CLAS physics database search results Measurement E151M2391 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.85 78 -0.6596 0.8765 0.0565 0.85 90 1.1392 0.9495 0.0879 0.85 102 -1.4988 1.0011 0.1127 0.85 186 -2.1321 1.1025 0.1575 0.85 198 0.9031 1.0831 0.072 0.95 234 -1.2083 0.8682 0.0926 0.95 246 0.0596 0.7978 0.0303 0.95 258 -0.4461 0.9194 0.0441