The impact of excited neutrinos on $\nu \bar{\nu}\to \gamma\gamma$   process
  We examine the effect of excited neutrinos on the annihilation of relic neutrinos with ultra high energy cosmic neutrinos for the $\nu \bar{\nu}\to \gamma\gamma$ process. The contribution of the excited neutrinos to the neutrino-photon decoupling temperature are calculated. We see that photon-neutrino decoupling temperature can be significantly reduced below the obtained value of the Standard Model with the impact of excited neutrinos. 
S. C. Inan and M. Koksal
hep-ph astro-ph.CO