//Breit-Wigner + quadratic background function
Double_t f(Double_t* x, Double_t* par)
{
 //M=par[0], Gamma=par[1]  
 
  Double_t A = 2* sqrt(2)*par[0]*par[1]*sqrt(par[0]*par[0]*(par[0]*par[0]+par[1]*par[1]));
  Double_t B = 3.14159* sqrt(par[0]*par[0] + sqrt(par[0]*par[0]*(par[0]*par[0]+par[1]*par[1])));
  Double_t C = (x[0]*x[0]-par[0]*par[0])*(x[0]*x[0]-par[0]*par[0]) + par[0]*par[0]*par[1]*par[1];
  Double_t BW = par[2]*(A/B)/C;
  
  Double_t pol2 = par[3] + par[4] * x[0] + par[5] * x[0] * x[0];
  return BW+pol2;
}


void fit_GT_gamma_BW2() {

  TFile *f1 = new TFile("../Carbon_07192023_152610.root");
  TH1F* hist = (TH1F*)f1->Get("hEgamma_dc_c_eff");

  Float_t xmin = 430;
  Float_t xmax = 990;


TF1 *fit_func = new TF1("fit_func",f,xmin,xmax,6);
fit_func->SetParameter(0,700.0);   
fit_func->SetParameter(1,100.0);    
fit_func->SetParameter(2,1000.0);   
fit_func->SetParameter(3,1000.0);  
fit_func->SetParameter(4,-1.0);  
fit_func->SetParameter(5,0.009);  

hist->Fit("fit_func","R");

// Create a canvas for plotting
  TCanvas* canvas = new TCanvas("canvas", "Fitted Histogram", 800, 600);
  
  // Plot the histogram
  hist->Draw();

  // Plot the fit function
  fit_func->SetLineColor(kRed);
  fit_func->Draw("same");

  // Customize the plot appearance if needed
  gPad->SetGrid();
  gStyle->SetOptFit(111); // Show fit statistics on the plot

  // Save the plot as an image (optional)
  canvas->SaveAs("fit_result.png");

}