QCD predictions for spin dependent photonic structure function $g_1^{\gamma }(x,Q^2)$ in the low x region of future linear colliders

Abstract

Spin dependent structure function $g_1^{\gamma }(x,Q^2)$ of the polarised photon is analysed within the formalism based upon the unintegrated spin dependent parton distributions incorporating the LO Altarelli-Parisi evolution and the double $l{n}^2(1/x)$ resummation at low values of Bjorken parameter x. We analyse the effects of the double $l{n}^2(1/x)$ resummation on the behaviour of $g_1^{\gamma }(x,Q^2)$ in the low x region which may be accessible in future linear $e^{+}{e}^{-}$ and $e\gamma$ colliders. Sensitivity of the predictions on the possible nonperturbative gluon content of the polarised photons is analysed. Predictions for spin dependent gluon distribution $\Delta g^{\gamma }(x,Q^2)$ are also given.

Comments: revised version, 19 pages, latex, 8 figures. To appear in Phys. Rev. D