CLAS physics database search results Measurement E19M20 E89-004 R. A. Schumacher 2005 cos(theta) Cz Data errors dimensionless dimensionless dimensionless -0.7 0.047 0.429 -0.4 0.098 0.471 -0.1 0.8 0.314 0.2 0.462 0.219 0.5 -0.1 0.188 0.8 -0.041 0.163