CLAS physics database search results Measurement E151M2464 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.55 258 -0.2216 0.2474 0.0303 0.65 246 0.0014 0.2151 0.03 0.65 258 0.3658 0.2108 0.0309 0.65 270 -0.2399 0.2421 0.0304 0.75 258 0.209 0.2572 0.0303