1. Background Subtraction Fitting technique: Fit mass with G 1 + G 2 + a + b/x Background is G 1 + a + b/x Use 3  cut Goal: put limit on systematic error

2. Problems with Fits 1. Low mass background 2. High mass background

3. 1. Low mass background TDC cut can help No TDC cutTDC cut Background reduced

4. 2. High mass background No solution yet Other functions tried: G + G + a + b/x +c/x 2 G + G + a + bx +cx 2 G + G + a + bx G + G + exp(a + bx) Other techniques tried: bound parameters change range of fit better worse

5. Results G  = 41.5 G  = 46.5 3% shift 11% shift 0.5% shift

6. -t dependence G  = 41.5G  = 46.5

7. A N -t dependence G  = 41.5G  = 46.5

8. -t dependence of background G  = 46.5 G  = 41.5

9. Unpolarized beam G  = 46.5 -t dependence