CLAS physics database search results Measurement E151M1973 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 258 -1.558 1.7466 0.1463 0.85 246 -0.9358 1.9037 0.0911 0.65 258 -0.881 0.6413 0.0647 0.75 258 -0.12 0.5908 0.031 0.75 270 -0.3769 0.4846 0.0387 0.85 114 1.094 0.6918 0.0772 0.85 126 -0.4109 0.7272 0.0402 0.85 258 0.137 0.6649 0.0313 0.85 270 -1.0027 0.6404 0.0718