Pairing correlations. Part 2: Microscopic analysis of odd-even mass staggering in nuclei

The odd-even mass staggering in nuclei is analyzed in the context of self-consistent mean-field calculations, for spherical as well as for deformed nuclei. For these nuclei, the respective merits of the energy differences $\Delta^{(3)}$ and $\Delta^{(5)}$ to extract both the pairing gap and the time-reversal symmetry breaking effect at the same time are extensively discussed. The usual mass formula $\Delta^{(3)}$, is shown to contain additional mean-field contributions when realistic pairing is used in the calculation. A simple tool is proposed in order to remove time-reversal symmetry breaking effects from $\Delta^{(5)}$. Extended comparisons with the odd-even mass staggering obtained in the zero pairing limit (schematic model and self-consistent calculations) show the non-perturbative contribution of pairing correlations on this observable. PACS: 21.10Dr; 21.10.Hw; 21.30.-x. Keywords: Mean-field theories; Pairing correlations; Odd-even mass staggering;