void Re_Smear()
{

gStyle->SetOptStat(2211);
gStyle->SetOptFit(1111);

/////////////////// Tree opening \\\\\\\\\\\\\\\

TFile *file1=TFile::Open("Analysis.root");
TTree *tree1=(TTree*)file1->Get("Analysis");

TH1D*h1 = new TH1D("h1","h1", 101.0,39.5,140.5);

//Defining a TF1Convolution
    TF1Convolution *f_conv = new TF1Convolution("gaus(0)+gaus(3)", "gaus", 30.,150., true);
    TF1 *gaus_1=new TF1("gaus_1","gaus",30.,150.);
    TF1 *gaus_2=new TF1("gaus_2","gaus",30.,150.);
    
f_conv->SetRange(30.,150.);
f_conv->SetNofPointsFFT(1000);


TF1 *f = new TF1("f", *f_conv, 40., 140., f_conv->GetNpar());
f->SetParameters(1e3,90.,13., 1e3 ,100.,30., 1.,0.,3.5);
    
    f->SetParNames("A_{1}","#mu_{1}","#sigma_{1}","A_{2}","#mu_{2}","#sigma_{2}","Amplitude Convolution","#mu_conv","#sigma_res");

    // I set the amplitude of the 2 gaussian to be positive
    f->SetParLimits(0,0.,1e6);
    f->SetParLimits(3,0.,1e6);
    
    // I set the mean  of the 2 gaussian to be between 60 and 120
    f->SetParLimits(1,60.,120.);
    f->SetParLimits(4,60.,120.);
    
    // I set the sigma  of the 2 gaussian to be between 0 and 100
    f->SetParLimits(2,1.,40.);
    f->SetParLimits(5,1.,40.);
    
// i fix the parameters of the convoluted gaussian
f->FixParameter(6,1.);
f->FixParameter(7,0.);
f->FixParameter(8,3.5);
    
    
    
TCanvas *c1 = new TCanvas("c1","Without constraint",800,600);
c1->Divide(2,2);
c1->cd(1);
tree1->Draw("M_Tot>>h1");

c1->cd(2);
h1->Draw("E1");
    h1->Fit(f,"ME");
    
    gaus_1->SetParameters(f->GetParameters());
    gaus_2->SetParameters(f->GetParameters()+3);
    
    gaus_1->SetParameter(0, 3.5*TMath::Sqrt(2*TMath::Pi())* gaus_1->GetParameter(0));
    gaus_2->SetParameter(0, 3.5*TMath::Sqrt(2*TMath::Pi())* gaus_2->GetParameter(0));
    gaus_1->SetLineColor(kBlue);
    gaus_2->SetLineColor(kBlue);
    gaus_1->Draw("same");
    gaus_2->Draw("same");
    
auto h2 = new TH1D("h2","h2_Mass_resolution",101.0,39.5,140.5);
h2 = (TH1D*)f->GetHistogram();
c1->cd(3);
gStyle->SetOptStat(2211);
gStyle->SetOptFit(111);
h2->Draw("E1");
}