Predictions for single spin asymmetries in $\ell p^{\uparrow} \to \pi X$ and $\gamma^* p^{\uparrow} \to \pi X$

M. Anselmino; M. Boglione; J. Hansson; F. Murgia

doi:doi:10.1007/s100520000339

2022 Impact factor 4.4

Particles and Fields

Eur. Phys. J. C 13, 519-526
DOI 10.1007/s100520000339

Predictions for single spin asymmetries
in $\ell p^{\uparrow} \to \pi X$ and $\gamma^* p^{\uparrow} \to \pi X$

M. Anselmino¹ - M. Boglione² - J. Hansson³ - F. Murgia⁴

¹ Dipartimento di Fisica Teorica, Università di Torino and INFN, Sezione di Torino, Via P. Giuria 1, 10125 Torino, Italy
² Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam,
The Netherlands
³ Department of Physics, Luleå University of Technology, 971 87 Luleå, Sweden
⁴ Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari and Dipartimento di Fisica, Università di Cagliari, C.P. 170,
09042 Monserrato (CA), Italy

Received: 29 September 1999 / Published online: 6 March 2000 - © Springer-Verlag 2000

Abstract
Predictions for the single transverse spin asymmetry A_N in semi-inclusive DIS processes are given; non-negligible values of A_N may arise from spin effects in the fragmentation of a polarized quark into a final hadron with a transverse momentum $\mbox{\boldmath$k$ }_\perp$ with respect to the jet axis, the so-called Collins effect. The elementary single spin asymmetry of the fragmenting quark has been fixed in a previous paper, by fitting data on $p^\uparrow p \to \pi X$ , and by assuming that the QCD factorization theorem holds also when transverse momenta are taken into account. The predictions given here are based on the assumption that the Collins effect is the only cause of the observed single spin asymmetries in $p^\uparrow p \to \pi X$ . Eventual spin and $\mbox{\boldmath$k$ }_\perp$ dependences in the quark distribution functions, the so-called Sivers effect, are also discussed.