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Etude des décroissances multi-neutron des isotopes lourds d'hélium et d'hydrogène

Abstract : The search for multineutron systems, nuclei composed of only neutrons, has been going on since the early 1960s. While the absence of dineutrons and trineutrons seems clear in experiments, the tetraneutron continues to fuel a lively debate. To this day, experiments have been ambiguous and contradictory. We propose to search for these systems in very neutron-rich nuclei: helium-7 whose excited state seems to decay in α + 3n and hydrogen-7 whose existence is at the heart of questions. For the first time, we present an experiment with very high statistics in which we have directly measured the momentum of up to four coincident neutrons. A beam of 8He at 156 MeV/nucleon was sent to the cryogenic target MINOS to form 7He and 7H by knockout reaction 8He(p,pn)7He*{α + 3n} and 8He(p, 2p)7H{t + 4n} at the RIBF of RIKEN (Japan). The complete kinematics of the reactions were measured. We will present the very first results of this experiment. The analysis of the data allowed us to put in evidence for the first time the direct character of the decay of the excited state 7He*(5/2−) by emission of three neutrons. The results of a thorough analysis of the correlations between the decay particles show the absence of trineutron. The first results obtained on the 8He(p, 2p) channel are at odds with the conclusions of former experimental works.
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Submitted on : Monday, March 21, 2022 - 1:43:09 PM
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  • HAL Id : tel-03615243, version 1

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Cyril Lenain. Etude des décroissances multi-neutron des isotopes lourds d'hélium et d'hydrogène. Physique [physics]. Normandie Université, 2021. Français. ⟨NNT : 2021NORMC260⟩. ⟨tel-03615243⟩

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