ROOT   Reference Guide
rf209_anaconv.py
Go to the documentation of this file.
1## \file
2## \ingroup tutorial_roofit
3## \notebook
4##
5## Addition and convolution: decay function p.d.fs with optional B physics effects (mixing
6## and CP violation) that can be analytically convolved with e.g. Gaussian resolution functions
7##
8## 
9## pdf1 = decay(t,tau) (x) delta(t)
10## pdf2 = decay(t,tau) (x) gauss(t,m,s)
11## pdf3 = decay(t,tau) (x) (f*gauss1(t,m1,s1) + (1-f)*gauss2(t,m1,s1))
12## 
13##
14## \macro_code
15##
16## \date February 2018
17## \authors Clemens Lange, Wouter Verkerke (C++ version)
18
19import ROOT
20
21# B-physics pdf with truth resolution
22# ---------------------------------------------------------------------
23
24# Variables of decay p.d.f.
25dt = ROOT.RooRealVar("dt", "dt", -10, 10)
26tau = ROOT.RooRealVar("tau", "tau", 1.548)
27
28# Build a truth resolution model (delta function)
29tm = ROOT.RooTruthModel("tm", "truth model", dt)
30
31# Construct decay(t) (x) delta(t)
32decay_tm = ROOT.RooDecay("decay_tm", "decay", dt,
33 tau, tm, ROOT.RooDecay.DoubleSided)
34
35# Plot p.d.f. (dashed)
36frame = dt.frame(ROOT.RooFit.Title("Bdecay (x) resolution"))
37decay_tm.plotOn(frame, ROOT.RooFit.LineStyle(ROOT.kDashed))
38
39# B-physics pdf with Gaussian resolution
40# ----------------------------------------------------------------------------
41
42# Build a gaussian resolution model
43bias1 = ROOT.RooRealVar("bias1", "bias1", 0)
44sigma1 = ROOT.RooRealVar("sigma1", "sigma1", 1)
45gm1 = ROOT.RooGaussModel("gm1", "gauss model 1", dt, bias1, sigma1)
46
47# Construct decay(t) (x) gauss1(t)
48decay_gm1 = ROOT.RooDecay("decay_gm1", "decay",
49 dt, tau, gm1, ROOT.RooDecay.DoubleSided)
50
51# Plot p.d.f.
52decay_gm1.plotOn(frame)
53
54# B-physics pdf with double Gaussian resolution
55# ------------------------------------------------------------------------------------------
56
57# Build another gaussian resolution model
58bias2 = ROOT.RooRealVar("bias2", "bias2", 0)
59sigma2 = ROOT.RooRealVar("sigma2", "sigma2", 5)
60gm2 = ROOT.RooGaussModel("gm2", "gauss model 2", dt, bias2, sigma2)
61
62# Build a composite resolution model f*gm1+(1-f)*gm2
63gm1frac = ROOT.RooRealVar("gm1frac", "fraction of gm1", 0.5)
65 "gmsum",
66 "sum of gm1 and gm2",
67 ROOT.RooArgList(
68 gm1,
69 gm2),
70 ROOT.RooArgList(gm1frac))
71
72# Construct decay(t) (x) (f*gm1 + (1-f)*gm2)
73decay_gmsum = ROOT.RooDecay(
74 "decay_gmsum", "decay", dt, tau, gmsum, ROOT.RooDecay.DoubleSided)
75
76# Plot p.d.f. (red)
77decay_gmsum.plotOn(frame, ROOT.RooFit.LineColor(ROOT.kRed))
78
79# Draw all frames on canvas
80c = ROOT.TCanvas("rf209_anaconv", "rf209_anaconv", 600, 600)