import ROOT

ROOT.gROOT.SetStyle("Plain")

x = ROOT.RooRealVar("x", "x", -10, 10)
y = ROOT.RooRealVar("y", "y", -10, 10)
  
mux = ROOT.RooRealVar("mux", "average-x'", 0, -1, 1)
sigmax = ROOT.RooRealVar("sigmax", "sigma-x'", 0.5, 0, 5)
gaussx = ROOT.RooGaussian("gaussx","gaussian PDF x'", x, mux, sigmax)
  
muy = ROOT.RooRealVar("muy", "average-y'", 0, -1, 1)
sigmay = ROOT.RooRealVar("sigmay", "sigma-y'", 1.5, 0, 5)
gaussy = ROOT.RooGaussian("gaussy","gaussian PDF y'", y, muy, sigmay)

gaussxy = ROOT.RooProdPdf("gaussxy", "gaussxy", ROOT.RooArgSet(gaussx, gaussy), ROOT.RooCmdArg())

c = ROOT.TCanvas()
h2 = gaussxy.createHistogram("h2", x, ROOT.RooFit.Binning(100), ROOT.RooFit.YVar(y, ROOT.RooFit.Binning(100)))

h2.Draw("surf3")
c.SaveAs("03-pdfProduct.pdf")