DOI 10.1007/s100529800958
Final state photon production at LEP
A. Gehrmann-De Ridder1 - E.W.N. Glover2
1 DESY, Theory Group, D-22603 Hamburg, Germany
2 Department of Physics, University of Durham, Durham DH1 3LE, England
Received: 9 June 1998 / Published online: 21 August 1998
Abstract
We present a detailed study of photon production
in hadronic events in electron-positron
annihilation at LEP energies.
We show that estimates of the inclusive photon spectrum using
the quark-to-photon fragmentation function
determined using the
ALEPH `photon' + 1 jet data agree well with the observations of the OPAL collaboration.
This agreement shows that the photon fragmentation function
determined in this way can be used for inclusive observables.
We also compare next-to-leading order and beyond leading
logarithm predictions obtained using the numerically resummed
solutions of the fragmentation function evolution equation of
Bourhis, Fontannaz and Guillet and Glück, Reya and Vogt with the data.
Moreover, in order to check the general behaviour of the
fragmentation function, we consider an analytic series expansion
in the strong coupling.
We find that the parameterizations are inaccurate at large x values.
While the OPAL data is in broad agreement with estimates
based on any of these approaches,
the ALEPH data prefers the resummed BFG parameterization.
Finally, there is some ambiguity as to whether the fragmentation function
is treated as 
or 
. We show that at present this ambiguity affects mainly the prediction
for the `photon' + 1 jet rate at large z.
Copyright Springer-Verlag
