CLAS physics database search results Measurement E19M18 E89-004 R. A. Schumacher 2005 cos(theta) Cz Data errors dimensionless dimensionless dimensionless -0.7 1.279 0.444 -0.4 0.7 0.434 -0.1 0.958 0.284 0.2 0.235 0.208 0.5 -0.818 0.182 0.8 -0.134 0.17