Efficient Cosmic Ray Ion Production in Young Supernova Remnants
  The strong shocks in young supernova remnants (SNRs) should accelerate cosmic rays (CRs) and no doubt exists that relativistic electrons are produced in SNRs. However, direct evidence that SNRs produce CR nuclei depends on seeing an unambiguous pion-decay feature and this has not yet been obtained. Nevertheless, the lack of an observed pion-decay feature does not necessarily mean that CR ions are not abundantly produced since ions do not radiate efficiently. If CR ions are produced efficiently by diffusive shock acceleration (DSA), their presence will modify the hydrodynamics of the SNR and produce morphological effects which can be clearly seen in radiation produced by electrons. 
Donald C. Ellison and Gamil Cassam-Chenai