CLAS physics database search results Measurement E151M422 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.55 210 0.4709 0.6789 0.0418 0.65 222 0.7693 0.6899 0.0563 0.75 222 -0.1677 0.6141 0.0317 0.85 210 0.5168 0.6743 0.0439 0.45 42 0.1545 1.0957 0.0314 0.65 222 -0.2814 0.7928 0.0345 0.75 210 -0.7359 0.8304 0.0535 0.75 222 0.8449 1.2273 0.0591 0.85 222 -0.0172 0.9877 0.03