Systematization of the yields of products of photonuclear reactions on enriched-tin targets at the bremsstrahlung-photon
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EMENTARY PARTICLES AND FIELDS Experiment
Systematization of the Yields of Products of Photonuclear Reactions on Enriched-Tin Targets at the Bremsstrahlung-Photon Endpoint Energy of 4.5 GeV A. R. Balabekyan* Yerevan State University, 1 Alex Manoogian Str., Yerevan 375049, Republic of Armenia Received April 8, 2008
Abstract—Yields of photonuclear-reaction products formed in targets from separated tin isotopes under the effect of beams of bremsstrahlung photons whose endpoint energy is 4.5 GeV were investigated. The systematization performed on this basis revealed an isoscaling character of the behavior of the production yields for various regions of reaction-product masses. PACS numbers: 25.20.-x DOI: 10.1134/S1063778808110112
Investigation of cross sections for nuclear reactions is of importance both for obtaining deeper insight into reaction mechanisms and for refining our ideas of the structure of nuclei. For a long time, the attention of physicists has been focused on finding a unified analytic form that would describe cross sections for deep-inelastic splitting reactions on nuclei of various isotopes. The most successful approximation was obtained by Rudstam in the form of a fiveparameter expression [1]. Via systematizing a vast body of experimental data, he was able to obtain, to a satisfactory precision (within a factor of 2 to 3), estimates of cross sections for splitting reactions over a broad region of target mass numbers and projectile energies. But experimental data concerning the splitting of targets that have a natural isotopic composition could not provide information of sufficient precision about the isospin effect on the probability of formation of various products [2–7]. However, the effect of the isotopic composition of target and residual nuclei on the formation of reaction products was indicated in a number of studies [8–10]. Experiments with targets from separated tin isotopes were performed at the Yerevan electron accelerator in a beam of bremsstrahlung photons whose endpoint energy is Eγ max = 4.5 GeV [11–13]. A systematization of experimental data suggested an exponential dependence of photonuclear-reaction yields on the third projection of the isospin of primary nuclei and reaction products. In view of this, the modified Rudstam formula [14] was supplemented with *
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additional terms that take into account this dependence [15, 16]. Targets from separated tin isotopes were also irradiated at the phasotron and synchrotron of the Joint Institute for Nuclear Research with 0.66-, 1.0-, and 8.1-GeV proton beams. These investigations revealed that an isotopic dependence is present in the case of proton-induced nuclear reactions as well [17, 18]. Cross sections for reactions induced by highenergy ion–ion interactions have been vigorously studied in recent years. The authors of some studies [19–26] explored the ratios of cross sections for the production of light fragments in targets of different isotopic composition. The systematization constructed in [23] for experimental data on is
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