CLAS physics database search results Measurement E151M3336 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 78 0.0263 0.2549 0.03 0.85 90 -0.0083 0.2274 0.03 0.85 222 -0.0673 0.2512 0.03 0.85 246 -0.111 0.233 0.0301 0.85 258 -0.0689 0.26 0.03