IV international conference on particle physics and astrophysics

Halo – like structure of unbound 7He

26 Oct 2018, 15:35

15m

Moskvorechye 2 hall (Hotel Intourist Kolomenskoye 4*)

Plenary/section talk Nuclear physics Nuclear physics

Description

$^{7}$He, a particle unstable nucleus is lying in the line of neutron – rich Helium isotopes between $^6$He with a neutron halo and $^{8}$He having a neutron skin [1]. Normally it is taken for granted that the notion “halo” could not be applied to unstable nuclei. However, if the time of life T of a particular nucleus is much larger than the characteristic time τ of flight of the escaping neutron, there is no difference between stable and unstable nuclei. As for $^{7}$He the ratio T/τ ≈ 7 we looked for data which could provide some information on the halo – like structure of $^{7}$He. We applied the Modified diffraction model MDM [2-4] to the charge – exchange reactions $^{6}$Li(t,$^{3}$He)$^{6}$He [5] and $^{7}$Li(t,$^3$He)$^{7}$He [6]. According to MDM the difference of the RMS of the states under study is determined by the difference of the corresponding diffraction radii taken from the differential cross-sections under study. We found that the radius of $^{7}$He is R$_{rms}$ = 2.37±0.38 fm. This value is close to those of $^{6}$He and $^{8}$He 2.48±0.03 fm and 2.52±0.03 fm [1]. The result supports suggestion that neutrons outside $^{4}$He occupy the same orbitals and indicates to smooth transition between halo and skin. The phase distributions of the fragments emitted in the reactions with stopped pions on $^{9}$Be and $^{11}$B [7, 8] showed that the main $^{7}$He decay configurations are $^{6}$He$_{gr.st}$ + n and $^{6}$He* + n confirming the complicated halo – like of $^{7}$He.

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8. Yu. B. Gurov et al., Phys. Part. Nucl. 40, 558 (2009).

Presentation Materials

1. Demyanova Helium-7-MEPhi_ report.ppt