Eur. Phys. J. C (2007) 50: 823-828
https://doi.org/10.1140/epjc/s10052-007-0251-5

Regular Article - Theoretical Physics

Singlet structure function g₁ at small x and small Q²

¹ Ioffe Physico-Technical Institute, 194021, St. Petersburg, Russia
² Department of Physics and INFN, University Rome III, Via della Vasca Navale 84, 00146, Rome, Italy
³ St. Petersburg Institute of Nuclear Physics, 188300, Gatchina, Russia

^* e-mail: mario.greco@roma3.infn.it

Received: 21 November 2006
Revised: 9 January 2007
Published online: 17 March 2007

Abstract

Explicit expressions for the singlet spin structure function g₁ at small x and small Q² are obtained with a total resummation of the leading logarithmic contributions. It is shown that g₁ practically does not depend on x in this kinematic region. In contrast, it would be interesting to investigate its dependence on the invariant energy 2pq, because g₁, being positive at small 2pq, can turn negative at greater values of this variable. The position of the turning point is sensitive to the ratio of the initial quark and gluon densities, so its experimental detection would enable one to estimate this ratio.