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Register a new userDissociation of relativistic nuclei in peripheral interactions in nuclear track emulsion
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Possibilities of the nuclear emulsion technique for the study of the systems of several relativistic fragments produced in the peripheral interactions of relativistic nuclei are discussed. The interactions of the $^{10}$B and $^{9}$Be nuclei in emulsion are taken as an example to show the manifestation of the cluster degrees of freedom in relativistic fragmentation. For the case of the relativistic $^{9}$Be nucleus dissociation it is shown that exact angular measurements play a crucial role in the restoration of the excitation spectrum of the alpha particle fragments. The energy calibration of the angular measurements by the $^{9}$Be nucleus enables one to conclude reliably about the features of internal velocity distributions in more complicated systems of relativistic $alpha$ particles.
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The technique of nuclear track emulsions is used to explore the fragmentation of light relativistic nuclei down to the most peripheral interactions - nuclear white stars. A complete pattern of therelativistic dissociation of a $^8$B nucleus with target fragment accompaniment is presented. Relativistic dissociation $^{9}$Be$to2alpha$ is explored using significant statistics and a relative contribution of $^{8}$Be decays from 0$^+$ and 2$^+$ states is established. Target fragment accompaniments are shown for relativistic fragmentation $^{14}$N$to$3He+H and $^{22}$Ne$to$5He. The leading role of the electromagnetic dissociation on heavy nuclei with respect to break-ups on target protons is demonstrated in all these cases. It is possible to conclude that the peripheral dissociation of relativistic nuclei in nuclear track emulsion is a unique tool to study many-body systems composed of lightest nuclei and nucleons in the energy scale relevant for nuclear astrophysics.
Status and prospects of nuclear clustering studies by dissociation of relativistic nuclei in nuclear track emulsion are presented. The unstable $^{8}$Be and $^{9}$B nuclei are identified in dissociation of the isotopes $^{9}$Be, $^{10}$B, $^{10}$C and $^{11}$C, and the Hoyle state in the cases $^{12}$C and $^{16}$O. On this ground searching for the Hoyle state and more complex $alpha$-particle states in the dissociation of the heavier nuclei is suggested. A detailed study of a low-density baryonic matter arising in dissociation of the heaviest nuclei is forthcoming long-term problem. An analysis of nuclear fragmentation induced by relativistic muons is proposed to examine the mechanism dissociation.
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%.
The results of investigations of the dissociation of a $^{14}$N nucleus of momentum 2.86~A~GeV/c in photo-emulsion are presented. The main characteristics of these reactions, that is the cross sections for various fragmentation channels, are given. The fragmentation was analyzed by means of an invariant approach. The momentum and correlation characteristics of $alpha$ particles for the $^{14}$N$to3alpha$+X channel in the laboratory system and the rest systems of 3$alpha$ particles were considered. The results obtained for the $^{14}$N nucleus are compared with similar data for the $^{12}$C and $^{16}$O nuclei.
A role of the unstable nuclei ${}^{6}$Be, ${}^{8}$Be and ${}^{9}$B in the dissociation of relativistic nuclei ${}^{7,9}$Be, ${}^{10}$B and ${}^{10,11}$C is under study on the basis of nuclear track emulsion exposed to secondary beams of the JINR Nuclotron. Contribution of the configuration ${}^{6}$Be + $mit{n}$ to the ${}^{7}$Be nucleus structure is 8 $pm$ 1% which is near the value for the configuration ${}^{6}$Li + $mit{p}$. Distributions over the opening angle of $alpha$-particle pairs indicate to a simultaneous presence of virtual ${}^{8}$Be$_{g.s.}$ and ${}^{8}$Be$_{2^+}$ states in the ground states of the ${}^{9}$Be and ${}^{10}$C nuclei. The core ${}^{9}$B is manifested in the {${}^{10}$C} nucleus with a probability of 30 $pm$ 4%. Selection of the ${}^{10}$C white stars accompanied by ${}^{8}$Be$_{g.s.}$ (${}^{9}$B) leads to appearance in the excitation energy distribution of 2$alpha$2$mit{p}$ quartets of the distinct peak with a maximum at 4.1 $pm$ 0.3 MeV. ${}^{8}$Be$_{g.s.}$ decays are presented in 24 $pm$ 7% of 2He + 2H events of the ${}^{11}$C coherent dissociation and 27 $pm$ 11% of the 3He ones. The channel ${}^{9}$B + H amounts 14 $pm$ 3%. The ${}^{8}$Be$_{g.s.}$ nucleus is manifested in the coherent dissociation ${}^{10}$B $to$ 2He + H with a probability of 25 $pm$ 5% including 14 $pm$ 3% of ${}^{9}$B decays. A probability ratio of the mirror channels ${}^{9}$B + $mit{n}$ and ${}^{9}$Be + $mit{p}$ is estimated to be 6 $pm$ 1.
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