Tseng's calculations of low energy pair production |
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| Institution: | 1. Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada, Spain;2. Centro Estatal de Atención Oncológica, SSM, Gertrudis Bocanegra 300, Col. Cuauhtémoc, C.P. 58020 Morelia, Michoacán, México;1. Institute of Modern Physics, Fudan University, Shanghai 200433, China;2. Key Laboratory of Nuclear Physics and Ion-beam Application (MOE), Fudan University, Shanghai 200433, China;3. Department of Nuclear Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran;4. Radiation Oncology Department, Cancer Institute, Tehran University of Medical Sciences, Tehran, Iran;5. School of Medicine, Jiroft University of Medical Sciences, Jiroft, Iran;1. Department of Physics, Sri Venkateswara University, Tirupati 517502, India;2. Department of BIN Fusion Technology & Department of Polymer-Nano Science and Technology, Chonbuk National University, Jeonju, Jeonbuk, Republic of Korea;3. Department of Chemistry and Chemical Institute for Functional Materials, Pusan National University, Busan 609-735, Republic of Korea;1. Department of Electronic Engineering, Yeungnam University, Gyeongsan 38541, South Korea;2. Department of Physics, Siddartha Educational Academy Group of Institutions, Tirupati 517502, India;3. Department of Physics, Raghu Engineering College, Visakhapatnam-531162, India;1. School of Mathematics and Computer Applications, Thapar University, Patiala-04, Punjab, India;2. Department of Computer Science and Engineering, Tezpur University, Tezpur-28, Assam, India |
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| Abstract: | We review the theoretical work 1971–1997 of H.K. Tseng on low energy pair production. In this work numerical calculations were performed in independent particle approximation in a screened self-consistent central potential, expanding the S-matrix element in partial waves and multipoles. Sampling techniques in partial waves and multipoles were used to extend the calculations to higher energies (up to 10 Mev). Total cross sections, the positron energy spectrum, the positron angular distributions, and the positron–photon polarization correlations were studied. Agreement was obtained with most experiments, although some anomalies remained at the lowest energies (particularly at 1082 keV). Atomic screening of the nuclear charge decreases cross sections at higher energies, as described by a form factor in the momentum transfer to the nucleus. In an intermediate energy regime point Coulomb results in a shifted energy spectrum may be used. At low energies screening increases cross sections, and this is characterized in terms of a normalization screening factor which describes the change in magnitude of electron and positron wave functions at small distances. In this low energy regime angular distribution shapes and polarization correlations are independent of screening. |
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