CLAS physics database search results Measurement E151M2245 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.35 78 -0.9051 0.9044 0.0722 0.75 102 0.0645 0.8816 0.0304 0.75 246 0.446 0.9252 0.0441 0.75 258 0.8735 0.994 0.0701 0.85 126 -0.2191 1.0083 0.0339 0.85 246 0.5136 1.0228 0.0478