Application of Nuclear Track Emulsion in Search for the Hoyle State in Dissociation of Relativistic 12C Nuclei

In dissociation in nuclear track emulsion of 4.5 and 1 A GeV/ c 12 C nuclei, the formation of triplets of α particles in the Hoyle state (the second excited state 0 + ) is observed. This state is identified by the invariant mass, calculated from pair angles in the α triples in approximation of conservation of momentum per nucleon of the parent nucleus. An estimate of the contribution of the Hoyle state to the dissociation of 12 C→ 3α is 10–15%.