It is widely believe that galactic cosmic rays are originated in supernovaremnants (SNRs) where they are accelerated by diffusive shock accelerationprocess at supernova blast waves driven by expanding SNRs. In recenttheoretical developments of the diffusive shock acceleration theory in SNRs,protons are expected to accelerate in SNRs at least up to the knee energy. IfSNRs are true generator of cosmic rays, they should accelerate not only protonsbut also heavier nuclei with right proportion and the maximum energy of heaviernuclei should be atomic mass (Z) times that of protons. In this work weinvestigate the implications of acceleration of heavier nuclei in SNRs onenergetic gamma rays those are produced in hadronic interaction of cosmic rayswith ambient matter. Our findings suggest that the energy conversion efficiencyhas to be nearly double for the mixed cosmic ray composition instead of pureprotons to explain the observation and secondly the gamma ray flux above fewtens of TeV would be significantly higher if cosmic rays particles can attainenergies Z times of the knee energy in lieu of 200 TeV, as suggested earlierfor non-amplified magnetic fields. The two stated maximum energy paradigm willbe discriminated in future by the upcoming gamma ray experiments like CherenkovTelescope array (CTA).
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