Manifestations of a dineutron cluster in elastic α 6He scattering

Mechanisms of sequential particle transfer and characteristics of light neutron-excess and oriented nuclei

“…After substituting (37) into (36), an expression for the matrix element assumes the form of the matrix element convolution for two pole mechanisms, appearing upon cutting up the whole quadrangle dia gram ( Fig. 6) into two independent position spaces: r (for the upper pole diagram) and r' (for the lower one): (38) where correspond to the matrix elements of the lower (upper) part of a whole diagram with replacing the distorted waves in a virtual σ + ρ system by the Bessel or Hankel spherical functions with orbital angular momentum Λ.…”

“…Therefore, once the model is changed and extra mechanisms are added, the potential parameter values not only can but should vary within reasonable limits. While taking into account an additional term to the amplitude of elastic scattering, associated with only dineutron transfer [36,37], we had to use an opti cal potential of α 6 He interaction too deep and narrow, which did not fully correspond to the physical picture.…”

“…The Green's function in (36) describes free motion of virtual clusters ρ and σ. In the position rep resentation it is found to be of the following form [32]:…”

“…A respective weight factor was accounted for while calculating a reduced decay width of 6 Не → 5 Не + n. We determined the spectroscopic factor of a dineutron (the pole diagram in Fig. 8a) via that of a deuteron in 6 Li (it is equal to 1.68 [36]), while the spectroscopic factors of the lower and upper parts of the quadrangle diagram shown in Fig. 8b ( = 0, 1) are presented in Table 1.…”

Exploring the neutron dripline two neutrons at a time: The first observations of the 26O and 16Be ground state resonances

“…The limiting cases for the simultaneous two-neutron emission would be a phase-space decay where the neutrons exhibit no correlation or the emission of a dineutron cluster. The more exotic dineutron decay is of great interest as multiple studies have shown indirect evidence for the presence of a dineutron in neutron-rich halo nuclei, such as 6 He and 11 Li [15][16][17][18][19][20][21]. However, a direct measurement of a dineutron-like emission has not yet been observed.…”