6,003 research outputs found
Note on differential operators, CHY integrands, and unifying relations for amplitudes
An elegant unified web for amplitudes of various theories was given by
Cachazo, He and Yuan in the CHY framework a few years ago. Recently, similar
web has also been constructed by Cheung, Shen and Wen, which relies on a set of
differential operators. In this note, by acting these differential operators on
CHY-integrands systematically, we have established the relation between these
two approaches. Thus, amplitudes for all theories which have CHY
representations, include gravity theory, Einstein-Yang-Mills theory,
Einstein-Maxwell theory, pure Yang-Mills theory, Yang-Mills-scalar theory,
Born-Infeld theory, Dirac-Born-Infeld theory and its extension, bi-adjoint
scalar theory, theory, non-linear sigma model, as well as special
Galileon theory, have been included in the unified web rooted from gravity
theory.Comment: 20 page
Single transverse spin asymmetry of prompt photon production
We study the single transverse spin asymmetry of prompt photon production in
high energy proton-proton scattering. We include the contributions from both
the direct and fragmentation photons. While the asymmetry for direct photon
production receives only the Sivers type of contribution, the asymmetry for
fragmentation photons receives both the Sivers and Collins types of
contributions. We make a model calculation for quark-to-photon Collins
function, which is then used to estimate the Collins asymmetry for
fragmentation photons. We find that the Collins asymmetry for fragmentation
photons is very small, thus the single transverse spin asymmetry of prompt
photon production is mainly coming from the Sivers asymmetry in direct and
fragmentation photons. We make predictions for the prompt photon spin asymmetry
at RHIC energy, and emphasize the importance of such a measurement.Comment: 11 pages 7 figures, additional discussion, 1 figure added, matches
published version in Phys. Lett.
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