CLAS physics database search results Measurement E151M3244 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 102 0.1906 0.2549 0.0302 0.85 258 0.0253 0.2379 0.03 0.85 282 0.7209 0.1842 0.0333 0.85 294 0.117 0.24 0.0301 0.95 294 0.3595 0.2429 0.0308