CLAS physics database search results Measurement E151M3648 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 114 -0.0028 0.2586 0.03 0.75 210 -0.1326 0.2656 0.0301 0.75 282 -0.1391 0.2332 0.0301 0.85 126 0.2117 0.2644 0.0303 0.85 186 -0.2911 0.235 0.0306 0.85 198 0.0387 0.2302 0.03 0.85 270 -0.4922 0.2156 0.0316