We extract the value of the strong coupling constant alphas from a single-parameter pointlike fit to the photon structure function F2(gamma) at large x and Q2 and from a first five-parameter full (pointlike and hadronic) fit to the complete F2(gamma) data set taken at PETRA, TRISTAN, and LEP. In next-to-leading order and the MSbar renormalization and factorization schemes, we obtain alphas (mZ) = 0.1183 ± 0.0050 (exp.) +0.0029/-0.0028 (theor.) [pointlike] and alphas (mZ) = 0.1198 ± 0.0028 (exp.) +0.0034/-0.0046 (theor.) [pointlike and hadronic]. We demonstrate that the data taken at LEP have reduced the experimental error by about a factor of two, so that a competitive determination of alphas from F2(gamma) is now possible.
Organiser(s): Ariane FREY / EP Division
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