CLAS physics database search results Measurement E151M3422 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 258 -0.2606 0.2467 0.0304 0.75 282 -0.0984 0.2715 0.0301 0.85 282 0.007 0.2803 0.03 0.85 318 -0.0662 0.2738 0.03 0.85 330 -0.2561 0.2423 0.0304