We calculate the complete O(aa:) corrections to the inclusive cross section for hadronic prompt photon production, both for the unpolarized case and for the case of longitudinal polarization for the incoming hadrons. We present analytical expressions for all our results. PACS numbeds): 13.88.+e, 12.38.Bx, 13.85.Qk THE CALCULATION A. Leading-and next-to-leading-order contributionsAt lowest order [ O ( a a , I] two 2 -2 subprocesses are the dominant source for the hadroproduction of prompt photons. These are the annihilation process q q -+ y g and the QCD Compton process qg + yq. The corresponding Feynman diagrams are shown in Fig. 1. A t next-to-leading-order [~( a a i ) ] we encounter a 0556-2821/93/48(7)/3 136(24)/$06.00 48 3136

at colliders. OCR Output the isolation parameters and study the effects the isolation cuts have on the cross section unpolarized case. We demonstrate the good accuracy of our method over a wide range of der, taking into account also the next-to-leading order fragmentation contribution in the for polarized and unpolarized isolated prompt photon production in next-to-leading or We present a simple and accurate analytical method for calculating the cross section Abstract D

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We discuss the transverse momentum distribution for the production of massive lepton-pairs in hadron reactions at fixed target and collider energies within the context of next-to-leading order perturbative quantum chromodynamics. For values of the transverse momentum Q T greater than roughly half the pair mass Q, Q T > Q/2, we show that the differential cross section is dominated by subprocesses initiated by incident gluons. Massive leptonpair differential cross sections are an advantageous source of constraints on the gluon density, free from the experimental and theoretical complications of photon isolation that beset studies of prompt photon production. We compare calculations with data and provide predictions for the differential cross section as a function of Q T in proton-antiproton reactions at center-of-mass energies of 1.8 TeV, and in proton-nucleon reactions at fixed target and LHC energies.