Inclusive production of direct photons in 200-GeV/c collisions

The authors have measured the inclusive production of direct photons in the transverse momentum (p/sub T/) range 2.1--5.0 GeV/c in 200-GeV/c collisions of protons and ..pi../sup +/ mesons on a carbon target. A significant yield of direct photons was observed for p/sub T/>2.5 GeV/c. The invariant cross section for direct-photon production, when compared with measurements from the CERN intersecting storage rings, can be expressed in terms of p/sub T/ and x/sub T/ = 2p/sub T/root-bars as (42 +- 14)(1-x/sub T/)/sup 8.1plus-or-minus1.0/p /sub T//sup -6.6plus-or-minus0.3/..mu..b/GeV/sup 2/ for the c.m. energy range from ..sqrt..s = 19.4 to 63 GeV, and for the x/sub T/ range from 0.2 to 0.5.