부산대학교 도서관

The azirnuthal distribution of planes containing e^i/e pairs from high-energy photon materialization is reminiscent, through a quadrupole anisotropy, of the degree and position angle of linear polarization of the incident photons. Data on open pairs in the COS-B spark chamber are used in a search for such an effect in > 50 MeV photons from bright sources, such as Vela, Crab, Geminga and a reference galactic plane region in Cygnus. After a description of the method and the related simulations and tests, the analysis of the available data shows no anisotropy for the other sources, but for the Vela pulsar a low-chance-probability effect is found apparently implying a high (~ 100%) degree of linear polarization for the Vela photons. This is discussed in light of the physics of the production mechanisms as well as of their geometry.