CLAS physics database search results Measurement E151M3139 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 222 -0.2397 0.2428 0.0304 0.75 198 -0.1723 0.2345 0.0302 0.75 210 -0.3568 0.2449 0.0308 0.75 270 -0.4092 0.2206 0.0311 0.85 138 -0.0259 0.2767 0.03