Strong dineutron correlation inHe8andC18

Abstract

We study the spatial structure of four valence neutrons in the ground state of 8 He and 18 C nuclei using a core+4n model. For this purpose, we employ a density-dependent contact interaction among the valence neutrons, and solve the five-body Hamiltonian in the Hartree-Fock-Bogoliubov (HFB) approximation. We show that two neutrons with the coupled spin of S=0 exhibit a strong dineutron correlation around the surface of these nuclei, whereas the correlation between the two dineutrons is much weaker. Our calculation indicates that the probability of the (1p 3/2 ) 4 and [(1p 3/2 ) 2 (p 1/2 ) 2 ] configurations in the ground state wave function of 8 He nucleus is 34.9% and 23.7%, respectively. This is consistent with the recent experimental finding with the 8 He(p, t) 6 He reaction, that is, the ground state wave function of 8 He deviates significantly from the pure (1p 3/2 ) 4 structure.

BCS-BEC crossover in symmetric nuclear matter at finite temperature: Pairing fluctuation and pseudogap

“…At the same time, the chemical potential changes its sign at a certain density and finally approaches one-half of the deuteron binding energy at the low-density limit. Recently, a similar situation was also studied for the neutron-neutron (nn) pairs in the 1 S 0 channel [14][15][16][17][18][19][20][21][22][23][24][25]. It was found that in certain (low) density regions the nn pairs can be strongly correlated.…”

Halo nuclei, stepping stones across the drip-lines

“…The momentum profile function shown in figure 14 first of all confirms the assignment, as the major part of the 7 He spectrum seems to arise from = 1 neutrons in 8 He. Interestingly enough, at low relative energies a deviation pointing to the appearance of = 0 strength is found with a weight of 4.3(5)% in the 8 He ground-state wave function, which is also expected theoretically [100] with a weight of 7.8 % for the (1s 1/2 ) 2 (0p 3/2 ) 2 configuration. This has been seen before-while analysing the relative energy spectrum of 5 He [71]-in 6 He.…”

“…A direct observation of the final state would be desirable, because the interpretation of the existing data suffers from uncertainties induced by unwanted background contributions that could be avoided with a more selective correlation analysis. Theory predicts that the five-body continuum can be treated with three-body methods [100,101] as strong di-neutron correlations should be present in the system. This is also predicted for the seed nucleus 8 He, so it would be interesting to populate the 7 H system with proton removal from 8 He and compare this to α-removal from 11 Li.…”

Two-neutron correlations in microscopic wave functions of6He,8He, and12C

“…nn correlations have been intensively investigated for asymmetric nuclear matter [17][18][19][20][21][22][23][24], and are discussed also in light neutron-rich nuclei such as 8 He [25][26][27][28][29][30] and in medium-heavy neutron-rich nuclei [31,32]. These studies suggest that the nn correlations play an enhanced role at the nuclear surface of finite nuclei and in model studies of infinite neutron matter at low density (weak interactions turned off).…”