import ROOT
from ROOT.RooFit import *
mes= ROOT.RooRealVar("mes","m_{ES} (GeV)",5.265,5.29);
mean=ROOT.RooRealVar("mean","B^{#pm} mass",5.28,5.265,5.29);
width=ROOT.RooRealVar("width","B^{#pm} width",0.0027,0.001,1.);
signal_g=ROOT.RooGaussian("signal_g","signal PDF",mes,mean,width);
bkg_g=ROOT.RooPolynomial("bkg_g","bkg_g",mes) 

nsig=ROOT.RooRealVar("nsig","#signal events",200,0.,1000);
nbkg=ROOT.RooRealVar("nbkg","#background events",40,0.,1000);
model_g=ROOT.RooAddPdf("model_g","g+a",ROOT.RooArgList(signal_g,bkg_g),ROOT.RooArgList(nsig,nbkg));
dataset= model_g.generate(ROOT.RooArgSet(mes),2000) 

sigma1=ROOT.RooRealVar ("sigma1", "sigma1", 0.0015,0.001,1);
sigma2=ROOT.RooRealVar("sigma2", "sigma2",0.0030,0.001,3);
alpha1=ROOT.RooRealVar ("alpha1", "alpha1", 1.5, 0,10);
alpha2=ROOT.RooRealVar ("alpha2", "alpha2", 1.5, 0,10);
n=ROOT.RooRealVar("n", "n", 1.0,0,20);
ratio=ROOT.RooRealVar("ratio", "ratio", 0.1, 0, 1);
p0=ROOT.RooRealVar("p0", "p0", 0.0, 0, 2.0);
N=200
a0=ROOT.RooRealVar ("a0", "a0", 0.166, -100, 100);
a1=ROOT.RooRealVar ("a1", "a1", -0.0027, -10, 10);

bkg=ROOT.RooChebychev("bkg","bkg",mes,ROOT.RooArgList(a0,a1))
myCB1=ROOT.RooCBShape ("CBMass1", "CBMass1", mes, mean, sigma1, alpha1, n);
myCB2=ROOT.RooCBShape ("CBMass2", "CBMass2", mes, mean, sigma2, alpha2, n);
signal=ROOT.RooAddPdf ("signal", "signal", ROOT.RooArgList(myCB1, myCB2), ROOT.RooArgList(ratio));

Nsig= ROOT.RooRealVar ("Nsig", "yield of signal", 200,0.,2000);
Nbkg=  ROOT.RooRealVar("Nbkg", "yield of background",40,0.,2000);
model=  ROOT.RooAddPdf ("model", "signal and background", ROOT.RooArgList(signal, bkg), ROOT.RooArgList(Nsig, Nbkg)); 

r = model.fitTo(dataset) ;

frame=mes.frame(200)
dataset.plotOn(frame, ROOT.RooFit.MarkerStyle ( 20 ),ROOT.RooFit.Binning(200) )
model.plotOn(frame,ROOT.RooFit.Name('signal'),ROOT.RooFit.DrawOption("F"), ROOT.RooFit.FillStyle (1001),ROOT.RooFit.FillColor(ROOT.kRed ), ROOT.RooFit.Components("signal") )#,Components="background")
model.plotOn(frame,ROOT.RooFit.Name("bkg"),ROOT.RooFit.DrawOption("F"), ROOT.RooFit.FillStyle (1001),ROOT.RooFit.FillColor(ROOT.kBlue ), ROOT.RooFit.Components("bkg") )#,Components="background")