General partonic structure for hadronic spin asymmetries

Journal Article · Sun Jan 01 04:00:00 EST 2006 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.73.014020· OSTI ID:20774605

Anselmino, M; Boglione, M ^[1]; D'Alesio, U; Melis, S; Murgia, F ^[2]; Leader, E ^[3]

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1. Dipartimento di Fisica Teorica, Universita di Torino and INFN, Sezione di Torino, Via P. Giuria 1, I-10125 Turin (Italy)
2. INFN, Sezione di Cagliari and Dipartimento di Fisica, Universita di Cagliari, C.P. 170, I-09042 Monserrato (Canada) (Italy)
3. Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom)

The high energy and large p{sub T} inclusive polarized process, (A,S{sub A})+(B,S{sub B}){yields}C+X, is considered under the assumption of a generalized QCD factorization scheme. For the first time all transverse motions, of partons in hadrons and of hadrons in fragmenting partons, are explicitly taken into account; the elementary interactions are computed at leading order with noncollinear exact kinematics, which introduces many phases in the expressions of their helicity amplitudes. Several new spin and k{sub perpendicular} dependent soft functions appear and contribute to the cross sections and to spin asymmetries; we put emphasis on their partonic interpretation, in terms of quark and gluon polarizations inside polarized hadrons. Connections with other notations and further information are given in some Appendixes. The formal expressions for single and double spin asymmetries are derived. The transverse single spin asymmetry A{sub N}, for p{sup {up_arrow}}p{yields}{pi}X processes is considered in more detail, and all contributions are evaluated numerically by saturating unknown functions with their upper positivity bounds. It is shown that the integration of the phases arising from the noncollinear kinematics strongly suppresses most contributions to the single spin asymmetry, leaving at work predominantly the Sivers effect and, to a lesser extent, the Collins mechanism.

• OSTI ID: 20774605
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 1 Vol. 73; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
ASYMMETRY
CROSS SECTIONS
FACTORIZATION
GLUONS
HADRONS
HELICITY
INCLUSIVE INTERACTIONS
POLARIZATION
QUANTUM CHROMODYNAMICS
QUARKS
SPIN
TRANSVERSE MOMENTUM