HybridCalculatorOriginal.cxx File Reference

#include "RooDataHist.h"
#include "RooDataSet.h"
#include "RooGlobalFunc.h"
#include "RooNLLVar.h"
#include "RooRealVar.h"
#include "RooAbsData.h"
#include "RooWorkspace.h"
#include "TH1.h"
#include "RooStats/HybridCalculatorOriginal.h"

Go to the source code of this file.

Functions
	ClassImp (RooStats::HybridCalculatorOriginal) using namespace RooStats

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Function Documentation

ClassImp

(

RooStats::HybridCalculatorOriginal

)

HybridCalculatorOriginal class: this class is a fresh rewrite in RooStats of RooStatsCms/LimitCalculator developped by D. Piparo and G. Schott Authors: D. Piparo, G. Schott - Universitaet Karlsruhe

The class is born from the need to have an implementation of the CLs method that could take advantage from the RooFit Package. The basic idea is the following:

• Instantiate an object specifying a signal+background model, a background model and a dataset.
• Perform toy MC experiments to know the distributions of -2lnQ
• Calculate the CLsb and CLs values as "integrals" of these distributions.

The class allows the user to input models as RooAbsPdf ( TH1 object could be used by using the RooHistPdf class) The pdfs must be "extended": for more information please refer to http://roofit.sourceforge.net). The dataset can be entered as a RooAbsData objects.

Unlike the TLimit Class a complete MC generation is performed at each step and not a simple Poisson fluctuation of the contents of the bins. Another innovation is the treatment of the nuisance parameters. The user can input in the constructor nuisance parameters. To include the information that we have about the nuisance parameters a prior PDF (RooAbsPdf) should be specified

Different test statistic can be used (likelihood ratio, number of events or profile likelihood ratio. The default is the likelihood ratio. See the method SetTestStatistic.

The number of toys to be generated is controlled by SetNumberOfToys(n).

The result of the calculations is returned as a HybridResult object pointer.

see also the following interesting references:

• Alex Read, "Presentation of search results: the CLs technique", Journal of Physics G: Nucl. Part. Phys. 28 2693-2704 (2002). see http://www.iop.org/EJ/abstract/0954-3899/28/10/313/

• Alex Read, "Modified Frequentist Analysis of Search Results (The CLs Method)" CERN 2000-005 (30 May 2000)

• V. Bartsch, G.Quast, "Expected signal observability at future experiments" CMS NOTE 2005/004

• http://root.cern.ch/root/html/src/TLimit.html

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