Strong Coupling Constant from the Photon Structure Function

<!--HTML-->We extract the value of the strong coupling constant <i>alpha_s</i> from a single-parameter pointlike fit to the photon structure function <i>F₂(gamma)</i> at large <i>x</i> and <i>Q²</i> and from a first five-parameter full (pointlike and hadronic) fit to the complete <i>F₂(gamma)</i> data set taken at PETRA, TRISTAN, and LEP. In next-to-leading order and the <i>MSbar</i> renormalization and factorization schemes, we obtain <i>alpha_s (m_Z)</i> = 0.1183 ± 0.0050 (exp.) ^+0.0029/_-0.0028 (theor.) [pointlike] and <i>alpha_s (m_Z)</i> = 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 <i>alpha_s</i> from <i>F₂(gamma)</i> is now possible.<BR><BR><I>Organiser(s): Ariane FREY / EP Division</I><BR><BR><I>Note: Tea and coffee will be served at 15:00 hrs. Please note unusual day and place.</I>