CLAS physics database search results Measurement E151M2077 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 102 -0.4909 0.6716 0.0438 0.75 246 0.9697 0.7315 0.0698 0.85 66 0.3754 0.6738 0.0387 0.85 246 1.451 0.6369 0.099 0.85 270 0.4732 0.7074 0.043 0.65 102 -0.7697 1.8654 0.0768 0.85 270 1.5674 1.6688 0.1471 0.95 294 3.1133 4.7949 0.2877