CLAS physics database search results Measurement E151M1214 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.75 186 -0.7386 0.8463 0.0618 0.85 102 -0.1637 0.8737 0.0323 0.85 114 -0.1757 0.8497 0.0326 0.85 126 0.2322 0.9471 0.0345 0.85 210 -0.9124 0.7662 0.0731