CLAS physics database search results Measurement E151M1670 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 222 -0.5702 1.1169 0.0447 0.75 246 0.1365 1.1259 0.031 0.85 234 -1.4118 0.7899 0.0874 0.85 258 -0.6593 1.2182 0.0487 0.55 234 -0.2124 0.9347 0.0326 0.85 126 -1.1398 0.9959 0.0746 0.85 234 1.3817 0.8221 0.0881