CLAS physics database search results Measurement E151M39 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.45 282 -0.2365 0.5727 0.0403 0.55 270 -0.7485 0.3919 0.0903 0.55 282 -0.2831 0.5389 0.044 0.65 294 -0.3986 0.5096 0.0544 0.75 270 -0.2984 0.4753 0.0453 0.85 126 -0.2191 0.56 0.039 0.85 150 -0.0001 0.564 0.03 0.95 186 -0.0416 0.4606 0.0304