Compton scattering from He 4 at the TUNL HIγ S facility

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© 2020 American Physical Society. Differential cross sections for elastic Compton scattering from He4 have been measured with high statistical precision at the High Intensity γ-ray Source at laboratory scattering angles of 55°, 90°, and 125° using a quasi-monoenergetic photon beam with a weighted mean energy value of 81.3 MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from He4 to fully interpret the data.





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Li, X, MW Ahmed, A Banu, C Bartram, B Crowe, EJ Downie, M Emamian, G Feldman, et al. (2020). Compton scattering from He 4 at the TUNL HIγ S facility. Physical Review C, 101(3). 10.1103/PhysRevC.101.034618 Retrieved from

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Calvin R. Howell

Professor of Physics

Professor Howell’s research is in the area of experimental nuclear physics with emphasis on the quantum chromodynamics (QCD) description of low-energy nuclear phenomena, including structure properties of nucleons and nuclei and reaction dynamics in few-nucleon systems.   The macroscopic properties of nucleon structure and the residual strong nuclear force between neutrons and protons in nuclei emerge from QCD at distances where the color interactions between quarks and gluons are strong.  However, the details of the mechanisms that generate the strong nuclear force are not well understood.   Effective field theories (EFT) and Lattice QCD calculations provide theoretical frames that connect low-energy nuclear phenomena to QCD.  Professor Howell and collaborators are conducting experiments on few-nucleon systems that test predictions of ab-initio theory calculations for the purpose of providing insight about the QCD descriptions of low-energy nucleon interactions and structure.  His current projects include measurements of the electromagnetic and spin-dependent structure properties of nucleons via Compton scattering on the proton and few-nucleon systems and studies of two- and three-nucleon interactions using few-nucleon reactions induced by photons and neutrons.  In the coming years, a focus will be on investigating the neutron-neutron interaction in reactions and inside nuclei.  In addition, his work includes applications of nuclear physics to national nuclear security, medical isotope production, and plant biology. Most of his research is carried out at the High Intensity Gamma-ray Source and the tandem laboratory at TUNL. 

Diane M Markoff

Adjunct Professor in the Department of Physics

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