CLAS physics database search results Measurement E151M3219 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 246 -0.1073 0.2602 0.0301 0.75 258 -0.0261 0.2351 0.03 0.85 78 -0.318 0.2355 0.0307 0.85 102 0.1303 0.2598 0.0301 0.85 270 0.4071 0.2415 0.0311 0.85 294 -0.0148 0.2258 0.03