Generation and detection of the polarization of multi-GeV photons by use of two diamond crystals

Presented are experimental results for the difference in pair production pr obability (the asymmetry) for 5-150 GeV photons polarized parallel and perp endicular to a (110) plane in a 1.5 mm thick diamond [100] crystal. The pho tons are produced by interaction of 150 GeV electrons with an aligned diamo nd [100] crystal of 0.5 mm thickness. A significant asymmetry is found over the whole energy range, which corresponds to a high degree of linear polar ization of the photons as well as a difference in the refractive index, Thi s proof-of-principle result gives the possibility of producing high energy photons with circular polarization by use of a crystal. This might open for several opportunities in high energy physics like for instance the investi gation of the contribution of the gluons to the spin of the nucleon. (C) 19 99 Published by Elsevier Science B.V. All rights reserved.