CLAS physics database search results Measurement E151M2429 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 114 0.223 0.998 0.0341 0.85 126 -2.1898 0.8337 0.1616 0.85 186 -0.5399 1.073 0.0493 0.85 198 -0.2146 1.1317 0.0338 0.85 210 -2.0633 0.8955 0.1526