The Kinematics of Deep Inelastic Scattering in the Presence of Initial State Radiation

TL;DR

This paper investigates how initial state radiation affects the kinematic reconstruction in deep inelastic scattering experiments, proposing methods to measure and correct for ISR effects at HERA.

Contribution

It introduces techniques to determine ISR photon energy and correct kinematic variables, improving accuracy in deep inelastic scattering measurements.

Findings

ISR causes significant shifts in reconstructed variables

Measuring three out of four variables allows ISR photon energy determination

Methods are demonstrated for HERA experiments

Abstract

Initial state radiation (ISR) in deep inelastic scattering of charged leptons on nucleons can lead to substantial shifts in the reconstruction of $Q^2$ and the scaling variables $x$ and $y$. By measuring at least three out of the four variables: energy and production angle of the lepton and the hadron system, the energy of the ISR photon emitted under zero degrees can be determined. The ISR effect is illustrated for experimentation at HERA with different methods of kinematic reconstruction.