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GenericMassGenerator.icc
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GenericMassGenerator.icc
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// -*- C++ -*-
//
// GenericMassGenerator.icc is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2007 The Herwig Collaboration
//
// Herwig++ is licenced under version 2 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
//
// This is the implementation of the inlined member functions of
// the GenericMassGenerator class.
//
namespace Herwig {
using namespace ThePEG;
inline GenericMassGenerator::GenericMassGenerator()
: _maxwgt(),_BWshape(0),_ngenerate(100),
_lowermass(),_uppermass(),
_mass(),_width(),
_mass2(),_mwidth(),
_ninitial(1000),
_initialize(false), _widthopt(false) {}
inline IBPtr GenericMassGenerator::clone() const {
return new_ptr(*this);
}
inline IBPtr GenericMassGenerator::fullclone() const {
return new_ptr(*this);
}
// generate the mass (default from ThePEG)
inline Energy GenericMassGenerator::mass(const ParticleData & in) const {
return mass(in,_lowermass,_uppermass);
}
// generate mass with limits
inline Energy GenericMassGenerator::mass(const ParticleData & in,
Energy low, Energy upp) const {
if(upp<low) return low;
Energy output;
int ntry=0; double wgt=0.;
do {
++ntry;
output=mass(wgt,in,low,upp,3);
if(wgt>_maxwgt) _maxwgt=wgt;
}
while(_maxwgt*(UseRandom::rnd())>wgt&&ntry<_ngenerate);
return (ntry>=_ngenerate) ? _mass : output;
}
// return the mass with a weight
inline Energy GenericMassGenerator::mass(double & wgt, const ParticleData &in,
double r) const {
return mass(wgt,in,_lowermass,_uppermass,r);
}
inline Energy GenericMassGenerator::mass(double & wgt, const ParticleData &in,
int shape,double r) const {
return mass(wgt,in,_lowermass,_uppermass,shape,r);
}
inline Energy GenericMassGenerator::mass(double & wgt,const ParticleData &in,
const Energy low,const Energy upp,
double r) const {
return mass(wgt,in,low,upp,_BWshape,r);
}
// member that does the work
inline Energy GenericMassGenerator::mass(double & wgt,const ParticleData &,
const Energy low,const Energy upp,
int shape, double r) const {
// calculate the mass square using fixed width BW
Energy lo=max(low,_lowermass),up=min(upp,_uppermass);
double rhomin=atan((lo*lo-_mass2)/_mwidth);
double rhomax=atan((up*up-_mass2)/_mwidth)-rhomin;
double rho=rhomin+rhomax*r;
Energy2 q2 = _mass2+_mwidth*tan(rho);
Energy q = sqrt(q2);
wgt = rhomax*weight(q,shape);
// return the mass
return q;
}
inline Energy GenericMassGenerator::lowerLimit() const {
return _lowermass;
}
inline Energy GenericMassGenerator::upperLimit() const {
return _uppermass;
}
inline Energy GenericMassGenerator::nominalMass() const {
return _mass;
}
inline Energy GenericMassGenerator::nominalWidth() const {
return _width;
}
inline double GenericMassGenerator::weight(Energy q) const {
return weight(q,_BWshape);
}
inline double GenericMassGenerator::weight(Energy q,int shape) const {
Energy2 q2 = q*q;
Energy4 sq=sqr(q2-_mass2);
Energy gam=width(q);
// finish the calculation of the width
Energy2 num;
if(shape==2) num = _mass*gam;
else if(shape==3) num = _mass*_width;
else num = q*gam;
Energy4 den = (shape==2) ? sq+_mass2*gam*gam : sq+q2*gam*gam;
return num/den*(sq+_mwidth*_mwidth)/Constants::pi/_mwidth;
}
inline Energy GenericMassGenerator::width(Energy q) const {
return (_BWshape==1||!_widthgen) ?
_width : _widthgen->width(*_particle,q);
}
inline tcPDPtr GenericMassGenerator::particle() const {
return _particle;
}
}

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