for leptons in the SM is purely left-handed, it picks out the $m_{\nu}$ part, i.e., the amplitude of the (standard) mass mechanism of [$0\nu\beta\beta$ ]{}is proportional to $m_{\nu}$. Clearly, then not all $\epsilon_{\alpha}^{\beta}$ can be constrained from [$0\nu\beta\beta$ ]{}decay, due to the absence of a lower bound on $m_{\nu}$. On the other hand, if the new physics in diagram (b) generates a right-chiral lepton interaction $(j_{V+A}, j_{S+P}, j_{T_{R}})$, the ${q\!\!\!/}$-term in the neutrino propagator will enter the amplitude. The size of the 3-momentum $|{\vec q}|$ can be estimated from the typical inter-nucleon distance of two neutrons in the nucleus to be of the order of 100 MeV. Therefore, the amplitudes with ${q\!\!\!/}$-terms are highly enhanced in comparison with those with the $m_{\nu}$-term.[^11] For this reason, the coefficients $\epsilon_{\alpha}^{\beta}$ with right-chiral leptonic interactions, are heavily constrained by [$0\nu\beta\beta$ ]{}decay. The hadronic and leptonic currents are best defined as currents of definite chirality (as defined at Eq. ) to take care of this fact.

In Table \[Tab:LimitsLong\] we give the updated bounds for all $\epsilon_{\alpha}^{\beta}$, which are taken from [@Deppisch:2012nb]. Note that the index $\beta$ for the leptonic current in the table takes neutrino interactions with the chirality $R$ in the exotic 