CLAS physics database search results Measurement E151M1261 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.45 282 0.1679 0.6717 0.0355 0.55 270 -0.6135 0.4953 0.0754 0.55 282 0.0492 0.6403 0.0305 0.65 294 -0.3792 0.615 0.0522 0.75 270 -0.3201 0.5579 0.0469 0.85 126 -0.2393 0.658 0.0404 0.85 150 0.3113 0.6375 0.0462 0.95 186 0.8693 0.4757 0.1025