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

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 Hoyle's state to the \({}^{12}\)C \(\to\) 3\(\alpha\) dissociation is 10-15\%.