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تسجيل مستخدم جديدClustering features of the $^7$Be nucleus in relativistic fragmentation
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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.
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Recent studies of clustering in light nuclei with an initial energy above 1 A GeV in nuclear treack emulsion are overviewed. The results of investigations of the relativistic $^9$Be nuclei fragmentation in emulsion, which entails the production of He
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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 product
ion of unusual states, for which a regrouping of nucleons beyond the $alpha$-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 Hoyl
e state. These extremely short-lived states are identified by invariant masses calculated from the angles in 2$alpha$-pairs, 2$alpha p$- and 3$alpha$-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 formation of $^{8}$Be nuclei and the multiplicity of accompanying $alpha$-particles in the dissociation of relativistic $^{16}$O, $^{22}$Ne, $^{28}$Si, and $^{197}$Au nuclei. On the above basis, estimates of this correlation are presented for the unstable $^{9}$B nucleus and the Hoyle state. The enhancement in the $^{8}$Be contribution to dissociation with the $alpha$-particle multiplicity has been found. Decays of $^{9}$B nuclei and Hoyle states follow the same trend.
The $^3$He($alpha$,$gamma$)$^7$Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass n
umber of the reaction partners makes it also suitable for testing microscopic calculations. Despite the high number of experimental studies, none of them addresses the $^3$He($alpha$,$gamma$)$^7$Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the $^6$Li(p,$gamma$)$^7$Be reaction suggested a new level in $^7$Be, which would also have an impact on the $^3$He($alpha$,$gamma$)$^7$Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the $^3$He($alpha$,$gamma$)$^7$Be reaction cross section in the energy range of the proposed level. For this investigation the activation technique was used. A thin window gas-cell target confining $^3$He gas was irradiated using an $alpha$ beam. The $^7$Be produced was implanted into the exit foil. The $^7$Be activity was determined by counting the $gamma$ rays following its decay by a well-shielded high-purity germanium detector. Reaction cross sections have been determined between $E_{cm} = 4.0 - 4.4$ MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies. A constant cross section of around 10.5 $mu$barn was observed around the $^7$Be proton separation energy. An upper limit of 45 neV for the strength of a $^3$He($alpha$,$gamma$)$^7$Be resonance is derived.
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