P. Abreu et al., STUDY OF HARD SCATTERING PROCESSES IN MULTIHADRON PRODUCTION FROM GAMMA-GAMMA COLLISIONS AT LEP, Zeitschrift fur Physik. C, Particles and fields, 62(3), 1994, pp. 357-365
The production of multihadronic states in gammagamma collisions at LEP
has been studied with the DELPHI detector. The analyzed data correspo
nd to an integrated luminosity of about 32 pb-1, collected in the LEP
runs of 1990-1992. Minimum bias data and a sample of events with jets
at high p(T) have been selected under the requirement that no scattere
d electron or positron is observed. The two data sets have been compar
ed to Monte Carlo. predictions. The non-perturbative contribution desc
ribed by the vector meson dominance Model and direct qqBAR production
from pointlike photons described by the quark parton model were found
to be insufficient to reproduce the data. It has been necessary to inc
lude a third interaction component, which is due to perturbative hard
scattering of the partonic constituents of the photon. Several paramet
risations of the quark and gluon densities of the photon have been tes
ted. The interplay with the cut in jet transverse momentum, which is n
ecessary for the separation of the perturbative and non-perturbative r
egions, is discussed. The data favour parametrisations with rather sof
t partonic content of the photon.