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EvtBreitWignerPdf.cpp
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EvtBreitWignerPdf.cpp
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#include "EvtGenBase/EvtPatches.hh"
/*******************************************************************************
* Project: BaBar detector at the SLAC PEP-II B-factory
* Package: EvtGenBase
* File: $Id: EvtBreitWignerPdf.cpp,v 1.3 2009-03-16 15:55:55 robbep Exp $
* Author: Alexei Dvoretskii, dvoretsk@slac.stanford.edu, 2001-2002
*
* Copyright (C) 2002 Caltech
*******************************************************************************/
// Breit-Wigner shape PDF. If the width is zero it degenerates into a delta
// function. The integral and its inverse can be still evaluated.
#include <assert.h>
#include <stdio.h>
#include <math.h>
#include "EvtGenBase/EvtPatches.hh"
#include "EvtGenBase/EvtBreitWignerPdf.hh"
#include "EvtGenBase/EvtConst.hh"
EvtBreitWignerPdf::EvtBreitWignerPdf(double min, double max, double m0, double g0)
: EvtIntegPdf1D(min,max), _m0(m0), _g0(g0)
{}
EvtBreitWignerPdf::EvtBreitWignerPdf(const EvtBreitWignerPdf& other)
: EvtIntegPdf1D(other), _m0(other._m0), _g0(other._g0)
{}
EvtBreitWignerPdf::~EvtBreitWignerPdf()
{}
double EvtBreitWignerPdf::pdf(const EvtPoint1D& x) const
{
double m = x.value();
if((0 == (m - _m0)) && (0. == _g0)) {
printf("Delta function Breit-Wigner\n");
assert(0);
}
double ret = _g0/EvtConst::twoPi/((m-_m0)*(m-_m0)+_g0*_g0/4);
return ret;
}
double EvtBreitWignerPdf::pdfIntegral(double m) const
{
double itg = 0;
if(_g0 == 0) {
if(m > _m0) itg = 1.;
else
if(m < _m0) itg = 0.;
else
itg = 0.5;
}
else itg = atan((m-_m0)/(_g0/2.))/EvtConst::pi + 0.5;
return itg;
}
double EvtBreitWignerPdf::pdfIntegralInverse(double x) const
{
if(x < 0 || x > 1) {
printf("Invalid integral value %f\n",x);
assert(0);
}
double m = _m0;
if(_g0 != 0) m = _m0 + (_g0/2.)*tan(EvtConst::pi*(x-0.5));
return m;
}

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