Semi-inclusive large-p_T light hadron pair production as a probe of polarized gluons

We propose a new formula for extracting the polarized gluon distribution $\Delta g$ in the proton from the large--$p_T$ light hadron pair production in deep inelastic semi-inclusive reactions. Though the process dominantly occurs via photon--gluon fusion(PGF) and QCD Compton, we can remove an effect of QCD Compton from the combined cross section of light hadron pair production by using symmetry relation among fragmentation functions and thus, rather clearly extract information of $\Delta g$.