Two comments on double beta decay beyond the mass mechanism

Neutrinoless double beta decay is usually discussed in connection with Majorana neutrino masses. However, it is well-known that many different contributions to the decay amplitude could in principle exist. In this talk, I will concentrate on two recent papers on such exotic contributions to 0νββ decay. First the uncertainty in the determination of the short-range (SR) coefficients due to the running of the SR operators at low energies, i.e. (0.1 − 1) GeV, will be discussed. Then, I will turn - once more - to the long-range (LR) part amplitude of 0νββ decay. Here, I discuss the decomposition of all d = 7 ΔL = 2 operators that contribute to LR 0νββ decay. d = 7 operators can lead to models that generate neutrino masses at tree-, 1-loop or 2-loop level. I show one example of a 2-loop model in which the LR amplitude completely dominates over the mass mechanism.Neutrinoless double beta decay is usually discussed in connection with Majorana neutrino masses. However, it is well-known that many different contributions to the decay amplitude could in principle exist. In this talk, I will concentrate on two recent papers on such exotic contributions to 0νββ decay. First the uncertainty in the determination of the short-range (SR) coefficients due to the running of the SR operators at low energies, i.e. (0.1 − 1) GeV, will be discussed. Then, I will turn - once more - to the long-range (LR) part amplitude of 0νββ decay. Here, I discuss the decomposition of all d = 7 ΔL = 2 operators that contribute to LR 0νββ decay. d = 7 operators can lead to models that generate neutrino masses at tree-, 1-loop or 2-loop level. I show one example of a 2-loop model in which the LR amplitude completely dominates over the mass mechanism.