions
and any helicity configurations. The recursion is written in terms of
fewer-graviton EYM amplitudes and pure Yang-Mills (YM) amplitudes, which can be
further carried out until we reach an expansion in terms of pure YM amplitudes
in Kleiss-Kuijf (KK) basis. Our expansion then generates naturally a spanning
tree structure rooted on gluons whose vertices are gravitons. We further
propose a set of graph theoretical rules based on spanning trees that evaluate
directly the pure YM expansion coefficients.Comment: 36 pages, 3 captioned figures; v2: more details added, revised and
published versio
Double longitudinal-spin asymmetries in production at RHIC
The double longitudinal-spin asymmetry, , of the production
in polarized proton-proton collisions is presented in this paper at QCD
next-to-leading order. It is found that the obtained values of are in
general consistent with the PHENIX measurements. Various sets of the
long-distance matrix elements (LDMEs) are employed in our calculation to study
the possible theoretical uncertainties. It is found that, for p_t<5\gev, all
these LDMEs lead to almost the same results, which are within the tolerance of
the experimental data uncertainties
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