CLAS physics database search results Measurement E151M1243 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 258 -0.5719 0.4581 0.0711 0.55 270 -0.1188 0.5161 0.0329 0.65 234 0.6036 0.5792 0.0744 0.65 246 0.0065 0.4503 0.03 0.65 258 0.1685 0.4876 0.0355 0.65 270 -0.8062 0.4667 0.0958 0.75 174 -0.3755 0.6116 0.0519 0.75 246 0.9582 0.4121 0.1122 0.75 258 -0.4202 0.4685 0.0561