I've a question regarding the interpretation of the neutrinos in neutrinoless double beta decay:
The basic issue that I have is with papers that regard the decay as a neutrino-neutrino annihilation (as the neutrino is a Majorana particle in this case). The reason is that it can't be classical annihilation because we'd get no end-product (and therefore a loss of energy) like in electron-positron annihilation.
Now you could say "they are virtual particles so they don't lie on their mass shell", but wouldn't it then be better to avoid this annihilation interpretation completely? Another interpretation could be nucleon-neutrino absorption and isn't that a better one? This process could at least in principal (neutrino-up -> W- -> electron-down) also happen with a "lone", real neutrino.
So what I want to say is that the annihilation interpretation is at least controversial, right (apart from the perturbative character of virtual particles)?