Factorisation in higher-twist single-spin amplitudes

Authors
Citation
Pg. Ratcliffe, Factorisation in higher-twist single-spin amplitudes, EUR PHY J C, 8(3), 1999, pp. 403-408
Citations number
33
Categorie Soggetti
Physics
Journal title
EUROPEAN PHYSICAL JOURNAL C
ISSN journal
14346044 → ACNP
Volume
8
Issue
3
Year of publication
1999
Pages
403 - 408
Database
ISI
SICI code
1434-6044(199905)8:3<403:FIHSA>2.0.ZU;2-P
Abstract
We analyse the twist-three amplitudes that can give rise to single-spin asy mmetries in hadron-hadron scattering; in so doing we bring to light a novel factorisation property. As already known, the requirement of an imaginary part leads to consideration of twist-three contributions that are also rela ted to transverse spin in deep-inelastic scattering. In particular, when an external line becomes soft in contributions arising from three-parton corr elators, the imaginary part of an internal propagator may be exposed. As sh own here, it is precisely this kinematical configuration that permits the f actorisation. An important feature is the resulting simplification: the cal culation of tens of Feynman diagrams normally contributing to such processe s is reduced to the evaluation of products of the simple factors derived he re and known two-body helicity amplitudes. We thus find clarifying relation s between the spin-dependent and spin-averaged cross-sections and formulate a series of selection rules. In addition, the kinematical dependence of su ch asymmetries, is rendered more transparent.