RADGEN 1.0. Monte Carlo Generator for Radiative Events in DIS on Polarized and Unpolarized Targets

TL;DR

RADGEN 1.0 provides a dedicated Monte Carlo framework to simulate DIS events with real photon radiation for both polarized and unpolarized targets. It combines two established approaches (MT and Bardin–Shumeiko) and two code bases (FERRAD and POLRAD) to compute radiative corrections and generate radiative tails across elastic, quasielastic, and inelastic channels. The authors perform analytical cross-checks and numerical validations, including Δ-independence considerations and HERMES-like kinematics, demonstrating consistency between the polarized and unpolarized implementations and the reliability of the RC factors. The tool is integrated into the HERMES MC and is intended to improve the fidelity of radiative-event modelling in DIS analyses and polarization observables.

Abstract

A new Monte-Carlo generator including real radiated photons in DIS on polarized and unpolarized targets is presented. Analytical and numerical tests are performed and discussed in details.

Figures (4)

• Figure 1: Feynman diagrams contributing to the Born and the radiative correction cross sections in lepton-nucleus scattering.
• Figure 2: The weighted $x_{true}$ and $Q^2_{true}$ distributions as generated by FERRAD (histogram) and POLRAD with polarization part switched off (points) a), b); and by POLRAD with parallel (histogram) and antiparallel (points) spin configurations c), d).
• Figure 3: The distribution of the radiation angles $\theta_{\gamma}$ a) and $\phi_{\gamma}$ b) and of the energy c) of the radiated photon for $x=0.1$ and $y=0.8$. The two-dimensional distribution d) shows $\theta_{\gamma}$ vs $\phi_{\gamma}$.
• Figure 4: The typical distribution of the radiative correction factor.