A new determination of alpha(s) using direct photon production cross sections in pp and (p)over-bar-p collisions at root s=24.3GeV

Direct photon production cross sections obtained in high statistics (p)over -bar-p and pp collisions at root s = 24.3 GeV at the CERN SPS are used in a next-to-leading order QCD analysis. From the cross section difference sigm a((p)over-bar-p --> gamma X) - sigma(pp --> gamma X) and quark distribution s measured in deep inelastic scattering, a determination of the strong coup ling constant, alpha(s), is performed via a measurement of Lambda((MS)over- bar)((4)). This measurements yields a value Lambda((MS)over-bar)((4)) = 210 +/- 22(stat.) +/- 44(syst.) (+105)(-36) (theo.) MeV. The corresponding val ue of alpha(s) expressed at M-Z(2) is alpha(s)(M-Z(2)) = 0.1112 +/- 0.0016( stat.) +/- 0.0033(syst.)(-0.0034)(+0.0077)(theo.). (C) 1999 Elsevier Scienc e B.V. All rights reserved.