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We report results on inclusive direct photon (); 0 , and production in both pp and pp interactions at p s = 2 4 : 3 GeV in the transverse momentum range 4:1 p T 7:7 GeV/c and rapidity range 0:1 y 0:9. The data were collected between 1988 and 1990 by the UA6 experiment at CERN, which employed an internal H 2 gas jet target in the S ppS collider. The inclusive direct photon cross sections and the cross section dierence (pp) (pp) expressed as functions of p T () are compared with next-to-leading order QCD predictions.

Direct photon cross sections obtained in pp and pp collisions at p s = 2 4 : 3 GeV at the CERN SPS, are used in a next-to-leading order QCD analysis. From the cross-section dierence (p p ! X) (pp ! X), and quark distributions measured in deep inelastic scattering, a determination of the strong coupling constant, s , is performed via a measurement o f 4 MS. This rst measurement o f 4 MS using direct photon data yields a value 4 MS = 235 79 (stat:

Direct photon production cross sections obtained in high statisticspp and pp collisions at √ s = 24.3 GeV at the CERN SPS are used in a next-to-leading order QCD analysis. From the cross section difference σ(pp → γX) − σ(pp → γX) and quark distributions measured in deep inelastic scattering, a determination of the strong coupling constant, α s , is performed via a measurement of Λ (4) MS. This measurement yields a value Λ (4) MS = 210 ± 22 (stat.) ± 44 (syst.) +105 −36 (theo.) MeV. The corresponding value of α s expressed at M 2 Z is α s (M 2 Z) = 0.1112 ± 0.0016 (stat.) ± 0.0033 (syst.) +0.0077 −0.0034 (theo.).

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