CLAS physics database search results Measurement E151M1190 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.85 102 1.3406 0.9525 0.1025 0.85 210 0.6966 0.9559 0.0591 0.85 222 0.5414 0.8222 0.0497 0.95 198 -0.0223 0.9067 0.03