Di-Jet Production in Photon-Photon Collisions at e+e- center-of-mass energies = 161 and 172 GeV

TL;DR

This paper investigates di-jet production in quasi-real photon collisions at LEP energies, comparing experimental measurements of angular distributions, energy profiles, and cross-sections with perturbative QCD predictions and Monte Carlo models.

Contribution

It provides detailed measurements of di-jet production at 161 and 172 GeV and evaluates the accuracy of QCD calculations and Monte Carlo generators with different photon parton distribution parametrizations.

Findings

Measured angular distributions agree with NLO QCD predictions.

Jet energy profiles are consistent with theoretical models.

Monte Carlo generators' predictions vary with different photon parton distributions.

Abstract

Di-jet production is studied in collisions of quasi-real photons radiated by the LEP beams at e+e- centre-of-mass energies 161 and 172 GeV. The jets are reconstructed using a cone jet finding algorithm. The angular distributions of direct and double-resolved processes are measured and compared to the predictions of leading order and next-to-leading order perturbative QCD. The jet energy profiles are also studied. The inclusive two-jet cross-section is measured as a function of transverse energy and rapidity and compared to next-to-leading order perturbative QCD calculations. The inclusive two-jet cross-section as a function of rapidity is compared to the prediction of the leading order Monte Carlo generators PYTHIA and PHOJET. The Monte Carlo predictions are calculated with different parametrisations of the parton distributions of the photon. The influence of the `underlying event' has been studied to reduce the model dependence of the predicted jet cross-sections from the Monte Carlo generators.