Today's ROOT function of the day is: 
void FitSlicesY(TF1 *f1, Int_t binmin, Int_t binmax, Int_t cut, Option_t *option)
 Project slices along Y in case of a 2-D histogram, then fit each slice
 with function f1 and make a histogram for each fit parameter
 Only bins along X between binmin and binmax are considered.
 if f1=0, a gaussian is assumed