Neutrino mass from bremsstrahlung endpoint in coherent scattering on nuclei

Abstract

We calculate the coherent bremsstrahlung process $\nu +\mathcal{N}\to \mathcal{N}+\nu +\gamma$ off a nucleus $\mathcal{N}$ with the aim of revealing the neutrino mass via the photon endpoint spectrum. Unfortunately, the large required power of a monochromatic neutrino source and/or large detector mass make it difficult to compete with traditional electron-spectrum endpoint measurements in nuclear $\beta$ decay. Our neutral-current process distinguishes between Dirac and Majorana neutrinos, but the change of the photon spectrum is of the order of $m_{\nu }/E_{\nu }$ and thus very small, despite the final-state neutrino coming to rest at the photon endpoint. So the "Dirac-Majorana confusion theorem" remains intact even if $E_{\nu }\gg m_{\nu }$ applies only for the initial state.

Comments: 5 pages, 2 figures. v2: matches published version