EleCa: a Monte Carlo code for the propagation of extragalactic photons at ultra-high energy

TL;DR

EleCa is a new Monte Carlo simulation tool designed to model the propagation and electromagnetic cascading of ultra-high energy photons and electrons across extragalactic space, aiding in interpreting cosmic ray observations.

Contribution

The paper introduces EleCa, a novel Monte Carlo code specifically developed for simulating electromagnetic cascades initiated by UHE photons and electrons in extragalactic environments.

Findings

EleCa effectively models UHE photon propagation and cascades.

The code helps estimate the observable UHE photon flux at Earth.

Simulations inform constraints on astrophysical models of UHECRs.

Abstract

Ultra high energy photons play an important role as an independent probe of the photo-pion production mechanism by UHE cosmic rays. Their observation, or non-observation, may constrain astrophysical scenarios for the origin of UHECRs and help to understand the nature of the flux suppression observed by several experiments at energies above 10$^{19.5}$ eV. Whereas the interaction length of UHE photons above 10$^{17}$ eV is only of a few hundred kpc up to tenths of Mpc, photons can interact with the extragalactic background radiation leading to the development of electromagnetic cascades which affect the fluxes of photons observed at Earth. The interpretation of the current experimental results rely on the simulations of the UHE photon propagation. In this contribution, we present the novel Monte Carlo code "EleCa" to simulate the \emph{Ele}ctromagnetic \emph{Ca}scading initiated by high-energy photons and electrons. The distance within which we expect to observe UHE photons is discussed and the flux of GZK photons at Earth is investigated in several astrophysical scenarios.