# IV international conference on particle physics and astrophysics

22-26 October 2018
Hotel Intourist Kolomenskoye 4*
Europe/Moscow timezone

## Halo – like structure of unbound 7He

26 Oct 2018, 15:35
15m
Moskvorechye 2 hall (Hotel Intourist Kolomenskoye 4*)

### Moskvorechye 2 hall

#### Hotel Intourist Kolomenskoye 4*

Kashyrskoye shosse, 39B, Moscow, Russia, 115409
Plenary/section talk Nuclear physics

### Speaker

Dr. Alla Demyanova (NRC Kurchatov Institute)

### 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.

1. I. Tanihata, H. Savajols, R. Kanungo, Progress in Particle and Nuclear Physics 68, 215 (2013).
2. A.S. Demyanova et al., Int. J. Mod. Phys. E 17, 2118 (2008).
3. A. N. Danilov, T. L. Belyaeva, A. S. Demyanova, S. A. Goncharov, and A. A Ogloblin. Phys. Rev. C 80, 054603 (2009).
4. A.S. Demyanova, A.A. Ogloblin, S.A. Goncharov, A.N. Danilov, T.L. Belyaeva, W. Trzaska, Phys. Atom. Nucl., 80, 831 (2017).
5. R. H. Stokes and P. G. Young, Phys. Rev. 178 2024 (1969).
6. J. D. Sherman et al., Phys. Rev. C 13, 2122 (1976).
7. M. G. Gornov et al., Nucl. Instrum. Meth. Phys. Res. A 446, 461 (2000).
8. Yu. B. Gurov et al., Phys. Part. Nucl. 40, 558 (2009).

### Primary author

Dr. Alla Demyanova (NRC Kurchatov Institute)

### Presentation Materials

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