INCLUSIVE HADRON-PRODUCTION IN PHOTON-PHOTON COLLISIONS AT NEXT-TO-LEADING ORDER

We study inclusive charged-hadron production in collisions of quasirea l photons at next-to-leading order (NLO) in the QCD-improved parton mo del, using fragmentation functions recently extracted from PEP and LEP 1 data of e(+)e(-) annihilation. We consistently superimpose the direc t (DD), single-resolved (DR), and double-resolved (RR) gamma gamma cha nnels. We consider photon spectra generated by electromagnetic bremsst rahlung and/or beamstrahlung off colliding e(+) and e(-) beams as well as those which result from backscattering of laser light off such bea ms. First, we reconsider existing single-tag data taken by TASSO at PE TRA acid by MARK II at PEP (with e(+)e(-) energy root s approximate to 30 GeV) and confront them with our NLO calculations imposing the resp ective experimental cuts. We also make comparisons with the neutral-ka on to charged-hadron ratio measured by MARK II. Then, we present NLO p redictions for LEP2, a next-generation e(+)e(-) linear collider (NLC) in the TESLA design with root s=500 GeV, and a Compton collider obtain ed by converting a 500-GeV NLC. We analyze transverse-momentum and rap idity spectra with regard to the scale dependence, the interplay of th e DD, DR, and RR components, the sensitivity to the gluon density insi de the resolved photon, and the influence of gluon fragmentation. It t urns out that the inclusive measurement of small-p(T) hadrons at a Com pton collider would greatly constrain the gluon density of the photon and the gluon fragmentation function.