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ThreeBodyAllOn1IntegralCalculator.tcc
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// -*- C++ -*-
//
// ThreeBodyAllOn1IntegralCalculator.tcc is a part of Herwig - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2019 The Herwig Collaboration
//
// Herwig is licenced under version 3 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
//
// This is the implementation of the non-inlined templated member
// functions of the ThreeBodyAllOn1IntegralCalculator class.
//
namespace Herwig{
using namespace ThePEG;
template <class T>
Energy ThreeBodyAllOn1IntegralCalculator<T>::operator() (double x) const {
Energy2 scale;
if(_intmass>ZERO) scale = _intmass*(_intmass+_intwidth*tan(x));
else scale = UnitRemoval::E2 * pow(x,1./(_intpower + 1.));
InvEnergy output=_theDgamma.threeBodydGammads(_mode,_m2[0],scale,_m[1],_m[2],_m[3]);
// the jacobian
InvEnergy2 term;
Energy2 rm2,rw2;
if(_intmass>ZERO) {
rm2 = sqr(_intmass);
rw2 = sqr(_intwidth);
term = _intmass*_intwidth / (sqr(scale-rm2) + rw2 * rm2);
}
else {
term = UnitRemoval::InvE2 * (_intpower+1.)*pow(scale * UnitRemoval::InvE2, _intpower);
}
return output/term;
}
template <class T>
Energy ThreeBodyAllOn1IntegralCalculator<T>::partialWidth(Energy2 scale) const {
_m2[0]=scale;
_m[0]=sqrt(scale);
// limits for the outer integral
Energy2 upp=ZERO,low=ZERO;
switch(_variabletype) {
case 1:
upp = (_m[0]-_m[3])*(_m[0]-_m[3]);
low = (_m[1]+_m[2])*(_m[1]+_m[2]);
break;
case 2:
upp = (_m[0]-_m[2])*(_m[0]-_m[2]);
low = (_m[1]+_m[3])*(_m[1]+_m[3]);
break;
case 3:
upp = (_m[0]-_m[1])*(_m[0]-_m[1]);
low = (_m[2]+_m[3])*(_m[2]+_m[3]);
break;
}
double rupp, rlow;
// transform them
if(_intmass>ZERO) {
rupp = atan2((upp-_intmass*_intmass), _intmass*_intwidth);
rlow = atan2((low-_intmass*_intmass), _intmass*_intwidth);
}
else {
rupp = pow(upp * UnitRemoval::InvE2, _intpower+1.);
rlow = pow(low * UnitRemoval::InvE2, _intpower+1.);
}
return _integrator.value(*this,rlow,rupp);
}
}

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