Polarized photon measurements of the 12C(gamma over-right- arrow,pp) and 12C(gamma over-right-arrow,pn) reactions for Egamma=160-350 MeV

Powrie, C.J.Y. et al. (2001) Polarized photon measurements of the 12C(gamma over-right- arrow,pp) and 12C(gamma over-right-arrow,pn) reactions for Egamma=160-350 MeV. Physical Review C, 6403(3), art 034602. (doi: 10.1103/PhysRevC.64.034602)

Abstract

The C-12([([gamma])over right arrow], pp) and C- 12([([gamma])over right arrow], pn) reactions have been studied for E-gamma = 160-350 MeV using linearly polarized photons from the Glasgow tagged photon spectrometer at the Mainz microtron MAMI. Both reaction channels show a negative photon asymmetry Sigma for missing energies E-m below 70 MeV, where direct emission nucleon pairs is expected, A strong peak at low E-m is observed in Sigma ((gamma ,pp)), but not in Sigma ((gamma ,pn)). Further differences between the two reaction channels are observed in the E-gamma dependence of Sigma and in the angular distributions of differential cross sections for photons polarized parallel, or perpendicular, to the reaction plane. Theoretical calculations using an unfactorized distorted wave treatment of direct two-nucleon emission do not agree with the magnitude of the photon asymmetry or the angular dependence of the differential cross sections for either channel. For E- m gt 70 MeV and E gamma gt 250 MeV, Sigma has a substantial negative value which is similar for both reaction channels. This is attributed to two-step reactions following initial quasifree pion production.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: McGeorge, Dr John and Branford, Prof Derek and Owens, Professor Robert and Ireland, Professor David and Livingston, Dr Kenneth and MacGregor, Professor Douglas and Annand, Dr John and Kellie, Dr James and Watts, Dr Daniel and Glazier, Dr Derek
• Authors: Powrie, C.J.Y., McGeorge, J.C., MacGregor, I.J.D., Ahrens, J., Annand, J.R.M., Arneil, J.F., Beck, R., Branford, D., Franczuk, S., Glazier, D.I., Grabmayr, P., Hall, S., Hehl, T., Harty, P.D., Ireland, D.G., Kellie, J.D., Livingston, K., Natter, F.A., Oberkirsch, S., Owens, R.O., Ryckebusch, J., Sauer, M., Settele, A., and Watts, D.P.
• Subjects: Q Science > QC Physics
• College/School: College of Science and Engineering > School of Physics and Astronomy
• Journal Name: Physical Review C
• ISSN: 0556-2813