CLAS physics database search results Measurement E151M1023 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.35 78 -0.5252 0.8041 0.0487 0.75 102 0.5641 0.8066 0.051 0.75 246 1.9562 0.9923 0.1461 0.75 258 -0.5232 0.777 0.0486 0.85 126 0.0093 0.8672 0.03 0.85 246 -0.023 0.852 0.03