Gamma-Rays Produced in Cosmic-Ray Interactions and the TeV-band Spectrum of RX J1713.7-3946

We employ the Monte Carlo particle collision code DPMJET3.04 to determine the multiplicity spectra of various secondary particles (in addition to \(\pi^0\)'s) with \(\gamma\)'s as the final decay state, that are produced in cosmic-ray (\(p\)'s and \(\alpha\)'s) interactions with the interstellar medium. We derive an easy-to-use \(\gamma\)-ray production matrix for cosmic rays with energies up to about 10 PeV. This \(\gamma\)-ray production matrix is applied to the GeV excess in diffuse Galactic \(\gamma\)-rays observed by EGRET, and we conclude the non-\(\pi^0\) decay components are insufficient to explain the GeV excess, although they have contributed a different spectrum from the \(\pi^0\)-decay component. We also test the hypothesis that the TeV-band \(\gamma\)-ray emission of the shell-type SNR RX J1713.7-3946 observed with HESS is caused by hadronic cosmic rays which are accelerated by a cosmic-ray modified shock. By the \(\chi^2\) statistics, we find a continuously softening spectrum is strongly preferred, in contrast to expectations. A hardening spectrum has about 1% probability to explain the HESS data, but then only if a hard cutoff at 50-100 TeV is imposed on the particle spectrum.