Additional nucleon current contributions to neutrinoless doubleβdecay

We have examined the importance of momentum-dependent-induced nucleon currents such as weak-magnetism and pseudoscalar couplings to the amplitude of neutrinoless double beta decay $(0\mathrm{}\nu \beta \beta$ decay) in the mechanisms of light and heavy Majorana neutrino, as well as in that of Majoron emission. Such effects are expected to occur in all nuclear models in the direction of reducing the light neutrino matrix elements by about $30\%.$ To test this we have performed a calculation of the nuclear matrix elements of the experimentally interesting nuclei $A=76,\hspace{0.5em}82,\hspace{0.5em}96,\hspace{0.5em}100,\hspace{0.5em}116,\hspace{0.5em}128,\hspace{0.5em}130,\hspace{0.5em}136,$ and 150 within the proton-neutron renormalized quasiparticle random-phase approximation. We have found that indeed such corrections vary somewhat from nucleus to nucleus, but in all cases they are greater than $25\%.$ In the case of a heavy neutrino the effect is much larger (up to a factor of 6). Combining our results with the best presently available experimental limits on the half-life of the $0\nu \beta \beta$ decay, we have extracted new limits on the effective neutrino mass (light and heavy) and the effective Majoron coupling constant.