CLAS physics database search results Measurement E151M1225 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LL Stat. error Syst. error degrees 0.55 258 0.241 0.4878 0.0405 0.55 270 -0.249 0.5029 0.0411 0.65 246 -0.2532 0.4219 0.0414 0.65 258 0.2209 0.4396 0.039 0.65 270 -0.0714 0.5211 0.0311 0.75 186 0.4458 0.5063 0.0585 0.75 246 0.3592 0.5265 0.0504 0.75 258 -0.5616 0.4865 0.0701