New properties of the high-momentum distribution of nucleons in asymmetric nuclei

Based on the recent experimental observations of the dominance of tensor interaction in the $\sim$250–600 MeV/c momentum range of nucleons in nuclei, the existence of two new properties for high-momentum distribution of nucleons in asymmetric nuclei is suggested. The first property is the approximate scaling relation between proton and neutron high-momentum distributions weighted by their relative fractions in the nucleus. The second property is the inverse proportionality of the strength of the high-momentum distribution of protons and neutrons to the same relative fractions. Based on these two properties the high-momentum distribution function for asymmetric nuclei has been modeled and demonstrated so that it describes reasonably well the high-momentum characteristics of light nuclei. However, the most surprising result is obtained for neutron rich nuclei with large $A$, for which a substantial relative abundance of high-momentum protons as compared to neutrons is predicted. For example, the model predicts that in Au the relative fraction of protons with momenta above $k_F\sim 260$ MeV/c is $50\%$ more than that of neutrons. Such a situation may have many implications for different observations in nuclear physics related to the properties of a proton in neutron-rich nuclei.

Figure 1

(a) The momentum distributions of a proton and neutron weighted by $x_p$ and $x_n$, respectively. The doted lines represent the prediction for the momentum distribution according to Eq. (5). (b) The $x_{p/n}$ weighted ratio of neutron to proton momentum distributions. See the text for details.