CLAS physics database search results Measurement E151M2103 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.95 234 5.2257 2.5248 0.4812 0.95 270 3.7776 2.5477 0.3485 0.95 282 1.9751 2.6436 0.184 0.75 114 -0.7804 0.8188 0.059 0.95 222 3.5905 1.4173 0.2355