CLAS physics database search results Measurement E151M3167 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.75 78 0.0463 0.2637 0.03 0.75 210 -0.0323 0.2496 0.03 0.75 258 -0.0041 0.2846 0.03 0.75 270 -0.2394 0.2603 0.0304 0.75 282 0.1613 0.2558 0.0302