Tuning MC Models to Fit DIS e-gamma Scattering Events

TL;DR

This paper evaluates and tunes Monte Carlo models for deep inelastic scattering e-gamma events to better match experimental data, highlighting the importance of accurate modeling for extracting photon structure functions.

Contribution

It introduces tuning procedures for Herwig, Pythia, and Ariadne models to improve their agreement with observed data in DIS e-gamma scattering.

Findings

Models underestimate high-p_T contributions at low-x.

Tuning improves model-data agreement.

Understanding physics is crucial for accurate photon structure functions.

Abstract

Monte Carlo models of DIS e-gamma scattering must describe hard emissions as well as the soft and collinear limits. Comparison with the observed experimental hadronic energy flow has shown that various models underestimate the high-p_T contribution, in particular at low-x. We have attempted to tune the Herwig, Pythia and Ariadne models to improve the agreement with the data, and to understand the physical implications of the changes required. Unless the physics of these processes is understood it will not be possible to unfold the photon structure functions F_2^\gamma from the e^+e^- data without large model dependent systematic errors.