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)

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Publisher's URL: http://dx.doi.org/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:Branford, Prof Derek and Livingston, Dr Kenneth and Watts, Dr Daniel and Glazier, Dr Derek and McGeorge, Dr John and Owens, Professor Robert and Ireland, Professor David and MacGregor, Professor I and Annand, Dr John and Kellie, Dr James
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

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