CLAS physics database search results Measurement E151M2402 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 222 0.3033 1.0828 0.0372 0.85 90 -0.5975 1.1085 0.0527 0.85 210 0.6367 1.0252 0.0551 0.95 210 2.147 0.8316 0.1586 0.95 222 1.2634 0.9904 0.0964 0.95 234 0.1365 0.9646 0.0316