CLAS physics database search results Measurement E151M3325 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.95 234 -0.2495 0.2621 0.0304 0.95 270 -0.6007 0.2297 0.0323 0.95 282 -0.3515 0.2342 0.0308 0.75 114 0.0784 0.2319 0.03 0.95 222 -0.0979 0.2555 0.0301