CLAS physics database search results Measurement E151M2417 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.75 198 -0.8346 1.2291 0.0675 0.75 270 -0.5289 0.9 0.0487 0.85 102 -2.0399 0.9825 0.1509 0.85 114 -0.4525 0.8908 0.0445 0.85 186 -0.6412 1.1784 0.0553 0.85 198 -1.603 0.8969 0.12 0.85 210 -0.1912 1.1162 0.033 0.85 270 0.4796 1.0669 0.0459