# General partonic structure for hadronic spin asymmetries

## Abstract

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.

- Authors:

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

- Publication Date:

- OSTI Identifier:
- 20774605

- Resource Type:
- Journal Article

- Resource Relation:
- Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 1; Other Information: DOI: 10.1103/PhysRevD.73.014020; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)

- Country of Publication:
- United States

- Language:
- English

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

### Citation Formats

```
Anselmino, M., Boglione, M., D'Alesio, U., Melis, S., Murgia, F., and Leader, E..
```*General partonic structure for hadronic spin asymmetries*. United States: N. p., 2006.
Web. doi:10.1103/PhysRevD.73.014020.

```
Anselmino, M., Boglione, M., D'Alesio, U., Melis, S., Murgia, F., & Leader, E..
```*General partonic structure for hadronic spin asymmetries*. United States. doi:10.1103/PhysRevD.73.014020.

```
Anselmino, M., Boglione, M., D'Alesio, U., Melis, S., Murgia, F., and Leader, E.. Sun .
"General partonic structure for hadronic spin asymmetries". United States.
doi:10.1103/PhysRevD.73.014020.
```

```
@article{osti_20774605,
```

title = {General partonic structure for hadronic spin asymmetries},

author = {Anselmino, M. and Boglione, M. and D'Alesio, U. and Melis, S. and Murgia, F. and Leader, E.},

abstractNote = {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.},

doi = {10.1103/PhysRevD.73.014020},

journal = {Physical Review. D, Particles Fields},

number = 1,

volume = 73,

place = {United States},

year = {Sun Jan 01 00:00:00 EST 2006},

month = {Sun Jan 01 00:00:00 EST 2006}

}