Isospin dependence of NN correlations and the reduction of the single-particle strength in atomic nuclei

The atomic nucleus consists of strongly interacting nucleons. It is noteworthy that for such strongly interacting quantum system the independent-particle model is proven to be a valid approximation and has provided the framework to explain many properties of nuclei. However, correlations between the nucleons, both of short- and long-range nature, modify the mean-field approximation and dilute the pure independent-particle picture. Notably, these correlations are thought to be the reason for the quenching of spectroscopic factors observed in (e,e’p), (p,2p) and transfer reactions [1].

Here we propose a phenomenological approach to examine the role of NN short- and long-range correlations and their evolution in asymmetric systems. In particular, we show that the recently observed [2] increase of the high-momentum component of the proton momentum density in a neutron-rich nucleus correlates nicely with the reduced proton occupancies for states below or near the Fermi level [3,4], as a function of the asymmetry (N-Z)/A.

[1] Dickhoff and Barbieri, PPNP 52 (2004) 377

[2] Duer et al., Nature, In-Print (2018) 

[3] Kramer, Blok and Lapikas, NPA 679 (2001) 267

[4] Atar et al., PRL 120 (2018) 052501