CLAS physics database search results Measurement E151M2210 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 270 -0.2085 0.8748 0.0336 0.65 306 -0.7719 0.7689 0.0635 0.75 78 0.2061 0.8756 0.0335 0.75 90 1.3071 0.8417 0.0994 0.75 258 0.6381 0.8169 0.0551 0.75 282 -0.7179 0.7671 0.0601 0.75 294 -0.7376 0.7819 0.0613 0.85 270 0.6111 0.7351 0.0535 0.85 306 0.9673 0.7614 0.0763 0.95 258 -0.2456 0.7068 0.0349 0.95 294 0.4193 0.6665 0.0427 0.95 318 -0.8388 0.7004 0.0678