Electromagnetic properties of Majorana neutrinos

The electromagnetic properties of Majorana neutrinos are studied in general terms, with a careful discussion of the difference between the cases of Majorana and Dirac neutrinos. Some peculiarities associated with the Majorana character of the neutrinos are noted; for example, it is shown that for two Majorana neutrinos with the same $\mathrm{CP}$ parity their transition magnetic moment is of the type ${\sigma }_{\mu \nu }{\gamma }_5$ and not ${\sigma }_{\mu \nu }$ in contrast to the situation for the diagonal magnetic moment of Dirac neutrinos (or charged leptons). We also indicate how the electromagnetic form factors in the Majorana case can be obtained from those calculated as if the neutrinos were Dirac particles.