CLAS physics database search results Measurement E151M3576 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.85 234 0.4087 0.2296 0.0311 0.85 246 -0.0677 0.2563 0.03 0.85 258 -0.4472 0.2254 0.0313 0.95 234 -0.3527 0.2566 0.0308 0.95 306 0.1254 0.2649 0.0301