CLAS physics database search results Measurement E151M1603 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 126 -1.3604 0.8075 0.0869 0.75 258 -0.5561 0.8708 0.0448 0.95 270 -0.1218 0.7376 0.0309 0.65 234 1.9439 0.8702 0.1169 0.75 258 1.1033 0.81 0.0708 0.85 246 1.1376 1.0504 0.0726 0.85 258 0.9111 0.9892 0.0609 0.95 258 0.7551 0.8652 0.0532