CLAS physics database search results Measurement E151M1134 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 210 -0.48 0.7911 0.0462 0.85 102 -0.3531 0.7314 0.0396 0.85 114 -1.0997 0.6011 0.0858 0.85 126 -0.5251 0.7629 0.0487 0.85 186 0.0665 0.8805 0.0304 0.85 222 1.1512 0.8933 0.0893