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Nuclear track emulsion in search for the Hoyle-state in dissociation of relativistic ${}^{12}$C nuclei

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 نشر من قبل Andrey Zaitsev
 تاريخ النشر 2018
  مجال البحث
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Production of ensembles of $alpha$-particle triples associated with the Hoyle state (the second excited state of the ${}^{12}$C nucleus) in peripheral dissociation of relativistic ${}^{12}$C nuclei is studied. Stacks of nuclear track emulsion pellicles exposed to ${}^{12}$C with an energy from hundreds MeV to a few GeV per nucleon serve as the material for studies. The Hoyle state decays are reconstructed via measurement of emission angles of $alpha$ particles with the precision sufficient for identification of the unstable ${}^{8}$Be nucleus. The estimate of the contribution of Hoyles state to the ${}^{12}$C $to$ 3$alpha$ dissociation is 10-15%.



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Production of $alpha$-particle triples in the Hoyle state (HS) in dissociation of ${}^{12}$C nuclei at 3.65 and 0.42 $A$ GeV in nuclear track emulsion is revealed by the invariant mass approach. Contribution of the HS to the dissociation ${}^{12}$C $ to$ 3$alpha$ is (11 $pm$ 3) %. Reanalysis of data on coherent dissociation ${}^{16}$O $to$ 4$alpha$ at 3.65 $A$ GeV is revealed the HS contribution of (22 $pm$ 2) %.
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In the context of the search for triples of relativistic $alpha$-particles in the Hoyle state, the analysis of available data on the dissociation of the nuclei ${}^{12}$C, ${}^{16}$O and ${}^{22}$Ne in the nuclear emulsion was carried out. The Hoyle state is identified by the invariant mass calculated from pair angles of expansion in $alpha$-triples in the approximation of the conservation of the momentum per nucleon of the parent nucleus. The contribution of the Hoyle state to the dissociation of ${}^{12}$C $to$ 3$alpha$ is 11%. In the case of the coherent dissociation of ${}^{16}$O $to$ 4$alpha$ it reaches 22% when the portion of the channel ${}^{16}$O $to$ 2${}^{8}$Be is equal to 5%.
indent First results of the exposure of nuclear track emulsions in a secondary beam enriched by $^9$C nuclei at energy of 1.2 A GeV are described. The presented statistics corresponds to the most peripheral $^9$C interactions. For the first time a di ssociation $^9$C $to3^3$He not accompanied by target fragments and mesons is identified.par
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