Ir U LII\VUI'lLJ(( " .xL"rrrrl'lrr+ a,,u J " rr;ltjou"Jy t Inslitute of Nuclear Physics, NCSR Demohtos, GR-15310 Aghia Paraskwi. Greea % ?heoretical Division, Los Alamas National Laboratory, Los Alamas, NM 87545, USA 5 Physirs Depanment, I h e University of loannina, GR-45338 loannina, Greece

I h e structure of lhe 3 3 < Z < 44 and N = 49,48 nuclei is examined by mnsidering the doubly closed 'ESn as a mre and placing proton and neulmn holes in the Og9/2, lp1/2, lp3/2 and Ihe OE/2 orbilals. The effective intenclion tor this model space has been derived by introducing second-order corrections to the Sussex matrix elements, while the one-hole energies have k e n deduced bj a least-squares fit to the ObseNed levels. I1 is found that agreement with experimenl can be improved b, introducing three parameten which madify Ihe strength of some T = 0 matrix elements.' R e results of the calculalion are found, generally, to be in satisfacloty agreement with experiment for most nuclei examined. However. as in the case of Ihe N = 50 nuclei, lhere are indications Ihat configurations oulside lhe model space begin to influence the lau-lying spectra of the N = 49, 48 nuclei as the number of valence holes increases.

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The nuclear matrix elements for the Ge~' Se, ' Se~Kr, ' Se~' Kr, and ' Kr~' Sr double p decay were calculated in a shell-model space consisting of the Og9/2 1P,&2, lp3&2, and Ofsqz orbitals for both protons and neutrons, and using an effective interaction that contained secondorder corrections. For light intermediate neutrinos our results are in agreement with the previously available Los Alamos matrix elements. We have, however, obtained nuclear matrix elements relevant for intermediate heavy neutrinos, Higgs bosons, and supersymmetric particles. Using these matrix elements and the available experimental limits for neutrinoless double p decay, we obtained the following mass limits:~(m, )~&1.1 eV, ((1/MN)) '&1.0X10' GeV, m &740 GeV, and m, & 360 GeV for the light left-handed and heavy right-handed neutrinos, the squark, and the selectron, respectively. We also obtained the limits~g~&4)&10 ' and r)&1.3x10 for the majoron neutrino coupling and the admixture of right-handed currents, respectively.

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