Energy Flows and Jet Production in Tagged e-gamma Events at LEP

TL;DR

This paper investigates the discrepancies between observed energy flow and jet structures in tagged e-gamma events at LEP, highlighting issues with QCD models and proposing analysis of jet configurations to improve understanding of photon structure functions.

Contribution

It introduces a jet-based analysis to identify event classes that poorly match QCD models, aiding in refining photon structure function measurements.

Findings

Discrepancies found between data and QCD models in energy flow distributions.

Jet structure analysis helps identify events with significant model disagreement.

Comparison with pointlike photon model highlights differences in event classes.

Abstract

It has already been shown that the energy flow distributions in tagged events disagree with those predicted by QCD models, generating serious systematic errors in the unfolding of the photon structure function $F_{2}^{\gamma}$. This new analysis uses the jet structure in the hadronic final state to identify the class of events which is in worst agreement with the models. A cone jet finder is used to select events with 0,1 or 2 jets whose transverse energy is greater than 3 GeV. Tagged electrons are detected in the OPAL forward detector at angles between 60 and 120 milliradians. As well as the QCD-based Monte Carlo models, HERWIG and PYTHIA, the simple F2GEN program is used to give a comparison sample of events with purely pointlike photon-quark coupling.