Double_t background1(Double_t *x, Double_t *par) {
   return par[0] + par[1]*x[0] ;
}

Double_t GaussianPeak(Double_t *x, Double_t *par) {
   
    Double_t arg = 0;
    if (par[2]!=0) arg = (x[0] - par[2])/par[3];
    return par[4]*TMath::Exp(-0.5*arg*arg);

}


Double_t background2(Double_t *x, Double_t *par) {
   return par[5] + par[6]*x[0] ;
}


// Sum of background and peak function
Double_t fitFunction(Double_t *x, Double_t *par) {
   return background1(x,par) + GaussianPeak(x,&par[2]) + background2(x,&par[5]);
}







void signal_back()
{
TFile *f = TFile::Open("h_deltavz_tdiff_12736.root","read");
TH1F *his = (TH1F*) f->Get("delvz_tdiff");
his  ->GetXaxis()-> SetRangeUser(-110,110);
    
TF1 *fitFcn = new TF1("fitFcn",fitFunction,-110,110,7);
    
 his->Fit("fitFcn");


}