Investigation of the ReactionHe4(He

Abstract

The reaction 4 He( 4 He, 4 He) 4 He* was investigated, using a 64-MeV a-particle beam. Absolute differential cross sections for the state near 20-MeV excitation are reported for the angular range 12.5°<0 o . m .<74°. We measure the excitation energy of this state to be 20.28=b0.05 MeV and the width to be 0.41 ±0.05 MeV. The shape and position of this state are shown to be consistent with an analysis based on the known properties of low-energy p-*H scattering.

The MAGNEX spectrometer: Results and perspectives

“…In this way the analysis of the shape of the experimental angular distribution can also signal the presence of non-monopole contributions in the 20.4 MeV resonance region. The extraction of the position and width of the 0 + resonance with better accuracy with respect to the previous ( 4 He, 4 He) measurements [161], [162] is also planned, to hopefully shed light on the disagreement with the extractions from (e,e') data [163]. Precise data will be useful to the ab-initio theory community, in view of a better understanding and constraining of the nuclear Hamiltonians.…”

Properties of the (α,α*) Reaction at Very Forward Angles: Coupled-Channels Effects in Single and Mutual Excitation

“…The data from the present investigation are displayed as open circles. In order to make the monopole strength observed in our (a 9 a*) measurements compatible with the strength obtained from direct measurements such as the 4 He(a, a') 4 He* measurement of Gross et al, 8 our (a, a*) cross sections should be corrected for the limited relative energy range be- cause of the detector arrangement and the unobserved n + 3 He channel. With use of the Breit-Wigner parameter set 9 a =3.3 fm, E 0 =0.6 MeV, y p 2 =3.53 MeV, and y* = 1.74 MeV to describe the a?…”

“…13 The total wave function of the incoming a-a channel was symmetrized. 10 An a-a optical potential obtained 14 at£ a = 47.1 MeV, was used; however, here the imaginary depth had to be changed drastically (see Table I) to obtain a reasonable fit to the elastic and inelastic scattering data of Gross etal,, 8 (not shown) obtained at E a ~ 64 MeV. The uncertainties in j3 0 obtained from this analysis are estimated around 50% because of optical-model potential ambiguities.…”

Study of the 4He(4He,4He)4He* inelastic scattering at the MAGNEX facility

“…In the present work, the inelastic scattering reaction 4 He + 4 He → 4 He + 4 He * → 4 He + 3 H + 1 H was simulated for both the resonant (0 + ) and the non -resonant breakup, while the 4 He + 4 He → 4 He + 4 He * → 4 He + 3 He + n was simulated only for the non -resonant breakup since its threshold is higher than the 0 + resonant region. The transfer processes 4 He + 4 He → 3 H + 5 Li → 4 He + 3 H + 1 H and 4 He + 4 He → 3 He + 5 He → 4 He + 3 He + n leading to the same final channels were also simulated. The experimental data compared with the kinematical simulations are illustrated in Figs.…”

“…No bound states are existing in its level scheme however it exhibits, very close to the breakup threshold, a pronounced resonance with the same spin and parity (0 + ) as the ground state. Several investigations have been performed so far aiming at shedding light on the characteristics of this resonance either by using a 4 He(e,e΄) 4 He * [1][2][3][4] or a He( 4 He, 4 He) 4 He * [5][6] reaction.…”