CLAS physics database search results Measurement E151M230 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Data errors Systematic errors degrees 0.65 282 0.6268 0.4497 0.0491 0.75 282 0.2121 0.5136 0.0327 0.85 102 0.5095 0.5133 0.0435 0.95 102 0.9015 0.4219 0.0634 0.65 294 -0.3693 0.5384 0.0373 0.75 282 -0.9257 0.413 0.0633 0.85 102 2.9653 2.9653 0.1811