CLAS physics database search results Measurement E151M2353 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 234 -0.8985 0.8574 0.0717 0.85 66 -0.0934 0.7553 0.0308 0.85 78 -0.2031 0.6997 0.0334 0.85 210 1.1855 0.9066 0.0911 0.85 234 -0.9079 0.7168 0.0723 0.85 246 0.2685 0.6882 0.0358 0.85 258 0.2423 0.7128 0.0348 0.85 270 -0.3366 0.7783 0.0387 0.95 246 0.9413 0.7167 0.0746 0.95 258 -0.6378 0.7334 0.0551 0.95 270 0.6969 0.6453 0.0588 0.95 282 0.9252 0.745 0.0735 0.95 294 -0.2901 0.6356 0.0366 0.95 306 0.301 0.7093 0.0371