Production of Neutrinos and Secondary Electrons in Cosmic Sources

TL;DR

This paper models secondary lepton production from cosmic-ray interactions using Monte Carlo simulations, applies it to supernova remnants, and predicts neutrino detection prospects to test hadronic cosmic-ray origins.

Contribution

It introduces detailed production matrices for secondary particles from cosmic-ray interactions, including resonances, up to 10 PeV energies, and applies them to astrophysical observations and neutrino detection predictions.

Findings

Magnetic fields in SNRs are unlikely to be large over extensive regions.

The cosmic-ray spectrum in the 0.1-100 GeV range must be unusually hard if high magnetic fields are present.

Neutrino detection over 5-10 years can test the hadronic origin of TeV gamma-ray sources.

Abstract

We study the individual contribution to secondary lepton production in hadronic interactions of cosmic rays (CRs) including resonances and heavier secondaries. For this purpose we use the same ethodology discussed earlier \cite{Huang07}, namely the Monte Carlo particle collision code DPMJET3.04 to determine the multiplicity spectra of various secondary particles with leptons as the final decay states, that result from inelastic collisions of cosmic-ray protons and Helium nuclei with the interstellar medium of standard composition. By combining the simulation results with parametric models for secondary particle (with resonances included) for incident cosmic-ray energies below a few GeV, where DPMJET appears unreliable, we thus derive production matrices for all stable secondary particles in cosmic-ray interactions with energies up to about 10 PeV. We apply the production matrices to calculate the radio synchrotron radiation of secondary electrons in a young shell-type SNR, RX J1713.7-3946, which is a measure of the age, the spectral index of hadronic cosmic rays, and most importantly the magnetic field strength. We find that the multi-mG fields recently invoked to explain the X-ray flux variations are unlikely to extend over a large fraction of the radio-emitting region, otherwise the spectrum of hadronic cosmic rays in the energy window 0.1-100 GeV must be unusually hard. We also use the production matrices to calculate the muon event rate in an IceCube-like detector that are induced by muon neutrinos from high-energy $\gamma$-ray sources such as RX J1713.7-3946, Vela Jr. and MGRO J2019+37. At muon energies of a few TeV, or in other word, about 10 TeV neutrino energy, an accumulation of data over about five to ten years would allow testing the hadronic origin of TeV $\gamma$-rays.