Extraction of Polarized Gluon Distributions from Large-pt Light Hadron Pair Production

We propose a new formula for extracting the polarized gluon distribution from the large-$p_T$ light hadron pair production for semi-inclusive processes in polarized deep inelastic scattering. In general, a large-$p_T$ hadron pair is produced via photon-gluon fusion(PGF) and QCD Compton at the lowest order of QCD. The PGF gives us a direct information on $\mathrm{\Delta }g$ in the nucleon, while QCD Compton becomes background to the signal process for extracting $\mathrm{\Delta }g$. We show that the contribution from this background, i.e. the QCD Compton process, can be removed by using symmetry relation among fragmentation functions and taking an appropriate combination of various light hadron pair production processes, and thus the double spin asymmetry can be described in terms of $\mathrm{\Delta }g\mathrm{/}g$ alone.