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.
Churchwell, W. Xu et al including S., et al. “PWIA Extraction of the Neutron Magnetic Form Factor from Quasi-Elastic 3He(e,e') at Q2=0.3 to 0.6 (GeV/c)2,.” Phys. Rev. C, vol. 67, 2003.
Xu, W., et al. “Plane-wave impulse approximation extraction of the neutron magnetic form factor from quasielastic 3He→(e→,e′) at Q2 = 0.3 to 0.6 (GeV/c)2.” Physical Review C Nuclear Physics, vol. 67, no. 1, 2003, pp. 122011–15.
Nagadi, M. M., et al. “Dispersive optical-model and coupled-channels descriptions of neutron scattering from 27Al and 59Co up to 80 MeV.” Physical Review C Nuclear Physics, vol. 68, no. 4, 2003, pp. 446101–08.
Gueorguiev, G. P., et al. “Modeling fast neutron shielding for the direct nn-scattering experiment.” International Meeting on Nuclear Applications of Accelerator Technology: Accelerator Application in a Nuclear Renaissance, Jan. 2003, pp. 53–58.
Madey, R., et al. “Measurements of GEn/GMn from the 2H(e→, e′n→)1H Reaction to Q2 = 1.45 (GeV/c)2.” Physical Review Letters, vol. 91, no. 12, 2003, pp. 1220021–25.
Witała, H., et al. “Effects of the magnetic moment interaction between nucleons on observables in the 3N continuum.” Physical Review C Nuclear Physics, vol. 67, no. 6, 2003, pp. 640021–28.
Furman, W. I., et al. “Direct measurement of the neutron-neutron scattering cross section at the reactor YAGUAR.” Journal of Physics G: Nuclear and Particle Physics, vol. 28, no. 10, Oct. 2002, pp. 2627–41. Scopus, doi:10.1088/0954-3899/28/10/308. Full Text
Xiong, F., et al. “Precision measurement of the spin-dependent asymmetry in the threshold region of 3H→e(e→, e′).” Physical Review Letters, vol. 87, no. 24, Dec. 2001, pp. 2425011–15.
Xiong, F., et al. “Precision measurement of the spin-dependent asymmetry in the threshold region of 3He(e, e').” Physical Review Letters, vol. 87, no. 24, Dec. 2001, p. 242501. Epmc, doi:10.1103/physrevlett.87.242501. Full Text