232 articles – 3596 references  [version française]
 HAL: in2p3-00674911, version 1
 arXiv: 1107.1684
 Physical Review Letters 108 (2012) 052504
 First direct mass-measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He
 (2012)
 The first direct mass-measurement of $^{6}$He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of $^{8}$He was determined with improved precision over our previous measurement. The obtained masses are $m$($^{6}$He) = 6.018 885 883(57) u and $m$($^{8}$He) = 8.033 934 44(11) u. The $^{6}$He value shows a deviation from the literature of 4$\sigma$. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) fm and 1.959(16) fm for $^{6}$He and $^{8}$He respectively. We present a detailed comparison to nuclear theory for $^6$He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.
 Research team: CSNSM SNO
 Subject(s) : Physics/Nuclear Experiment