CLAS physics database search results Measurement E151M1202 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.85 90 -0.9667 0.7075 0.0768 0.85 186 -0.294 0.8627 0.0369 0.85 210 -0.9105 0.6984 0.073 0.95 222 1.6502 1.002 0.1243