Page Menu
Home
HEPForge
Search
Configure Global Search
Log In
Files
F8309556
No One
Temporary
Actions
View File
Edit File
Delete File
View Transforms
Subscribe
Mute Notifications
Award Token
Flag For Later
Size
18 KB
Subscribers
None
View Options
diff --git a/Hadronization/LightClusterDecayer.cc b/Hadronization/LightClusterDecayer.cc
--- a/Hadronization/LightClusterDecayer.cc
+++ b/Hadronization/LightClusterDecayer.cc
@@ -1,409 +1,415 @@
// -*- C++ -*-
//
// LightClusterDecayer.cc 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, non-templated member
// functions of the LightClusterDecayer class.
//
#include "LightClusterDecayer.h"
#include <ThePEG/Interface/ClassDocumentation.h>
#include <ThePEG/Interface/Parameter.h>
#include <ThePEG/Interface/Reference.h>
#include <ThePEG/Interface/Switch.h>
#include <ThePEG/Persistency/PersistentOStream.h>
#include <ThePEG/Persistency/PersistentIStream.h>
#include <ThePEG/PDT/EnumParticles.h>
#include <ThePEG/Repository/EventGenerator.h>
#include "Cluster.h"
#include "Herwig/Utilities/Kinematics.h"
#include <ThePEG/Utilities/DescribeClass.h>
using namespace Herwig;
DescribeClass<LightClusterDecayer,Interfaced>
describeLightClusterDecayer("Herwig::LightClusterDecayer","Herwig.so");
IBPtr LightClusterDecayer::clone() const {
return new_ptr(*this);
}
IBPtr LightClusterDecayer::fullclone() const {
return new_ptr(*this);
}
void LightClusterDecayer::persistentOutput(PersistentOStream & os) const {
os << _hadronSpectrum;
}
void LightClusterDecayer::persistentInput(PersistentIStream & is, int) {
is >> _hadronSpectrum;
}
void LightClusterDecayer::Init() {
static ClassDocumentation<LightClusterDecayer> documentation
("There is the class responsible for the one-hadron decay of light clusters");
static Reference<LightClusterDecayer,HadronSpectrum>
interfaceHadronSpectrum("HadronSpectrum",
"A reference to the HadronSpectrum object",
&Herwig::LightClusterDecayer::_hadronSpectrum,
false, false, true, false);
}
bool LightClusterDecayer::decay(ClusterVector & clusters, tPVector & finalhadrons) {
// Loop over all clusters, and for those that were not heavy enough
// to undergo to fission, check if they are below the threshold
// for normal two-hadron decays. If this is the case, then the cluster
// should be decayed into a single hadron: this can happen only if
// it is possible to reshuffle momenta between the cluster and
// another one; in the rare occasions in which such exchange of momenta
// is not possible (because all of the clusters are too light) then
// the event is skipped.
// Notice that, differently from what happens in Fortran Herwig,
// light (that is below the threshold for the production of the lightest
// pair of hadrons with the proper flavours) fission products, produced
// by the fission of heavy clusters in class ClusterFissioner
// have been already "decayed" into single hadron (the lightest one
// with proper flavour) by the same latter class, without requiring
// any reshuffling. Therefore the light clusters that are treated in
// this LightClusterDecayer class are produced directly
// (originally) by the class ClusterFinder.
// To preserve all of the information, the cluster partner with which
// the light cluster (that decays into a single hadron) exchanges
// momentum in the reshuffling procedure is redefined and inserted
// in the vector vecNewRedefinedCluPtr. Only at the end, when all
// light clusters have been examined, the elements this vector will be
// copied in collecCluPtr (the reason is that it is not allowed to
// modify a STL container while iterating over it. At the same time,
// this ensures that a cluster can be redefined only once, which seems
// sensible although not strictly necessary).
// Notice that the cluster reshuffling partner is normally redefined
// and inserted in the vector vecNewRedefinedCluPtr, but not always:
// in the case it is also light, then it is also decayed immediately
// into a single hadron, without redefining it (the reason being that,
// otherwise, the would-be redefined cluster could have undefined
// components).
vector<tClusterPtr> redefinedClusters;
for (ClusterVector::const_iterator it = clusters.begin();
it != clusters.end(); ++it) {
// Skip the clusters that are not available or that are
// heavy, intermediate, clusters that have undergone to fission,
if ( ! (*it)->isAvailable() || ! (*it)->isReadyToDecay() ){
continue;
}
// We need to require (at least at the moment, maybe in the future we
// could change it) that the cluster has exactly two components,
// because otherwise we don't know how to deal with the kinematics.
// If this is not the case, then send a warning because it is not suppose
// to happen, and then do nothing with (ignore) such cluster.
if ( (*it)->numComponents() != 2 ) {
generator()->logWarning( Exception("LightClusterDecayer::decay "
"***Still cluster with not exactly"
" 2 components*** ",
Exception::warning) );
continue;
}
if ( DiquarkMatcher::Check((*it)->particle(0)->dataPtr()->id()) && DiquarkMatcher::Check((*it)->particle(1)->dataPtr()->id())) {
// TODO We should never get Diquark Clusters in the LightClusterDecayer
// throw Exception() << "LightClusterDecayer::decay\n"
// "*** Diquark Cluster in LightClusterDecayer ***\n"
// "Cluster = ( "<< (*it)->particle(0)->dataPtr()->id()<<", " << (*it)->particle(1)->dataPtr()->id()<<" )\nMC = " << (*it)->mass()/GeV << " GeV MLHP = "
// << _hadronSpectrum->massLightestHadronPair((*it)->particle(0)->dataPtr(),(*it)->particle(1)->dataPtr())/GeV <<" GeV"
// << Exception::runerror;
continue;
}
// select the hadron for single hadron decay
tcPDPtr hadron = _hadronSpectrum->chooseSingleHadron((*it)->particle(0)->dataPtr(),
(*it)->particle(1)->dataPtr(),
(**it).mass());
// if not single decay continue
if(!hadron){
continue;
}
// We assume that the candidate reshuffling cluster partner,
// with whom the light cluster can exchange momenta,
// is chosen as the closest in space-time between the available
// clusters. Notice that an alternative, sensible approach
// could be to consider instead the "closeness" in the colour
// structure...
// Notice that nor a light cluster (which decays into a single hadron)
// neither its cluster reshuffling partner (which either has a
// redefined cluster or also decays into a single hadron) can be
// a reshuffling partner of another light cluster.
// This because we are requiring that the considered candidate cluster
// reshuffling partner has the status "isAvailable && isReadyToDecay" true;
// furthermore, the new redefined clusters are not added to the collection
// of cluster before the end of the entire reshuffling procedure, avoiding
// in this way that the redefined cluster of a cluster reshuffling partner
// is used again later. Needless to say, this is just an assumption,
// although reasonable, but nothing more than that!
// Build a multimap of available reshuffling cluster partners,
// with key given by the module of the invariant space-time distance
// w.r.t. the light cluster, so that this new collection is automatically
// ordered in increasing distance values.
// We use a multimap, rather than a map, just for precaution against not properly
// defined cluster positions which could produce all identical (null) distances.
multimap<Length,tClusterPtr> candidates;
for ( ClusterVector::iterator jt = clusters.begin();
jt != clusters.end(); ++jt ) {
if ( (*jt)->numComponents() != 2 )
continue;
// if (DiquarkMatcher::Check(*(*jt)->particle(0)->dataPtr())
// && DiquarkMatcher::Check(*(*jt)->particle(1)->dataPtr()))
// continue;
// if ( DiquarkMatcher::Check(*(*jt)->particle(0)->dataPtr())
// && DiquarkMatcher::Check(*(*jt)->particle(1)->dataPtr()))
// continue;
if ((*jt)->isAvailable() && (*jt)->isReadyToDecay() && jt != it) {
Length distance = abs (((*it)->vertex() - (*jt)->vertex()).m());
candidates.insert(pair<Length,tClusterPtr>(distance,*jt));
}
}
// Loop sequentially the multimap.
multimap<Length,tClusterPtr>::const_iterator mmapIt = candidates.begin();
bool found = false;
while (!found && mmapIt != candidates.end()) {
found = reshuffling(hadron, *it, (*mmapIt).second, redefinedClusters, finalhadrons);
if (!found) ++mmapIt;
}
if (!found) return partonicReshuffle(hadron,*it,finalhadrons);
} // end loop over collecCluPtr
// Add to collecCluPtr all of the redefined new clusters (indeed the
// pointers to them are added) contained in vecNewRedefinedCluPtr.
for (tClusterVector::const_iterator it = redefinedClusters.begin();
it != redefinedClusters.end(); ++it) {
clusters.push_back(*it);
}
return true;
}
bool LightClusterDecayer::reshuffling(const tcPDPtr pdata1,
tClusterPtr cluPtr1,
tClusterPtr cluPtr2,
tClusterVector & redefinedClusters,
tPVector & finalhadrons)
{
// don't reshuffle with beam clusters
if(cluPtr2->isBeamCluster()) return false;
// This method does the reshuffling of momenta between the cluster "1",
// that must decay into a single hadron (with id equal to idhad1), and
// the candidate cluster "2". It returns true if the reshuffling succeed,
// false otherwise.
PPtr ptrhad1 = pdata1->produceParticle();
if ( ! ptrhad1 ) {
generator()->logWarning( Exception("LightClusterDecayer::reshuffling"
"***Cannot create a particle with specified id***",
Exception::warning) );
return false;
}
Energy mhad1 = ptrhad1->mass();
// Let's call "3" and "4" the two constituents of the second cluster
tPPtr part3 = cluPtr2->particle(0);
tPPtr part4 = cluPtr2->particle(1);
// Check if the system of the two clusters can kinematically be replaced by
// an hadron of mass mhad1 (which is the lightest single hadron with the
// same flavour numbers as the first cluster) and the second cluster.
// If not, then try to replace the second cluster with the lightest hadron
// with the same flavour numbers; if it still fails, then give up!
Lorentz5Momentum pSystem = cluPtr1->momentum() + cluPtr2->momentum();
pSystem.rescaleMass(); // set the mass as the invariant of the quadri-vector
Energy mSystem = pSystem.mass();
Energy mclu2 = cluPtr2->mass();
bool singleHadron = false;
bool isDiquarkCluster = DiquarkMatcher::Check(part3->dataPtr()->id()) && DiquarkMatcher::Check(part4->dataPtr()->id());
Energy mLHP2 = _hadronSpectrum->massLightestHadronPair(part3->dataPtr(),part4->dataPtr());
// avoid calling massLightestHadron for Diquark clusters and only allow kinematic reshuffling
// for diquark clusters (no singleHadron)
Energy mLH2 = isDiquarkCluster ? mSystem:_hadronSpectrum->massLightestHadron(part3->dataPtr(),part4->dataPtr());
if(mSystem > mhad1 + mclu2 && mclu2 > mLHP2) { singleHadron = false; }
else if(mSystem > mhad1 + mLH2) { singleHadron = true; mclu2 = mLH2; }
else return false;
// Let's call from now on "Sys" the system of the two clusters, and
// had1 (of mass mhad1) the lightest hadron in which the first
// cluster decays, and clu2 (of mass mclu2) either the second
// cluster or the lightest hadron in which it decays (depending
// which one is kinematically allowed, see above).
// The idea behind the reshuffling is to replace the system of the
// two clusters by the system of the hadron had1 and (cluster or hadron) clu2,
// but leaving the overall system unchanged. Furthermore, the motion
// of had1 and clu2 in the Sys frame is assumed to be parallel to, respectively,
// those of the original cluster1 and cluster2 in the same Sys frame.
// Calculate the unit three-vector, in the frame "Sys" along which the
// two initial clusters move.
Lorentz5Momentum u( cluPtr1->momentum() );
u.boost( - pSystem.boostVector() ); // boost from LAB to Sys
// Calculate the momenta of had1 and clu2 in the Sys frame first,
// and then boost back in the LAB frame.
Lorentz5Momentum phad1, pclu2;
if (pSystem.m() < mhad1 + mclu2 ) {
throw Exception() << "Impossible Kinematics in LightClusterDecayer::reshuffling()"
<< Exception::eventerror;
}
-
+ if (!(u.vect().mag2() > ZERO) ) {
+ generator()->logWarning( Exception("Impossible Kinematics in LightClusterDecayer::reshuffling()\n"
+ "Cluster System in Rest frame has |p3| = 0 GeV",
+ Exception::warning) );
+ return false;
+ }
+
Kinematics::twoBodyDecay(pSystem, mhad1, mclu2, u.vect().unit(), phad1, pclu2);
ptrhad1->set5Momentum( phad1 ); // set momentum of first hadron.
ptrhad1->setVertex(cluPtr1->vertex()); // set hadron vertex position to the
// parent cluster position.
cluPtr1->addChild(ptrhad1);
finalhadrons.push_back(ptrhad1);
cluPtr1->flagAsReshuffled();
cluPtr2->flagAsReshuffled();
if(singleHadron) {
// In the case that also the cluster reshuffling partner is light
// it is decayed into a single hadron, *without* creating the
// redefined cluster (this choice is justified in order to avoid
// clusters that could have undefined components).
PPtr ptrhad2 = _hadronSpectrum->lightestHadron(part3->dataPtr(),part4->dataPtr())
->produceParticle();
ptrhad2->set5Momentum( pclu2 );
ptrhad2->setVertex( cluPtr2->vertex() ); // set hadron vertex position to the
// parent cluster position.
cluPtr2->addChild(ptrhad2);
finalhadrons.push_back(ptrhad2);
} else {
// Create the new cluster which is the redefinitions of the cluster
// partner (cluster "2") used in the reshuffling procedure of the
// light cluster (cluster "1").
// The rationale of this is to preserve completely all of the information.
ClusterPtr cluPtr2new = ClusterPtr();
if(part3 && part4) cluPtr2new = new_ptr(Cluster(part3,part4));
cluPtr2new->set5Momentum( pclu2 );
cluPtr2new->setVertex( cluPtr2->vertex() );
cluPtr2->addChild( cluPtr2new );
redefinedClusters.push_back( cluPtr2new );
// Set consistently the momenta of the two components of the second cluster
// after the reshuffling. To do that we first calculate the momenta of the
// constituents in the initial cluster rest frame; then we boost them back
// in the lab but using this time the new cluster rest frame. Finally we store
// these information in the new cluster. Notice that we do *not* set
// consistently also the momenta of the (eventual) particles pointed by the
// two components: that's because we do not need to do so, being the momentum
// an explicit private member of the class Component (which is set equal
// to the momentum of the eventual particle pointed only in the constructor,
// but then later should not necessary be the same), and furthermore it allows
// us not to loose any information, in the sense that we can always, later on,
// to find the original momenta of the two components before the reshuffling.
Lorentz5Momentum p3 = part3->momentum(); //p3new->momentum();
p3.boost( - (cluPtr2->momentum()).boostVector() ); // from LAB to clu2 (old) frame
p3.boost( pclu2.boostVector() ); // from clu2 (new) to LAB frame
Lorentz5Momentum p4 = part4->momentum(); //p4new->momentum();
p4.boost( - (cluPtr2->momentum()).boostVector() ); // from LAB to clu2 (old) frame
p4.boost( pclu2.boostVector() ); // from clu2 (new) to LAB frame
cluPtr2new->particle(0)->set5Momentum(p3);
cluPtr2new->particle(1)->set5Momentum(p4);
} // end of if (singleHadron)
return true;
}
bool LightClusterDecayer::partonicReshuffle(const tcPDPtr had,
const PPtr cluster,
tPVector & finalhadrons) {
tPPtr meson(cluster);
if(!meson->parents().empty()) meson=meson->parents()[0];
if(!meson->parents().empty()) meson=meson->parents()[0];
// check b/c hadron decay
int ptype(abs(meson->id())%10000);
bool heavy = (ptype/1000 == 5 || ptype/1000 ==4 );
heavy |= (ptype/100 == 5 || ptype/100 ==4 );
heavy |= (ptype/10 == 5 || ptype/10 ==4 );
if(!heavy) return false;
// find the leptons
tPVector leptons;
for(unsigned int ix=0;ix<meson->children().size();++ix) {
if(!(meson->children()[ix]->dataPtr()->coloured())) {
leptons.push_back(meson->children()[ix]);
}
}
if(leptons.size()==1) {
tPPtr w=leptons[0];
leptons.pop_back();
for(unsigned int ix=0;ix<w->children().size();++ix) {
if(!w->children()[ix]->dataPtr()->coloured()) {
leptons.push_back(w->children()[ix]);
}
}
}
if(leptons.size()!=2) return false;
// get momentum of leptonic system and the its minimum possible mass
Energy mmin(ZERO);
Lorentz5Momentum pw;
for(unsigned int ix=0;ix<leptons.size();++ix) {
pw+=leptons[ix]->momentum();
mmin+=leptons[ix]->mass();
}
pw.rescaleMass();
// check we can do the reshuffling
PPtr ptrhad = had->produceParticle();
// total momentum fo the system
Lorentz5Momentum pSystem = pw + cluster->momentum();
pSystem.rescaleMass();
// normal case get additional energy by rescaling momentum in rest frame of
// system
if(pSystem.mass()>ptrhad->mass()+pw.mass()&&pw.mass()>mmin) {
// Calculate the unit three-vector, in the frame "Sys" along which the
// two initial clusters move.
Lorentz5Momentum u(cluster->momentum());
u.boost( - pSystem.boostVector() );
// Calculate the momenta of had1 and clu2 in the Sys frame first,
// and then boost back in the LAB frame.
Lorentz5Momentum phad1, pclu2;
Kinematics::twoBodyDecay(pSystem, ptrhad->mass(), pw.mass(),
u.vect().unit(), phad1, pclu2);
// set momentum of first hadron.
ptrhad->set5Momentum( phad1 );
// set hadron vertex position to the parent cluster position.
ptrhad->setLabVertex(cluster->vertex());
// add hadron
cluster->addChild(ptrhad);
finalhadrons.push_back(ptrhad);
// reshuffle the leptons
// boost the leptons to the rest frame of the system
Boost boost1(-pw.boostVector());
Boost boost2( pclu2.boostVector());
for(unsigned int ix=0;ix<leptons.size();++ix) {
leptons[ix]->deepBoost(boost1);
leptons[ix]->deepBoost(boost2);
}
return true;
}
else {
return false;
}
}
File Metadata
Details
Attached
Mime Type
text/x-diff
Expires
Sat, Dec 21, 3:44 PM (1 d, 7 h)
Storage Engine
blob
Storage Format
Raw Data
Storage Handle
4023332
Default Alt Text
(18 KB)
Attached To
rHERWIGHG herwighg
Event Timeline
Log In to Comment