CLAS physics database search results Measurement E151M287 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 258 -0.4207 0.5931 0.0397 0.75 138 0.4447 0.6739 0.0407 0.75 246 -0.689 0.5691 0.0522 0.85 102 -0.2751 0.6047 0.0345 0.85 138 0.4278 0.6542 0.04 0.85 294 0.3719 0.6132 0.0378 0.65 282 -0.2101 0.8735 0.0326 0.75 114 -0.5784 0.918 0.046 0.85 114 -0.8967 0.6598 0.0618 0.85 282 0.3114 0.8451 0.0354