CLAS physics database search results Measurement E151M988 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_UL Stat. error Syst. error degrees 0.65 270 1.2949 0.8447 0.0993 0.65 306 -0.2497 0.6741 0.0351 0.75 78 0.3587 0.7954 0.0398 0.75 90 0.4066 0.82 0.0422 0.75 258 -0.1578 0.6978 0.0321 0.75 282 1.0447 0.7808 0.082 0.75 294 -0.3088 0.6691 0.0375 0.85 270 -1.1529 0.5041 0.0894 0.85 306 1.0588 0.7472 0.083 0.95 258 -1.2901 0.4357 0.0989 0.95 294 -0.7744 0.483 0.0641 0.95 318 0.6875 0.675 0.0585