Spatial particle correlations in 6He and 8He Pu MEI

GANIL Guest House - Monday 19th September - 14h00

Spatial two-particle correlations are derived that display the probability distribution
of two identical nucleons in a shell as a function of their relative distance
and their distance from the centre of the nucleus. It is shown that a two-nucleon
state in the p shell with total orbital angular momentum L = 0 and total spin
S = 0 contains a di-neutron and a cigar-like component with equal probability.
This result can also be proven analytically with the use of angular correlation
functions. Scattering of the nucleons from the p shell to higher shells leads to
the enhancement of the di-neutron configuration. An application to 6He is presented
which shows that the probability of the di-neutron configuration in the
ground state is of the order of 60%.
The geometry of configurations of identical particles in a shell is then extended
from two to four particles. Particular attention is paid again to the p shell, which
is of relevance for the nucleus 8He. Expressions are given for the angular probability
density in terms of the six angles between pairs of position vectors of
the particles. The analysis of the p shell reveals the existence of two classes
of favoured four-particle geometries, which have been called ‘great-circle’ and
‘tetrahedral’, with three members each. The transition from one class to the
other is governed by the nuclear dynamics and depends on the conflicting tendencies
of the short-range nuclear interaction versus the spin-orbit splitting