Could very high energy gamma rays from the Crab Nebula result from p-p collision?

Abstract

It is generally believed that the very high energy (VHE) gamma rays emitted from the Crab Nebula cannot result from the decay of neutral pions which are produced by the collision between relativistic protons, due to the small hadronic cross section and low column density of the nebula. However, the magnetic field of the Crab Nebula could trap a large amount of relativistic protons from the pulsar with a total energy of up to 1047 erg, because this amount of energy is difficult to release for the same reason. Nevertheless, a small amount of protons will be converted to VHE photons through occasional hadronic collisions which result in steady VHE gamma ray emission with an average power of approximately 4*1034 erg s-1. The authors calculate the proton energy spectrum by using the pulsar evolution model proposed by Ruderman and Cheng (1988).