rf209_anaconv.py

# /
#
# 'ADDITION AND CONVOLUTION' ROOT.RooFit tutorial macro #209
#
# Decay function p.d.fs with optional B physics
# effects (mixing and CP violation) that can be
# analytically convolved with e.g. Gaussian resolution
# functions
#
# pdf1 = decay(t,tau) (x) delta(t)
# pdf2 = decay(t,tau) (x) gauss(t,m,s)
# pdf3 = decay(t,tau) (x) (f*gauss1(t,m1,s1) + (1-f)*gauss2(t,m1,s1))
#
# 07/2008 - Wouter Verkerke
#
# /


import ROOT


def rf209_anaconv():
    # B - p h y s i c s   p d f   w i t h   t r u t h   r e s o l u t i o n
    # ---------------------------------------------------------------------

    # Variables of decay p.d.f.
    dt = ROOT.RooRealVar("dt", "dt", -10, 10)
    tau = ROOT.RooRealVar("tau", "tau", 1.548)

    # Build a truth resolution model (delta function)
    tm = ROOT.RooTruthModel("tm", "truth model", dt)

    # Construct decay(t) (x) delta(t)
    decay_tm = ROOT.RooDecay("decay_tm", "decay", dt,
                             tau, tm, ROOT.RooDecay.DoubleSided)

    # Plot p.d.f. (dashed)
    frame = dt.frame(ROOT.RooFit.Title("Bdecay (x) resolution"))
    decay_tm.plotOn(frame, ROOT.RooFit.LineStyle(ROOT.kDashed))

    # B - p h y s i c s   p d f   w i t h   G a u s s i a n   r e s o l u t i o n
    # ----------------------------------------------------------------------------

    # Build a gaussian resolution model
    bias1 = ROOT.RooRealVar("bias1", "bias1", 0)
    sigma1 = ROOT.RooRealVar("sigma1", "sigma1", 1)
    gm1 = ROOT.RooGaussModel("gm1", "gauss model 1", dt, bias1, sigma1)

    # Construct decay(t) (x) gauss1(t)
    decay_gm1 = ROOT.RooDecay("decay_gm1", "decay",
                              dt, tau, gm1, ROOT.RooDecay.DoubleSided)

    # Plot p.d.f.
    decay_gm1.plotOn(frame)

    # B - p h y s i c s   p d f   w i t h   d o u b l e   G a u s s i a n   r e s o l u t i o n
    # ------------------------------------------------------------------------------------------

    # Build another gaussian resolution model
    bias2 = ROOT.RooRealVar("bias2", "bias2", 0)
    sigma2 = ROOT.RooRealVar("sigma2", "sigma2", 5)
    gm2 = ROOT.RooGaussModel("gm2", "gauss model 2", dt, bias2, sigma2)

    # Build a composite resolution model f*gm1+(1-f)*gm2
    gm1frac = ROOT.RooRealVar("gm1frac", "fraction of gm1", 0.5)
    gmsum = ROOT.RooAddModel(
        "gmsum", "sum of gm1 and gm2", ROOT.RooArgList(gm1, gm2), ROOT.RooArgList(gm1frac))

    # Construct decay(t) (x) (f*gm1 + (1-f)*gm2)
    decay_gmsum = ROOT.RooDecay(
        "decay_gmsum", "decay", dt, tau, gmsum, ROOT.RooDecay.DoubleSided)

    # Plot p.d.f. (red)
    decay_gmsum.plotOn(frame, ROOT.RooFit.LineColor(ROOT.kRed))

    # Draw all frames on canvas
    c = ROOT.TCanvas("rf209_anaconv", "rf209_anaconv", 600, 600)
    ROOT.gPad.SetLeftMargin(0.15)
    frame.GetYaxis().SetTitleOffset(1.6)
    frame.Draw()

    c.SaveAs("rf209_anaconv.png")


if __name__ == "__main__":
    rf209_anaconv()