CLAS physics database search results Measurement E151M1813 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.65 90 -0.5436 0.8315 0.0446 0.65 102 0.3792 0.8274 0.0378 0.75 90 0.7254 0.8439 0.0532 0.75 102 0.0275 0.8565 0.03 0.75 246 0.837 0.8404 0.0589 0.75 258 -0.2606 0.7461 0.0339 0.75 270 -1.0664 0.7316 0.0712 0.85 246 -0.096 0.7507 0.0306 0.85 270 -0.0355 0.855 0.0301 0.85 282 0.0454 0.7141 0.0301 0.85 294 -1.8441 0.5608 0.1157 0.95 282 0.9642 0.6723 0.0657 0.95 294 0.61 0.7222 0.0476