Fit Type B:  Fit the mass peak for the signal region definition
Obtain the error on the signal region definition from that fit:
Mean: 3.09327
Sigma:0.0158644
Norm: 48222.1
Signal fraction: 0.909957+/-0.00037941
The fitted value of tau:     0.044024+/-0.000735684
The fitted value of Lambda+: 0.0689839+/-0.0024139
The fitted value of Lambda-: 0.0715927+/-0.00228316
The fitted value of F+:      0.12036+/-0.00355418
The fitted value of F-:      0.0849113+/-0.00273029
The fitted value of Scale:   1.04605+/-0.00417494
The fitted value of alpha:   0.909567+/-0.000378023
The fitted value of Bfrac:   0.165608+/-0.00221811