Investigation of the string effect using final state photons

The string effect in QCD is investigated using data from the OPAL detector at LEP. By comparing the charged particle flow in three-jet multihadronic events with that in events with two jets and a hard isolated photon, the sensitivity to particular models is reduced. A comparison with various Monte Carlo models is presented. The difference in particle flows in the interquark region is found to be well reproduced by a leading order calculation of soft gluon emission, in the spirit of the Local Parton Hadron Duality hypothesis.