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diff --git a/Decay/DecayPhaseSpaceChannel.cc b/Decay/DecayPhaseSpaceChannel.cc
--- a/Decay/DecayPhaseSpaceChannel.cc
+++ b/Decay/DecayPhaseSpaceChannel.cc
@@ -1,589 +1,590 @@
// -*- C++ -*-
//
// DecayPhaseSpaceChannel.cc is a part of Herwig++ - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2011 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 non-inlined, non-templated member
// functions of the DecayPhaseSpaceChannel class.
//
// Author: Peter Richardson
//
#include "DecayPhaseSpaceChannel.h"
#include "DecayPhaseSpaceMode.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Repository/CurrentGenerator.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Interface/ParVector.h"
#include "ThePEG/Interface/RefVector.h"
#include "ThePEG/Interface/Switch.h"
#include <ThePEG/Repository/CurrentGenerator.h>
using namespace Herwig;
DecayPhaseSpaceChannel::DecayPhaseSpaceChannel(tcDecayPhaseSpaceModePtr in)
: _mode(in) {}
void DecayPhaseSpaceChannel::persistentOutput(PersistentOStream & os) const {
os << _intpart << _jactype << ounit(_intmass,GeV) << ounit(_intwidth,GeV)
<< ounit(_intmass2,GeV2) << ounit(_intmwidth,GeV2) << _intpower
<< _intdau1 << _intdau2 << _intext << _mode;
}
void DecayPhaseSpaceChannel::persistentInput(PersistentIStream & is, int) {
is >> _intpart >> _jactype >> iunit(_intmass,GeV) >> iunit(_intwidth,GeV)
>> iunit(_intmass2,GeV2) >> iunit(_intmwidth,GeV2) >> _intpower
>> _intdau1 >> _intdau2 >> _intext >> _mode;
}
ClassDescription<DecayPhaseSpaceChannel>
DecayPhaseSpaceChannel::initDecayPhaseSpaceChannel;
// Definition of the static class description member.
void DecayPhaseSpaceChannel::Init() {
static RefVector<DecayPhaseSpaceChannel,ParticleData> interfaceIntermediateParticles
("IntermediateParticles",
"The intermediate particles in the decay chain.",
&DecayPhaseSpaceChannel::_intpart, 0, false, false, true, false);
static ParVector<DecayPhaseSpaceChannel,int> interfacejactype
("Jacobian",
"The type of Jacobian to use for the intermediate particle",
&DecayPhaseSpaceChannel::_jactype,
0, 0, 0, 0, 1, false, false, true);
static ParVector<DecayPhaseSpaceChannel,double> interfaceIntermediatePower
("IntermediatePower",
"The power to use in the Jacobian",
&DecayPhaseSpaceChannel::_intpower,
0, 0, 0, -10, 10, false, false, true);
static ParVector<DecayPhaseSpaceChannel,int> interfaceIntermediateDau1
("IntermediateDaughter1",
"First Daughter of the intermediate",
&DecayPhaseSpaceChannel::_intdau1,
0, 0, 0, -10, 10, false, false, true);
static ParVector<DecayPhaseSpaceChannel,int> interfaceIntermediateDau2
("IntermediateDaughter2",
"Second Daughter of the intermediate",
&DecayPhaseSpaceChannel::_intdau2,
0, 0, 0, -10, 10, false, false, true);
static ClassDocumentation<DecayPhaseSpaceChannel> documentation
("The DecayPhaseSpaceChannel class defines a channel"
" for the multichannel integration of the phase space for a decay.");
}
// generate the momenta of the external particles
vector<Lorentz5Momentum>
DecayPhaseSpaceChannel::generateMomenta(const Lorentz5Momentum & pin,
const vector<Energy> & massext) {
// integers for loops
unsigned int ix,iy,idau[2],iz;
// storage of the momenta of the external particles
vector<Lorentz5Momentum> pexternal;
// and the internal particles
vector<Lorentz5Momentum> pinter;
// copy the momentum of the incoming particle
pexternal.push_back(pin); pinter.push_back(pin);
pexternal.resize(_mode->numberofParticles());
pinter.resize(_intpart.size());
// masses of the intermediate particles
vector<Energy> massint(_intpart.size());
massint[0]=pin.mass();
// generate all the decays in the chain
Energy lower,upper,lowerb[2];
for(ix=0;ix<_intpart.size();++ix) {
idau[0] = abs(_intdau1[ix]);
idau[1] = abs(_intdau2[ix]);
// if both decay products off-shell
if(_intdau1[ix]<0&&_intdau2[ix]<0) {
// lower limits on the masses of the two resonances
for(iy=0;iy<2;++iy) {
lowerb[iy]=ZERO;
for(iz=0;iz<_intext[idau[iy]].size();++iz) {
lowerb[iy]+=massext[_intext[idau[iy]][iz]];
}
}
// randomize the order
if(UseRandom::rnd()<0.5) {
// mass of the first resonance
upper = massint[ix]-lowerb[1];
lower = lowerb[0];
massint[idau[0]]=generateMass(idau[0],lower,upper);
// mass of the second resonance
upper = massint[ix]-massint[idau[0]];
lower = lowerb[1];
massint[idau[1]]=generateMass(idau[1],lower,upper);
}
else {
// mass of the second resonance
upper = massint[ix]-lowerb[0];
lower = lowerb[1];
massint[idau[1]]=generateMass(idau[1],lower,upper);
// mass of the first resonance
upper = massint[ix]-massint[idau[1]];
lower = lowerb[0];
massint[idau[0]]=generateMass(idau[0],lower,upper);
}
// generate the momenta of the decay products
twoBodyDecay(pinter[ix],massint[idau[0]],massint[idau[1]],
pinter[idau[0]],pinter[idau[1]]);
}
// only first off-shell
else if(_intdau1[ix]<0) {
// compute the limits of integration
upper = massint[ix]-massext[idau[1]];
lower = ZERO;
for(iy=0;iy<_intext[idau[0]].size();++iy) {
lower+=massext[_intext[idau[0]][iy]];
}
massint[idau[0]]=generateMass(idau[0],lower,upper);
// generate the momenta of the decay products
twoBodyDecay(pinter[ix],massint[idau[0]],massext[idau[1]],
pinter[idau[0]],pexternal[idau[1]]);
}
// only second off-shell
else if(_intdau2[ix]<0) {
// compute the limits of integration
upper = massint[ix]-massext[idau[0]];
lower = ZERO;
for(iy=0;iy<_intext[idau[1]].size();++iy) {
lower+=massext[_intext[idau[1]][iy]];
}
massint[idau[1]]=generateMass(idau[1],lower,upper);
// generate the momenta of the decay products
twoBodyDecay(pinter[ix],massext[idau[0]],massint[idau[1]],
pexternal[idau[0]],pinter[idau[1]]);
}
// both on-shell
else {
// generate the momenta of the decay products
twoBodyDecay(pinter[ix],massext[idau[0]],massext[idau[1]],
pexternal[idau[0]],pexternal[idau[1]]);
}
}
// return the external momenta
return pexternal;
}
// generate the weight for this channel given a phase space configuration
double DecayPhaseSpaceChannel::generateWeight(const vector<Lorentz5Momentum> & output) {
using Constants::pi;
// integers for loops
unsigned int ix,iy,idau[2],iz;
// include the prefactor due to the weight of the channel
double wgt=1.;
// work out the masses of the intermediate particles
- vector<Energy2> intmass2(_intpart.size());
- vector<Energy> intmass(_intpart.size());
+ static vector<Energy2> intmass2;
+ static vector<Energy> intmass;
+ intmass.clear(); intmass2.clear();
Lorentz5Momentum pinter;
for(ix=0;ix<_intpart.size();++ix) {
pinter=output[_intext[ix][0]];
for(iz=1;iz<_intext[ix].size();++iz) pinter+=output[_intext[ix][iz]];
pinter.rescaleMass();
- intmass[ix] = pinter.mass();
- intmass2[ix] = sqr(intmass[ix]);
+ intmass.push_back( pinter.mass() );
+ intmass2.push_back( sqr(pinter.mass()) );
}
Energy2 scale(intmass2[0]);
// calculate the terms for each of the decays
Energy lower,upper,lowerb[2];
for(ix=0;ix<_intpart.size();++ix) {
idau[0] = abs(_intdau1[ix]);
idau[1] = abs(_intdau2[ix]);
// if both decay products off-shell
Energy pcm;
if(_intdau1[ix]<0&&_intdau2[ix]<0) {
// lower limits on the masses of the two resonances
for(iy=0;iy<2;++iy) {
lowerb[iy]=ZERO;
for(iz=0;iz<_intext[idau[iy]].size();++iz)
lowerb[iy]+=output[_intext[idau[iy]][iz]].mass();
}
// undo effect of randomising
// weight for the first order
// contribution of first resonance
upper = intmass[ix]-lowerb[1];
lower = lowerb[0];
InvEnergy2 wgta=massWeight(idau[0],intmass[idau[0]],lower,upper);
// contribution of second resonance
upper = intmass[ix]-intmass[idau[0]];
lower = lowerb[1];
InvEnergy4 wgta2 = wgta*massWeight(idau[1],intmass[idau[1]],lower,upper);
// weight for the second order
upper = intmass[ix]-lowerb[0];
lower = lowerb[1];
InvEnergy2 wgtb=massWeight(idau[1],intmass[idau[1]],lower,upper);
upper = intmass[ix]-intmass[idau[1]];
lower = lowerb[0];
InvEnergy4 wgtb2=wgtb*massWeight(idau[0],intmass[idau[0]],lower,upper);
// weight factor
wgt *=0.5*sqr(scale)*(wgta2+wgtb2);
// factor for the kinematics
pcm = Kinematics::pstarTwoBodyDecay(intmass[ix],intmass[idau[0]],
intmass[idau[1]]);
wgt *= intmass[ix]*8.*pi*pi/pcm;
}
// only first off-shell
else if(_intdau1[ix]<0) {
// compute the limits of integration
upper = intmass[ix]-output[idau[1]].mass();
lower = ZERO;
for(iy=0;iy<_intext[idau[0]].size();++iy)
lower+=output[_intext[idau[0]][iy]].mass();
wgt *=scale*massWeight(idau[0],intmass[idau[0]],lower,upper);
pcm = Kinematics::pstarTwoBodyDecay(intmass[ix],intmass[idau[0]],
output[idau[1]].mass());
wgt *= intmass[ix]*8.*pi*pi/pcm;
}
// only second off-shell
else if(_intdau2[ix]<0) {
// compute the limits of integration
upper = intmass[ix]-output[idau[0]].mass();
lower = ZERO;
for(iy=0;iy<_intext[idau[1]].size();++iy)
lower+=output[_intext[idau[1]][iy]].mass();
wgt *=scale*massWeight(idau[1],intmass[idau[1]],lower,upper);
pcm = Kinematics::pstarTwoBodyDecay(intmass[ix],intmass[idau[1]],
output[idau[0]].mass());
wgt *=intmass[ix]*8.*pi*pi/pcm;
}
// both on-shell
else {
pcm = Kinematics::pstarTwoBodyDecay(intmass[ix],output[idau[1]].mass(),
output[idau[0]].mass());
wgt *=intmass[ix]*8.*pi*pi/pcm;
}
}
// finally the overall factor
wgt /= pi;
// return the answer
return wgt;
}
// output the information to a stream
ostream & Herwig::operator<<(ostream & os, const DecayPhaseSpaceChannel & channel) {
// output of the external particles
os << "Channel for the decay of " << channel._mode->externalParticles(0)->PDGName()
<< " -> ";
for(unsigned int ix=1;ix<channel._mode->numberofParticles();++ix)
os << channel._mode->externalParticles(ix)->PDGName() << " ";
os << endl;
os << "Decay proceeds in following steps ";
for(unsigned int ix=0;ix<channel._intpart.size();++ix) {
os << channel._intpart[ix]->PDGName() << " -> ";
if(channel._intdau1[ix]>0) {
os << channel._mode->externalParticles(channel._intdau1[ix])->PDGName()
<< "(" << channel._intdau1[ix]<< ") ";
}
else {
os << channel._intpart[-channel._intdau1[ix]]->PDGName()
<< "(" << channel._intdau1[ix]<< ") ";
}
if(channel._intdau2[ix]>0) {
os << channel._mode->externalParticles(channel._intdau2[ix])->PDGName()
<< "(" <<channel._intdau2[ix] << ") ";
}
else{
os << channel._intpart[-channel._intdau2[ix]]->PDGName()
<< "(" <<channel._intdau2[ix] << ") ";
}
os << endl;
}
return os;
}
// doinit method
void DecayPhaseSpaceChannel::doinit() {
Interfaced::doinit();
// check if the mode pointer exists
if(!_mode){throw InitException() << "DecayPhaseSpaceChannel::doinit() the "
<< "channel must have a pointer to a decay mode "
<< Exception::abortnow;}
// masses and widths of the intermediate particles
for(unsigned int ix=0;ix<_intpart.size();++ix) {
_intmass.push_back(_intpart[ix]->mass());
_intwidth.push_back(_intpart[ix]->width());
_intmass2.push_back(_intpart[ix]->mass()*_intpart[ix]->mass());
_intmwidth.push_back(_intpart[ix]->mass()*_intpart[ix]->width());
}
// external particles for each intermediate particle
vector<int> temp;
_intext.resize(_intpart.size());
// loop over the intermediate particles
for(int ix=_intpart.size()-1;ix>=0;--ix) {
temp.clear();
// add the first daughter
if(_intdau1[ix]>=0) {
temp.push_back(_intdau1[ix]);
}
else {
int iy = -_intdau1[ix];
vector<int>::iterator istart=_intext[iy].begin();
vector<int>::iterator iend=_intext[iy].end();
for(;istart!=iend;++istart) temp.push_back(*istart);
}
// add the second daughter
if(_intdau2[ix]>=0) {
temp.push_back(_intdau2[ix]);
}
else {
int iy = -_intdau2[ix];
vector<int>::iterator istart=_intext[iy].begin();
vector<int>::iterator iend=_intext[iy].end();
for(;istart!=iend;++istart) temp.push_back(*istart);
}
_intext[ix]=temp;
}
// ensure intermediates either have the width set, or
// can't possibly be on-shell
Energy massmax;
if(_mode->testOnShell()) {
massmax = _mode->externalParticles(0)->mass();
for(unsigned int ix=1;ix<_mode->numberofParticles();++ix)
massmax -= _mode->externalParticles(ix)->mass();
}
else {
massmax = _mode->externalParticles(0)->massMax();
for(unsigned int ix=1;ix<_mode->numberofParticles();++ix)
massmax -= _mode->externalParticles(ix)->massMin();
}
for(unsigned int ix=0;ix<_intpart.size();++ix) {
if(_intwidth[ix]==ZERO && ix>0 && _jactype[ix]==0 ) {
Energy massmin(ZERO);
for(unsigned int iy=0;iy<_intext[ix].size();++iy)
massmin += _mode->testOnShell() ?
_mode->externalParticles(_intext[ix][iy])->mass() :
_mode->externalParticles(_intext[ix][iy])->massMin();
// check if can be on-shell
if(_intmass[ix]>=massmin&&_intmass[ix]<=massmax+massmin) {
string modeout;
for(unsigned int iy=0;iy<_mode->numberofParticles();++iy) {
modeout += _mode->externalParticles(iy)->PDGName() + " ";
}
throw InitException() << "Width zero for " << _intpart[ix]->PDGName()
<< " in DecayPhaseSpaceChannel::doinit() "
<< modeout
<< Exception::runerror;
}
}
}
}
void DecayPhaseSpaceChannel::doinitrun() {
Interfaced::doinitrun();
if(!_mode->testOnShell()) return;
_intmass.clear();
_intwidth.clear();
_intmass2.clear();
_intmwidth.clear();
// masses and widths of the intermediate particles
for(unsigned int ix=0;ix<_intpart.size();++ix) {
_intmass.push_back(_intpart[ix]->mass());
_intwidth.push_back(_intpart[ix]->width());
_intmass2.push_back(_intpart[ix]->mass()*_intpart[ix]->mass());
_intmwidth.push_back(_intpart[ix]->mass()*_intpart[ix]->width());
}
// ensure intermediates either have the width set, or
// can't possibly be on-shell
Energy massmax = _mode->externalParticles(0)->massMax();
for(unsigned int ix=1;ix<_mode->numberofParticles();++ix)
massmax -= _mode->externalParticles(ix)->massMin();
for(unsigned int ix=0;ix<_intpart.size();++ix) {
if(_intwidth[ix]==0.*MeV && ix>0 && _jactype[ix]==0 ) {
Energy massmin(0.*GeV);
for(unsigned int iy=0;iy<_intext[ix].size();++iy)
massmin += _mode->externalParticles(_intext[ix][iy])->massMin();
// check if can be on-shell
if(_intmass[ix]>=massmin&&_intmass[ix]<=massmax+massmin) {
string modeout;
for(unsigned int iy=0;iy<_mode->numberofParticles();++iy) {
modeout += _mode->externalParticles(iy)->PDGName() + " ";
}
throw Exception() << "Width zero for " << _intpart[ix]->PDGName()
<< " in DecayPhaseSpaceChannel::doinitrun() "
<< modeout
<< Exception::runerror;
}
}
}
}
// generate the final-state particles including the intermediate resonances
void DecayPhaseSpaceChannel::generateIntermediates(bool cc, const Particle & in,
ParticleVector & out) {
// integers for the loops
unsigned int ix,iz;
// create the particles
// incoming particle
ParticleVector external;
external.push_back(const_ptr_cast<tPPtr>(&in));
// outgoing
for(ix=0;ix<out.size();++ix) external.push_back(out[ix]);
out.clear();
// now create the intermediates
ParticleVector resonance;
resonance.push_back(external[0]);
PPtr respart;
tcPDPtr parttemp;
Lorentz5Momentum pinter;
for(ix=1;ix<_intpart.size();++ix) {
pinter=external[_intext[ix][0]]->momentum();
for(iz=1;iz<_intext[ix].size();++iz)
pinter+=external[_intext[ix][iz]]->momentum();
pinter.rescaleMass();
respart = (cc&&_intpart[ix]->CC()) ?
_intpart[ix]->CC()->produceParticle(pinter) :
_intpart[ix] ->produceParticle(pinter);
resonance.push_back(respart);
}
// set up the mother daughter relations
for(ix=1;ix<_intpart.size();++ix) {
resonance[ix]->addChild( _intdau1[ix]<0 ?
resonance[-_intdau1[ix]] : external[_intdau1[ix]]);
resonance[ix]->addChild( _intdau2[ix]<0 ?
resonance[-_intdau2[ix]] : external[_intdau2[ix]]);
if(resonance[ix]->dataPtr()->stable())
resonance[ix]->setLifeLength(Lorentz5Distance());
}
// construct the output with the particles in the first step
out.push_back( _intdau1[0]>0 ? external[_intdau1[0]] : resonance[-_intdau1[0]]);
out.push_back( _intdau2[0]>0 ? external[_intdau2[0]] : resonance[-_intdau2[0]]);
}
double DecayPhaseSpaceChannel::atanhelper_(int ires, Energy limit) {
return atan2( limit*limit-_intmass2[ires], _intmwidth[ires] );
}
// return the weight for a given resonance
InvEnergy2 DecayPhaseSpaceChannel::massWeight(int ires, Energy moff,
Energy lower,Energy upper) {
InvEnergy2 wgt = ZERO;
if(lower>upper) {
throw DecayPhaseSpaceError() << "DecayPhaseSpaceChannel::massWeight not allowed "
<< ires << " " << _intpart[ires]->id() << " "
<< moff/GeV << " " << lower/GeV << " " << upper/GeV << Exception::eventerror;
}
// use a Breit-Wigner
if ( _jactype[ires] == 0 ) {
double rhomin = atanhelper_(ires,lower);
double rhomax = atanhelper_(ires,upper) - rhomin;
if ( rhomax != 0.0 ) {
Energy2 moff2=moff*moff-_intmass2[ires];
wgt = _intmwidth[ires]/rhomax/(moff2*moff2+_intmwidth[ires]*_intmwidth[ires]);
}
else {
wgt = 1./((sqr(upper)-sqr(lower))*sqr(sqr(moff)-_intmass2[ires])/
(sqr(lower)-_intmass2[ires])/(sqr(upper)-_intmass2[ires]));
}
}
// power law
else if(_jactype[ires]==1) {
double rhomin = pow(sqr(lower/MeV),_intpower[ires]+1.);
double rhomax = pow(sqr(upper/MeV),_intpower[ires]+1.)-rhomin;
wgt = (_intpower[ires]+1.)/rhomax*pow(sqr(moff/MeV),_intpower[ires])
/MeV/MeV;
}
else if(_jactype[ires]==2) {
wgt = 1./Constants::pi/_intmwidth[ires];
}
else {
throw DecayPhaseSpaceError() << "Unknown type of Jacobian in "
<< "DecayPhaseSpaceChannel::massWeight"
<< Exception::eventerror;
}
return wgt;
}
Energy DecayPhaseSpaceChannel::generateMass(int ires,Energy lower,Energy upper) {
static const Energy eps=1e-9*MeV;
if(lower<eps) lower=eps;
Energy mass=ZERO;
if(lower>upper) throw DecayPhaseSpaceError() << "DecayPhaseSpaceChannel::generateMass"
<< " not allowed"
<< Exception::eventerror;
if(abs(lower-upper)/(lower+upper)>2e-10) {
lower +=1e-10*(lower+upper);
upper -=1e-10*(lower+upper);
}
else
return 0.5*(lower+upper);
// use a Breit-Wigner
if(_jactype[ires]==0) {
if(_intmwidth[ires]!=ZERO) {
Energy2 lower2 = sqr(lower);
Energy2 upper2 = sqr(upper);
double rhomin = atan2((lower2 - _intmass2[ires]),_intmwidth[ires]);
double rhomax = atan2((upper2 - _intmass2[ires]),_intmwidth[ires])-rhomin;
double rho = rhomin+rhomax*UseRandom::rnd();
Energy2 mass2 = max(lower2,min(upper2,_intmass2[ires]+_intmwidth[ires]*tan(rho)));
if(mass2<ZERO) mass2 = ZERO;
mass = sqrt(mass2);
}
else {
mass = sqrt(_intmass2[ires]+
(sqr(lower)-_intmass2[ires])*(sqr(upper)-_intmass2[ires])/
(sqr(lower)-_intmass2[ires]-UseRandom::rnd()*(sqr(lower)-sqr(upper))));
}
}
// use a power-law
else if(_jactype[ires]==1) {
double rhomin = pow(sqr(lower/MeV),_intpower[ires]+1.);
double rhomax = pow(sqr(upper/MeV),_intpower[ires]+1.)-rhomin;
double rho = rhomin+rhomax*UseRandom::rnd();
mass = pow(rho,0.5/(_intpower[ires]+1.))*MeV;
}
else if(_jactype[ires]==2) {
mass = _intmass[ires];
}
else {
throw DecayPhaseSpaceError() << "Unknown type of Jacobian in "
<< "DecayPhaseSpaceChannel::generateMass"
<< Exception::eventerror;
}
if(mass<lower+1e-10*(lower+upper)) mass=lower+1e-10*(lower+upper);
else if(mass>upper-1e-10*(lower+upper)) mass=upper-1e-10*(lower+upper);
return mass;
}
void DecayPhaseSpaceChannel::twoBodyDecay(const Lorentz5Momentum & p,
const Energy m1, const Energy m2,
Lorentz5Momentum & p1,
Lorentz5Momentum & p2 ) {
static const double eps=1e-6;
double ctheta,phi;
Kinematics::generateAngles(ctheta,phi);
Axis unitDir1=Kinematics::unitDirection(ctheta,phi);
Momentum3 pstarVector;
Energy min=p.mass();
if ( min >= m1 + m2 && m1 >= ZERO && m2 >= ZERO ) {
pstarVector = unitDir1 * Kinematics::pstarTwoBodyDecay(min,m1,m2);
}
else if( m1 >= ZERO && m2 >= ZERO && (m1+m2-min)/(min+m1+m2)<eps) {
pstarVector = Momentum3();
}
else {
throw DecayPhaseSpaceError() << "Two body decay cannot proceed "
<< "p = " << p / GeV
<< " p.m() = " << min / GeV
<< " -> " << m1/GeV
<< ' ' << m2/GeV << Exception::eventerror;
}
p1 = Lorentz5Momentum(m1, pstarVector);
p2 = Lorentz5Momentum(m2,-pstarVector);
// boost from CM to LAB
Boost bv = p.vect() * (1./p.t());
p1.boost( bv );
p2.boost( bv );
}
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