Nuclear enhancement factor in calculation of Galactic diffuse gamma-rays: A new estimate with DPMJET-3

A new calculation of nuclear enhancement factor, used in estimation of Galactic diffuse gamma-ray flux from proton–proton interaction in order to take account of heavy nuclei included in cosmic-rays and interstellar matter, is presented by use of a Monte Carlo simulator, DPMJET-3. A new value of 1.8–2.0 in the energy range of 6–1000 GeV/nucleon, slightly increasing with kinetic energy of projectile cosmic-rays, is about 20% larger than previous estimates.