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 $α$-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$α$2$\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.
Dissociation of 1.2 A GeV $^{10}$C nuclei in nuclear track emulsionis is studied. It is shown that most precise angular measurements provided by this technique play a crucial role in the restoration of the excitation spectrum of the 2$α$+2p system. Strong contribution of the cascade process $^{10}$C$\rightarrow ^9$B$\rightarrow ^8$Be identified.
Experimental data on fragmentation channels in peripheral interactions of $^8$B nuclei in nuclear track emulsions are presented. A detailed analysis made it possible to justify selections of events of the electromagnetic-dissociation process $^8$B $\to^7$Be + \emph{p} and to estimate its cross section. Events of $^{10}$C peripheral dissociation that were observed in the same exposure are described.
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 $α$-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 o…
The transverse-momentum distributions and correlation characteristics of relativistic $α$ particles from the coherent dissociation of a carbon nucleus into three $α$ particles at 4.5 GeV/$c$ are studied in lead-enriched emulsion. Comparative analysis of data obtained in ordinary and lead-enriched emulsion stacks is performed. It is shown that the statistical model of rapid fragmentation does not describe the momentum and correlation characteristics of a $α$ particles in the rest frame of the carbon nucleus. The estimated decay temperature of $^{12}$C is weakly dependent on the target atomic ma…
Production of ensembles of $α$-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 $α$ particles with the precision sufficient for identification of the unstable ${}^{8}$Be nucleus. The estimate of the contribution of Hoyle's state to the $…
The charge topology in the fragmentation of $^{10}$C nuclei in a track nuclear emulsion at an energy of 1.2 GeV per nucleon is studied. In the coherent dissociation of $^{10}$C nuclei, about 82% of events are associated with the channel $^{10}$C $\rightarrow$ 2$α+$ 2\emph{p}. The angular distributions and correlations of product fragments are presented for this channel. It is found that among $^{10}$C $\rightarrow$ 2$α+$ 2\emph{p} events, about 30% are associated with the process in which dissociation through the ground state of the unstable $^9$Be$_{g.s.}$ nucleus is followed by $^8$Be$_{g.s.…
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$\to2α$ 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 …
These lecture notes present the capabilities of relativistic nuclear physics for the development of the physics of nuclear clusters. Nuclear track emulsion continues to be an effective technique for pilot studies that allows one, in particular, to study the cluster dissociation of a wide variety of light relativistic nuclei within a common approach. Despite the fact that the capabilities of the relativistic fragmentation for the study of nuclear clustering were recognized quite a long time ago, electronic experiments have not been able to come closer to an integrated analysis of ensembles of r…
The differential cross section in the transverse momentum $Q$ and a total cross section of $(31\pm4)$ mb for the coherent dissociation of a 3-A-GeV/$c$ $^7$Li nucleus through the $^3$H$+^4$He channel have been measured on emulsion nuclei. The observed $Q$ dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction ($Q\le400$ MeV/$c$) and Coulomb $(Q\le50$ MeV/$c$) dissociations are calculated to be 40.7 and 4 mb, respectively…
Slowly extracted relativistic beams of light nuclei and a beam transportation line net system constitute a good base for secondary nuclear beams forming at the LHE accelerator facility. A recent years activity in the field at the Laboratory is connected with a project on study light nuclei structure by means the emulsion technique [1,2]. The paper shortly summarizes results of the work.
Nuclear track emulsion is exposed to a beam of radioactive $^8$He nuclei with an energy of 60 MeV and enrichment of about 80% at the ACCULINNA separator. Measurements of 278 decays of the $^8$He nuclei stopped in the emulsion allow the potential of the $α$ spectrometry to be estimated and the thermal drift of $^8$He atoms in matter to be observed for the first time.
Nuclear track emulsion is exposed to 1.2 A $^9$C GeV nuclei. Pairs of 2$^3$He nuclei having unusually narrow opening angles are observed in channel $^9$C $\rightarrow$ 3$^3$He pointing to the possible 2$^3$He resonance near the production threshold.
Results on the coherent dissociation of relativistic $^9$C nuclei in a nuclear track emulsion are described. These results include the charge topology and kinematical features of final states. Events of C-9 to 3He-3 coherent dissociation are identified.
The charge topology of coherent-dissociation events is presented for $^{11}$C and $^{12}$N nuclei of energy 1.2~\textit{A}~GeV per nucleon bombarding nuclear track emulsions. This topology is compared with respective data for $^{7}$Be, $^{8,10}$B, $^{9,10}$C and $^{14}$N nuclei.
The performance of high-precision mass spectrometry of radioactive isotopes can often be hindered by large amounts of contamination, including molecular species, stemming from the production of the radioactive beam. In this paper, we report on the development of Collision-Induced Dissociation (CID) as a means of background reduction for experiments at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). This study was conducted to characterize the quality and purity of radioactive ion beams and the reduction of molecular contaminants to allow for mass measurements of radioactive isotopes …
The dissociation of relativistic $^{12}$N nuclei having a momentum of 2 GeV/c per nucleon and undergoing the most peripheral interactions in a track emulsion is studied. The picture of charged topology of product ensembles of relativistic fragments and special features of their angular distributions are presented.
The measurement of positron--nucleus collisions was used to estimate the possibility of suppressing background events that simulate $ββ$ decay in the emulsion region adjacent to molybdenum conglomerates. The range of the escape of two relativistic particles from the interaction was found to be $<d> = (0.60\pm 0.03) ~μ$m, which approximately corresponds to the grain size of developed nuclear emulsion. No correlation of the values of d with the angle between two relativistic particles was observed. It was shown that it was possible to exclude $ββ$ decay background from electrons emerging in the …
A nuclear track emulsion was exposed to a mixed beam of relativistic $^{12}$N, $^{10}$C, and $^7$Be nuclei having a momentum of 2 GeV/$c$ per nucleon. The beam was formed upon charge exchange processes involving $^{12}$C primary nuclei and their fragmentation. An analysis indicates that $^{10}$C nuclei are dominant in the beam and that $^{12}$N nuclei are present in it. The charge topology of relativistic fragments in the coherent dissociation of these nuclei is presented.
The fragment separator ACCULINNA in the G. N. Flerov Laboratory of Nuclear Reactions of JINR was used to expose a nuclear track emulsion to a beam of radioactive $^{8}$He nuclei of energy of 60 MeV and enrichment of about 80%. Measurements of decays of $^{8}$He nuclei stopped in the emulsion allow one to evaluate possibilities of $α$-spectrometry and to observe a thermal drift of $^{8}$He atoms in matter. Knowledge of the energy and emission angles of $α$-particles allows one to derive the energy distribution of $α$-decays Q$_{2α}$. The presence of a "tail" of large values Q$_{2α}$ is establis…
The dissociation features in nuclear track emulsion of $^9$Be, $^{9,10}$C, and $^{12}$N nuclei of 1.2 A GeV energy are presented. The data presented for the nucleus $^9$Be can be considered as evidence that there is a core in its structure in the form of 0$^+$ and 2$^+$ states of the $^8$Be nucleus having roughly equal weights. Events of coherent dissociation $^9$C$\rightarrow 3^3$He associated with the rearrangement of the nucleons outside the $α$-clustering are identified. A pattern of the charge fragment topology in the dissociation of $^{10}$C and $^{12}$N nuclei is obtained for the first …
First results of an analysis to determine contribution of decays of the unstable $^{8}$Be and $^{9}$B nuclei and the Hoyle 3$α$-state to dissociation of $^{14}$N $\to$ 3He (+H) are presented. As the research material, layers of nuclear track emulsion longitudinally exposed to 2.9 $A$ GeV/$c$ $^{14}$N nuclei with at the JINR Nuclotron. Under the assumption that the He and H fragments retain momentum per nucleon of the primary nucleus, these unstable states are identified by the invariant mass calculated from the emission angles of the fragments.
In the context of the search for triples of relativistic $α$-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 $α$-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$α$ is 11\%. In the case of the coherent dissociation of ${}^{16}$O $\to$ 4$α$ it reach…
In this work we present some results of the interaction of high energy muons with emulsion nuclei. The interaction results in emission of a number of fragments as a consequence of electromagnetic dissociation of the excited target nuclei. This excitation is attributed to absorption of photons by the target nuclei due to the intense electric field of the very fast incident muon particles. The interactions take place at impact parameters that allows ultra-peripheral collisions to take place, leading to giant resonances and hence multi-fragmentation of emulsion targets. Charge identification, ran…
The invariant mass method is used to identify the $^8$Be and $^9$B nuclei and Hoyle state formed in dissociation of relativistic nuclei in a nuclear track emulsion. It is shown that to identify these extremely short-lived states in the case of the isotopes $^9$Be, $^{10}$B, $^{10}$C, $^{11}$C, $^{12}$C, and $^{16}$O, it is sufficient to determine the invariant mass as a function of the angles in pairs and triples of He and H fragments in the approximation of the conservation of momentum per nucleon of the parent nucleus. According to the criteria established in this way, the contribution of th…
Clustering in light nuclei in fragmentation above 1 A GeV
用相对论不变量方法分析了3.3 A GeV $^{22}$ Ne在核径迹乳胶中的碎裂.用2.1 A GeV的$^{14}$ N和1.2 A GeV的$^{9}$ Be核对乳胶进行辐照，获得了少体解离的新结果。可以断言，使用不变的方法是一种有效的手段，获得的行为的系统，涉及几个He核在一个相对能量接近1兆电子伏每核子的结论。首次观测到1.2 A GeV的$^{8}$ B和$^{9}$ C核在乳胶中碎裂。所提出的结果允许一个证明核天体物理学的少体方面的发展。
Charge topology of fragmentation of 1.2 A GeV $^7$Be nuclei in nuclear track emulsion is presented.The dissociation channels $^4$He + $^3$He, 2$^3$He+ n, $^4$He + 2$^1$H are considered in detail. It is established that the events $^6$Be + n amount about to 27 % in the channel $^4$He + 2$^1$H.
Progress in the study of the peripheral nuclear interactions in $^{14}N$ dissociation at $2.1A GeV$ in nuclear emulsion is outlined. The leading role of the multiple fragmentations in the most peripheral nucleus interactions is discussed. The production of unusual states, for which a regrouping of nucleons beyond the $α$-particle clustering is needed, is identified for this channel.
In the events of peripheral dissociation of relativistic nuclei in the nuclear track emulsion, it is possible to study the emerging ensembles of He and H nuclei, including those from decays of unstable $^{8}$Be and $^{9}$B nuclei, as well as the Hoyle state. These extremely short-lived states are identified by invariant masses calculated from the angles in 2$α$-pairs, 2$αp$- and 3$α$-triplets in the approximation of conservation of momentum per nucleon of the primary nucleus. In the same approach, it is possible to search for more complex states. This paper explores the correlation between the…
In this paper, the correlation between the formation of the unstable $^{8}$Be nucleus and accompanying $α$ particles in the fragmentation of relativistic $^{16}$O, $^{22}$Ne, $^{28}$Si, and $^{197}$Au nuclei in a nuclear track emulsion is investigated. The $^{8}$Be decays are identified in a wide energy range by invariant masses calculated from 2$α$-pair opening angles. The adopted approximations are verified by data on fragmentation of $^{16}$O nuclei in a hydrogen bubble chamber in a magnetic field. An increase in the $^{8}$Be contribution to the dissociation with the growth of $α$-particle …
In a track nuclear photoemulsion exposed to a beamof $^7$Li nuclei accelerated to a momentum of 3 GeV/$c$ per nucleon at the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna), 13 events in which $^7$Li nuclei interacting with protons break up into $^3$H and $^4$He fragments were detected among 3730 inelastic-interaction events. For this fragmentation channel, the cross section was found to be $8\pm2$ mb. The average value of the fragment total transverse momentum was $214\pm5$ MeV/$c$. This value exceedsmarkedly the average value of the transverse-momentumtransfer in t…
