Associated Production of Charm and a Hard Photon.pdf

a r X i v : h e p - p h / 9 6 0 4 4 4 7 v 1 3 0 A p r 1 9 9 6 ANL-HEP-CP-96-33 May 1, 1996 ASSOCIATED PRODUCTION OF CHARM AND A HARD PHOTON B. Baileya, E. L. Bergerb and L. E. Gordonb aPhysics Department, Eckerd College, St. Petersburg, FL 33711, U.S.A. bHigh Energy Physics Division, Argonne National Laboratory, Argonne, IL 60439, U.S.A. ABSTRACT The two particle inclusive cross section for the reaction p + p? → γ + c + X is studied in perturbative quantum chromodynamics at order O(α2s), for large values of the transverse momentum of the prompt photon and charm quark. Two different techniques are used in performing the phase-space integrals; the first is purely analyti- cal, and the second is a combination of analytic and Monte Carlo integration methods. The second, more versatile technique facili- tates imposition of photon isolation restrictions and other selections of relevance in experiments. Differential distributions are provided for various observables, and a comparison is made with preliminary data from the CDF collaboration. Invited talk presented by L. E. Gordon at the XXXI st Rencontres de Moriond, ‘QCD and High Energy Hadronic Interactions’ March 23-30, 1996, Les Arcs, France 1. Introduction The observation of a photon carring a large transverse momentum, pT , among the final state products of a high energy hadronic reaction has long been regarded as a powerful tool for gathering information about the short distance dynamics of these reactions, primarily because photons couple directly to quarks via the point-like electromagnetic interaction. Single prompt photon production has been studied extensively, both theoretically and ex- perimentally, and has provided useful information about hadronic structure, in particular the gluon structure function of the proton. Data are beginning to appear from the study of the production of a prompt photon (γ) in association with a heavy quark whose transverse momentum balances a substantial portion of that of the