Polarized photon measurements of the C-12((gamma)over-right-arrow,pp) and C-12((gamma)over-right-arrow,pn) reactions for E-gamma=160-350 MeV - art. no. 034602

Citation
Cjy. Powrie et al., Polarized photon measurements of the C-12((gamma)over-right-arrow,pp) and C-12((gamma)over-right-arrow,pn) reactions for E-gamma=160-350 MeV - art. no. 034602, PHYS REV C, 6403(3), 2001, pp. 4602
Citations number
45
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Physics
Journal title
PHYSICAL REVIEW C
ISSN journal
0556-2813 → ACNP
Volume
6403
Issue
3
Year of publication
2001
Database
ISI
SICI code
0556-2813(200109)6403:3<4602:PPMOTC>2.0.ZU;2-3
Abstract
The C-12(<(<gamma>)over right arrow>, pp) and C-12(<(<gamma>)over right arr ow>, pn) reactions have been studied for E-gamma = 160-350 MeV using linear ly polarized photons from the Glasgow tagged photon spectrometer at the Mai nz 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 ,p p)), but not in Sigma ((gamma ,pn)). Further differences between the two re action 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 emiss ion 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>7 0 MeV and E gamma >250 MeV, Sigma has a substantial negative value which is similar for both reaction channels. This is attributed to two-step reactio ns following initial quasifree pion production.