rf312_multirangefit.py

#####################################
#
# 'MULTIDIMENSIONAL MODELS' ROOT.RooFit tutorial macro #312
#
# Performing fits in multiple (disjoint) ranges in one or more dimensions
#
#
#
# 07/2008 - Wouter Verkerke
#
# /


import ROOT


def rf312_multirangefit():

    # C r e a t e   2 D   p d f   a n d   d a t a
    # -------------------------------------------

    # Define observables x,y
    x = ROOT.RooRealVar("x", "x", -10, 10)
    y = ROOT.RooRealVar("y", "y", -10, 10)

    # Construct the signal pdf gauss(x)*gauss(y)
    mx = ROOT.RooRealVar("mx", "mx", 1, -10, 10)
    my = ROOT.RooRealVar("my", "my", 1, -10, 10)

    gx = ROOT.RooGaussian("gx", "gx", x, mx, ROOT.RooFit.RooConst(1))
    gy = ROOT.RooGaussian("gy", "gy", y, my, ROOT.RooFit.RooConst(1))

    sig = ROOT.RooProdPdf("sig", "sig", gx, gy)

    # Construct the background pdf (flat in x,y)
    px = ROOT.RooPolynomial("px", "px", x)
    py = ROOT.RooPolynomial("py", "py", y)
    bkg = ROOT.RooProdPdf("bkg", "bkg", px, py)

    # Construct the composite model sig+bkg
    f = ROOT.RooRealVar("f", "f", 0., 1.)
    model = ROOT.RooAddPdf("model", "model", ROOT.RooArgList(sig, bkg), ROOT.RooArgList(f))

    # Sample 10000 events in (x,y) from the model
    modelData = model.generate(ROOT.RooArgSet(x, y), 10000)

    # D e f i n e   s i g n a l   a n d   s i d e b a n d   r e g i o n s
    # -------------------------------------------------------------------

    # Construct the SideBand1,SideBand2, regions
    #
    #                    |
    #      +-------------+-----------+
    #      |             |           |
    #      |    Side     |   Sig     |
    #      |    Band1    |   nal     |
    #      |             |           |
    #    --+-------------+-----------+--
    #      |                         |
    #      |           Side          |
    #      |           Band2         |
    #      |                         |
    #      +-------------+-----------+
    #                    |

    x.setRange("SB1", -10, +10)
    y.setRange("SB1", -10, 0)

    x.setRange("SB2", -10, 0)
    y.setRange("SB2", 0, +10)

    x.setRange("SIG", 0, +10)
    y.setRange("SIG", 0, +10)

    x.setRange("FULL", -10, +10)
    y.setRange("FULL", -10, +10)

    # P e r f o r m   f i t s   i n   i n d i v i d u a l   s i d e b a n d   r e g i o n s
    # -------------------------------------------------------------------------------------

    # Perform fit in SideBand1 region (ROOT.RooAddPdf coefficients will be
    # interpreted in full range)
    r_sb1 = model.fitTo(modelData, ROOT.RooFit.Range(
        "SB1"), ROOT.RooFit.Save())

    # Perform fit in SideBand2 region (ROOT.RooAddPdf coefficients will be
    # interpreted in full range)
    r_sb2 = model.fitTo(modelData, ROOT.RooFit.Range(
        "SB2"), ROOT.RooFit.Save())

    # P e r f o r m   f i t s   i n   j o i n t    s i d e b a n d   r e g i o n s
    # -----------------------------------------------------------------------------

    # Now perform fit to joint 'L-shaped' sideband region 'SB1|SB2'
    # (ROOT.RooAddPdf coefficients will be interpreted in full range)
    r_sb12 = model.fitTo(modelData, ROOT.RooFit.Range(
        "SB1,SB2"), ROOT.RooFit.Save())

    # Print results for comparison
    r_sb1.Print()
    r_sb2.Print()
    r_sb12.Print()


if __name__ == "__main__":
    rf312_multirangefit()