CLAS physics database search results Measurement E151M1011 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 78 0.5782 0.7336 0.0518 0.75 90 1.0769 0.8904 0.0842 0.75 258 0.4575 0.7746 0.0449 0.75 306 0.2147 0.7394 0.0339 0.85 270 -0.5474 0.6678 0.05 0.85 282 0.1713 0.7453 0.0325