Study of the pairing force in nuclei

This work is dedicated to the study of the pairing potential for the nuclei in the stability valley and for the super-deformed isotope groups. The purpose is to propose a pairing force that could be considered as a reference in order to explore the exotic nuclei on safer basis. The domain on which the potential parameters have been studied is defined by: ecut = 5 ± 2 MeV, dcut = 0.5 MeV, V0 = 1000 ± 200 MeV for 1 cut, V0 = 1200 ± 200 MeV for 2 cuts. As for the choice of nuclei 3 crosses in the (N,Z) plane have been defined, each centered around a doubly magic isotope: N=Z=28, N=Z=50 and N=Z=82. The results are presented for the nuclei around Ni56. It is shown that the best choice for potential parameters is V0 = 1000 MeV and ecut = 4 MeV, but the pairing effect remains underestimated for the nuclei between N=28 and N=32. For the nuclei N ≤ 26 or N ≥ 38 the disagreement is more important and it requires more than an optimization of the pairing effect for being corrected, the causes of the discrepancy seem to be an insufficient mean field and a lack of accuracy in the Hartree-Fock part. (A.C.)