CLAS physics database search results Measurement E151M2418 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 282 -0.1289 0.9705 0.0314 0.75 114 -1.8385 1.0357 0.1366 0.75 186 -0.7634 1.0838 0.063 0.75 270 -0.6261 0.9844 0.0544 0.85 102 -1.6007 0.898 0.1199 0.85 114 0.2758 0.8816 0.0361 0.85 126 0.9627 0.8423 0.076 0.85 138 -1.3634 1.0598 0.1033 0.85 186 0.1103 0.8067 0.031 0.85 198 -1.1072 0.7923 0.0857 0.85 210 0.2107 0.8098 0.0337 0.85 222 -0.5292 0.9198 0.0487