  In this work we report on the effects of short-range correlations upon the
matrix elements of neutrinoless double beta decay. We focus on the calculation
of the matrix elements of the neutrino-mass mode of neutrinoless double beta
decays of 48Ca and 76Ge. The nuclear-structure components of the calculation,
that is the participant nuclear wave functions, have been calculated in the
shell-model scheme for 48Ca and in the proton-neutron quasiparticle
random-phase approximation (pnQRPA) scheme for 76Ge. We compare the traditional
approach of using the Jastrow correlation function with the more complete
scheme of the unitary correlation operator method (UCOM). Our results indicate
that the Jastrow method vastly exaggerates the effects of short-range
correlations on the neutrinoless double beta decay nuclear matrix elements.
