ShowerHandler.cc
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ShowerHandler.cc
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	// -- C++ --
	//
	// ShowerHandler.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 ShowerHandler class.
	//

	#include "ShowerHandler.h"
	#include "ThePEG/Interface/ClassDocumentation.h"
	#include "ThePEG/Interface/Reference.h"
	#include "ThePEG/Interface/Parameter.h"
	#include "ThePEG/Interface/ParVector.h"
	#include "ThePEG/Interface/Switch.h"
	#include "ThePEG/Interface/Command.h"
	#include "ThePEG/PDF/PartonExtractor.h"
	#include "ThePEG/PDF/PartonBinInstance.h"
	#include "Herwig/PDT/StandardMatchers.h"
	#include "ThePEG/Cuts/Cuts.h"
	#include "ThePEG/Handlers/StandardXComb.h"
	#include "ThePEG/Utilities/Throw.h"
	#include "ThePEG/Utilities/StringUtils.h"
	#include "ThePEG/Persistency/PersistentOStream.h"
	#include "ThePEG/Persistency/PersistentIStream.h"
	#include "ThePEG/Repository/EventGenerator.h"
	#include "Herwig/Utilities/EnumParticles.h"
	#include "Herwig/PDF/MPIPDF.h"
	#include "Herwig/PDF/MinBiasPDF.h"
	#include "ThePEG/Handlers/EventHandler.h"
	#include "Herwig/Shower/QTilde/Base/ShowerTree.h"
	#include "Herwig/PDF/HwRemDecayer.h"
	#include <cassert>
	#include "ThePEG/Utilities/DescribeClass.h"

	using namespace Herwig;

	DescribeClass<ShowerHandler,CascadeHandler>
	describeShowerHandler ("Herwig::ShowerHandler","HwShower.so");

	ShowerHandler::~ShowerHandler() {}

	tShowerHandlerPtr ShowerHandler::currentHandler_ = tShowerHandlerPtr();

	void ShowerHandler::doinit() {
	CascadeHandler::doinit();
	// copy particles to decay before showering from input vector to the
	// set used in the simulation
	if ( particlesDecayInShower_.empty() )
	particlesDecayInShower_.insert(inputparticlesDecayInShower_.begin(),
	inputparticlesDecayInShower_.end());
	ShowerTree::_vmin2 = vMin_;
	ShowerTree::_spaceTime = includeSpaceTime_;
	}

	IBPtr ShowerHandler::clone() const {
	return new_ptr(*this);
	}

	IBPtr ShowerHandler::fullclone() const {
	return new_ptr(*this);
	}

	ShowerHandler::ShowerHandler() :
	maxtry_(10),maxtryMPI_(10),maxtryDP_(10),maxtryDecay_(100),
	factorizationScaleFactor_(1.0),
	renormalizationScaleFactor_(1.0),
	hardScaleFactor_(1.0),
	restrictPhasespace_(true), maxPtIsMuF_(false),
	pdfFreezingScale_(2.5*GeV),
	doFSR_(true), doISR_(true),
	splitHardProcess_(true),
	includeSpaceTime_(false), vMin_(0.1*GeV2),
	reweight_(1.0) {
	inputparticlesDecayInShower_.push_back( 6 ); // top
	inputparticlesDecayInShower_.push_back( 23 ); // Z0
	inputparticlesDecayInShower_.push_back( 24 ); // W+/-
	inputparticlesDecayInShower_.push_back( 25 ); // h0
	}

	void ShowerHandler::doinitrun(){
	CascadeHandler::doinitrun();
	//can't use isMPIOn here, because the EventHandler is not set at that stage
	if(MPIHandler_) {
	MPIHandler_->initialize();
	if(MPIHandler_->softInt())
	remDec_->initSoftInteractions(MPIHandler_->Ptmin(), MPIHandler_->beta());
	}
	ShowerTree::_vmin2 = vMin_;
	ShowerTree::_spaceTime = includeSpaceTime_;
	}

	void ShowerHandler::dofinish(){
	CascadeHandler::dofinish();
	if(MPIHandler_) MPIHandler_->finalize();
	}

	void ShowerHandler::persistentOutput(PersistentOStream & os) const {
	os << remDec_ << ounit(pdfFreezingScale_,GeV) << maxtry_
	<< maxtryMPI_ << maxtryDP_ << inputparticlesDecayInShower_
	<< particlesDecayInShower_ << MPIHandler_ << PDFA_ << PDFB_
	<< PDFARemnant_ << PDFBRemnant_
	<< includeSpaceTime_ << ounit(vMin_,GeV2)
	<< factorizationScaleFactor_ << renormalizationScaleFactor_
	<< hardScaleFactor_
	<< restrictPhasespace_ << maxPtIsMuF_ << hardScaleProfile_
	<< showerVariations_ << doFSR_ << doISR_ << splitHardProcess_;
	}

	void ShowerHandler::persistentInput(PersistentIStream & is, int) {
	is >> remDec_ >> iunit(pdfFreezingScale_,GeV) >> maxtry_
	>> maxtryMPI_ >> maxtryDP_ >> inputparticlesDecayInShower_
	>> particlesDecayInShower_ >> MPIHandler_ >> PDFA_ >> PDFB_
	>> PDFARemnant_ >> PDFBRemnant_
	>> includeSpaceTime_ >> iunit(vMin_,GeV2)
	>> factorizationScaleFactor_ >> renormalizationScaleFactor_
	>> hardScaleFactor_
	>> restrictPhasespace_ >> maxPtIsMuF_ >> hardScaleProfile_
	>> showerVariations_ >> doFSR_ >> doISR_ >> splitHardProcess_;
	}

	void ShowerHandler::Init() {

	static ClassDocumentation<ShowerHandler> documentation
	("Main driver class for the showering.");

	static Reference<ShowerHandler,HwRemDecayer>
	interfaceRemDecayer("RemDecayer",
	"A reference to the Remnant Decayer object",
	&Herwig::ShowerHandler::remDec_,
	false, false, true, false);

	static Parameter<ShowerHandler,Energy> interfacePDFFreezingScale
	("PDFFreezingScale",
	"The PDF freezing scale",
	&ShowerHandler::pdfFreezingScale_, GeV, 2.5GeV, 2.0GeV, 10.0*GeV,
	false, false, Interface::limited);

	static Parameter<ShowerHandler,unsigned int> interfaceMaxTry
	("MaxTry",
	"The maximum number of attempts for the main showering loop",
	&ShowerHandler::maxtry_, 10, 1, 100,
	false, false, Interface::limited);

	static Parameter<ShowerHandler,unsigned int> interfaceMaxTryMPI
	("MaxTryMPI",
	"The maximum number of regeneration attempts for an additional scattering",
	&ShowerHandler::maxtryMPI_, 10, 0, 100,
	false, false, Interface::limited);

	static Parameter<ShowerHandler,unsigned int> interfaceMaxTryDP
	("MaxTryDP",
	"The maximum number of regeneration attempts for an additional hard scattering",
	&ShowerHandler::maxtryDP_, 10, 0, 100,
	false, false, Interface::limited);

	static ParVector<ShowerHandler,long> interfaceDecayInShower
	("DecayInShower",
	"PDG codes of the particles to be decayed in the shower",
	&ShowerHandler::inputparticlesDecayInShower_, -1, 0l, -10000000l, 10000000l,
	false, false, Interface::limited);

	static Reference<ShowerHandler,UEBase> interfaceMPIHandler
	("MPIHandler",
	"The object that administers all additional scatterings.",
	&ShowerHandler::MPIHandler_, false, false, true, true);

	static Reference<ShowerHandler,PDFBase> interfacePDFA
	("PDFA",
	"The PDF for beam particle A. Overrides the particle's own PDF setting."
	"By default used for both the shower and forced splitting in the remnant",
	&ShowerHandler::PDFA_, false, false, true, true, false);

	static Reference<ShowerHandler,PDFBase> interfacePDFB
	("PDFB",
	"The PDF for beam particle B. Overrides the particle's own PDF setting."
	"By default used for both the shower and forced splitting in the remnant",
	&ShowerHandler::PDFB_, false, false, true, true, false);

	static Reference<ShowerHandler,PDFBase> interfacePDFARemnant
	("PDFARemnant",
	"The PDF for beam particle A used to generate forced splittings of the remnant."
	" This overrides both the particle's own PDF setting and the value set by PDFA if used.",
	&ShowerHandler::PDFARemnant_, false, false, true, true, false);

	static Reference<ShowerHandler,PDFBase> interfacePDFBRemnant
	("PDFBRemnant",
	"The PDF for beam particle B used to generate forced splittings of the remnant."
	" This overrides both the particle's own PDF setting and the value set by PDFB if used.",
	&ShowerHandler::PDFBRemnant_, false, false, true, true, false);


	static Switch<ShowerHandler,bool> interfaceIncludeSpaceTime
	("IncludeSpaceTime",
	"Whether to include the model for the calculation of space-time distances",
	&ShowerHandler::includeSpaceTime_, false, false, false);
	static SwitchOption interfaceIncludeSpaceTimeYes
	(interfaceIncludeSpaceTime,
	"Yes",
	"Include the model",
	true);
	static SwitchOption interfaceIncludeSpaceTimeNo
	(interfaceIncludeSpaceTime,
	"No",
	"Only include the displacement from the particle-s lifetime for decaying particles",
	false);

	static Parameter<ShowerHandler,Energy2> interfaceMinimumVirtuality
	("MinimumVirtuality",
	"The minimum virtuality for the space-time model",
	&ShowerHandler::vMin_, GeV2, 0.1GeV2, 0.0GeV2, 1000.0*GeV2,
	false, false, Interface::limited);

	static Parameter<ShowerHandler,double> interfaceFactorizationScaleFactor
	("FactorizationScaleFactor",
	"The factorization scale factor.",
	&ShowerHandler::factorizationScaleFactor_, 1.0, 0.0, 0,
	false, false, Interface::lowerlim);

	static Parameter<ShowerHandler,double> interfaceRenormalizationScaleFactor
	("RenormalizationScaleFactor",
	"The renormalization scale factor.",
	&ShowerHandler::renormalizationScaleFactor_, 1.0, 0.0, 0,
	false, false, Interface::lowerlim);

	static Parameter<ShowerHandler,double> interfaceHardScaleFactor
	("HardScaleFactor",
	"The hard scale factor.",
	&ShowerHandler::hardScaleFactor_, 1.0, 0.0, 0,
	false, false, Interface::lowerlim);

	static Reference<ShowerHandler,HardScaleProfile> interfaceHardScaleProfile
	("HardScaleProfile",
	"The hard scale profile to use.",
	&ShowerHandler::hardScaleProfile_, false, false, true, true, false);

	static Switch<ShowerHandler,bool> interfaceMaxPtIsMuF
	("MaxPtIsMuF",
	"",
	&ShowerHandler::maxPtIsMuF_, false, false, false);
	static SwitchOption interfaceMaxPtIsMuFYes
	(interfaceMaxPtIsMuF,
	"Yes",
	"",
	true);
	static SwitchOption interfaceMaxPtIsMuFNo
	(interfaceMaxPtIsMuF,
	"No",
	"",
	false);

	static Switch<ShowerHandler,bool> interfaceRestrictPhasespace
	("RestrictPhasespace",
	"Switch on or off phasespace restrictions",
	&ShowerHandler::restrictPhasespace_, true, false, false);
	static SwitchOption interfaceRestrictPhasespaceOn
	(interfaceRestrictPhasespace,
	"On",
	"Perform phasespace restrictions",
	true);
	static SwitchOption interfaceRestrictPhasespaceOff
	(interfaceRestrictPhasespace,
	"Off",
	"Do not perform phasespace restrictions",
	false);

	static Command<ShowerHandler> interfaceAddVariation
	("AddVariation",
	"Add a shower variation.",
	&ShowerHandler::doAddVariation, false);

	static Switch<ShowerHandler,bool> interfaceDoFSR
	("DoFSR",
	"Switch on or off final state radiation.",
	&ShowerHandler::doFSR_, true, false, false);
	static SwitchOption interfaceDoFSROn
	(interfaceDoFSR,
	"Yes",
	"Switch on final state radiation.",
	true);
	static SwitchOption interfaceDoFSROff
	(interfaceDoFSR,
	"No",
	"Switch off final state radiation.",
	false);

	static Switch<ShowerHandler,bool> interfaceDoISR
	("DoISR",
	"Switch on or off initial state radiation.",
	&ShowerHandler::doISR_, true, false, false);
	static SwitchOption interfaceDoISROn
	(interfaceDoISR,
	"Yes",
	"Switch on initial state radiation.",
	true);
	static SwitchOption interfaceDoISROff
	(interfaceDoISR,
	"No",
	"Switch off initial state radiation.",
	false);

	static Switch<ShowerHandler,bool> interfaceSplitHardProcess
	("SplitHardProcess",
	"Whether or not to try and split the hard process into production and decay processes",
	&ShowerHandler::splitHardProcess_, true, false, false);
	static SwitchOption interfaceSplitHardProcessYes
	(interfaceSplitHardProcess,
	"Yes",
	"Split the hard process",
	true);
	static SwitchOption interfaceSplitHardProcessNo
	(interfaceSplitHardProcess,
	"No",
	"Don't split the hard process",
	false);
	}

	Energy ShowerHandler::hardScale() const {
	assert(false);
	}

	void ShowerHandler::cascade() {
	useMe();
	// Initialise the weights in the event object
	// so that any variations are output regardless of
	// whether showering occurs for the given event
	initializeWeights();
	// get the PDF's from ThePEG (if locally overridden use the local versions)
	tcPDFPtr first = PDFA_ ? tcPDFPtr(PDFA_) : firstPDF().pdf();
	tcPDFPtr second = PDFB_ ? tcPDFPtr(PDFB_) : secondPDF().pdf();
	resetPDFs(make_pair(first,second));
	// set the PDFs for the remnant
	if( ! rempdfs_.first)
	rempdfs_.first = PDFARemnant_ ? PDFPtr(PDFARemnant_) : const_ptr_cast<PDFPtr>(first);
	if( ! rempdfs_.second)
	rempdfs_.second = PDFBRemnant_ ? PDFPtr(PDFBRemnant_) : const_ptr_cast<PDFPtr>(second);
	// get the incoming partons
	tPPair incomingPartons =
	eventHandler()->currentCollision()->primarySubProcess()->incoming();
	// and the parton bins
	PBIPair incomingBins =
	make_pair(lastExtractor()->partonBinInstance(incomingPartons.first),
	lastExtractor()->partonBinInstance(incomingPartons.second));
	// and the incoming hadrons
	tPPair incomingHadrons =
	eventHandler()->currentCollision()->incoming();
	remDec_->setHadronContent(incomingHadrons);
	// check if incoming hadron == incoming parton
	// and get the incoming hadron if exists or parton otherwise
	incoming_ = make_pair(incomingBins.first ?
	incomingBins.first ->particle() : incomingPartons.first,
	incomingBins.second ?
	incomingBins.second->particle() : incomingPartons.second);
	// check the collision is of the beam particles
	// and if not boost collision to the right frame
	// i.e. the hadron-hadron CMF of the collision
	bool btotal(false);
	LorentzRotation rtotal;
	if(incoming_.first != incomingHadrons.first \|\|
	incoming_.second != incomingHadrons.second ) {
	btotal = true;
	boostCollision(false);
	}
	// set the current ShowerHandler
	setCurrentHandler();
	// first shower the hard process
	try {
	SubProPtr sub = eventHandler()->currentCollision()->primarySubProcess();
	incomingPartons = cascade(sub,lastXCombPtr());
	}
	catch(ShowerTriesVeto &veto){
	throw Exception() << "Failed to generate the shower after "
	<< veto.tries
	<< " attempts in ShowerHandler::cascade()"
	<< Exception::eventerror;
	}
	if(showerHardProcessVeto()) throw Veto();
	// if a non-hadron collision return (both incoming non-hadronic)
	if( ( !incomingBins.first\|\|
	!isResolvedHadron(incomingBins.first ->particle()))&&
	( !incomingBins.second\|\|
	!isResolvedHadron(incomingBins.second->particle()))) {
	// boost back to lab if needed
	if(btotal) boostCollision(true);
	// perform the reweighting for the hard process shower
	combineWeights();
	// unset the current ShowerHandler
	unSetCurrentHandler();
	return;
	}
	// get the remnants for hadronic collision
	pair<tRemPPtr,tRemPPtr> remnants(getRemnants(incomingBins));
	// set the starting scale of the forced splitting to the PDF freezing scale
	remnantDecayer()->initialize(remnants, incoming_, *currentStep(), pdfFreezingScale());
	// do the first forcedSplitting
	try {
	remnantDecayer()->doSplit(incomingPartons, make_pair(rempdfs_.first,rempdfs_.second), true);
	}
	catch (ExtraScatterVeto) {
	throw Exception() << "Remnant extraction failed in "
	<< "ShowerHandler::cascade() from primary interaction"
	<< Exception::eventerror;
	}
	// perform the reweighting for the hard process shower
	combineWeights();
	// if no MPI return
	if( !isMPIOn() ) {
	remDec_->finalize();
	// boost back to lab if needed
	if(btotal) boostCollision(true);
	// unset the current ShowerHandler
	unSetCurrentHandler();
	return;
	}
	// generate the multiple scatters use modified pdf's now:
	setMPIPDFs();
	// additional "hard" processes
	unsigned int tries(0);
	// This is the loop over additional hard scatters (most of the time
	// only one, but who knows...)
	for(unsigned int i=1; i <= getMPIHandler()->additionalHardProcs(); i++){
	//counter for regeneration
	unsigned int multSecond = 0;
	// generate the additional scatters
	while( multSecond < getMPIHandler()->multiplicity(i) ) {
	// generate the hard scatter
	tStdXCombPtr lastXC = getMPIHandler()->generate(i);
	SubProPtr sub = lastXC->construct();
	// add to the Step
	newStep()->addSubProcess(sub);
	// increment the counters
	tries++;
	multSecond++;
	if(tries == maxtryDP_)
	throw Exception() << "Failed to establish the requested number "
	<< "of additional hard processes. If this error "
	<< "occurs often, your selection of additional "
	<< "scatter is probably unphysical"
	<< Exception::eventerror;
	// Generate the shower. If not possible veto the event
	try {
	incomingPartons = cascade(sub,lastXC);
	}
	catch(ShowerTriesVeto &veto){
	throw Exception() << "Failed to generate the shower of "
	<< "a secondary hard process after "
	<< veto.tries
	<< " attempts in Evolver::showerHardProcess()"
	<< Exception::eventerror;
	}
	try {
	// do the forcedSplitting
	remnantDecayer()->doSplit(incomingPartons, make_pair(remmpipdfs_.first,remmpipdfs_.second), false);
	}
	catch(ExtraScatterVeto){
	//remove all particles associated with the subprocess
	newStep()->removeParticle(incomingPartons.first);
	newStep()->removeParticle(incomingPartons.second);
	//remove the subprocess from the list
	newStep()->removeSubProcess(sub);
	//regenerate the scattering
	multSecond--;
	continue;
	}
	// connect with the remnants but don't set Remnant colour,
	// because that causes problems due to the multiple colour lines.
	if ( !remnants.first ->extract(incomingPartons.first , false) \|\|
	!remnants.second->extract(incomingPartons.second, false) )
	throw Exception() << "Remnant extraction failed in "
	<< "ShowerHandler::cascade() for additional scatter"
	<< Exception::runerror;
	}
	// perform the reweighting for the additional hard scatter shower
	combineWeights();
	}
	// the underlying event processes
	unsigned int ptveto(1), veto(0);
	unsigned int max(getMPIHandler()->multiplicity());
	for(unsigned int i=0; i<max; i++) {
	// check how often this scattering has been regenerated
	if(veto > maxtryMPI_) break;
	//generate PSpoint
	tStdXCombPtr lastXC = getMPIHandler()->generate();
	SubProPtr sub = lastXC->construct();
	//If Algorithm=1 additional scatters of the signal type
	// with pt > ptmin have to be vetoed
	//with probability 1/(m+1), where m is the number of occurances in this event
	if( getMPIHandler()->Algorithm() == 1 ){
	//get the pT
	Energy pt = sub->outgoing().front()->momentum().perp();
	if(pt > getMPIHandler()->PtForVeto() && UseRandom::rnd() < 1./(ptveto+1) ){
	ptveto++;
	i--;
	continue;
	}
	}
	// add to the SubProcess to the step
	newStep()->addSubProcess(sub);
	// Run the Shower. If not possible veto the scattering
	try {
	incomingPartons = cascade(sub,lastXC);
	}
	// discard this extra scattering, but try the next one
	catch(ShowerTriesVeto) {
	newStep()->removeSubProcess(sub);
	//regenerate the scattering
	veto++;
	i--;
	continue;
	}
	try{
	//do the forcedSplitting
	remDec_->doSplit(incomingPartons, make_pair(remmpipdfs_.first,remmpipdfs_.second), false);
	}
	catch (ExtraScatterVeto) {
	//remove all particles associated with the subprocess
	newStep()->removeParticle(incomingPartons.first);
	newStep()->removeParticle(incomingPartons.second);
	//remove the subprocess from the list
	newStep()->removeSubProcess(sub);
	//regenerate the scattering
	veto++;
	i--;
	continue;
	}
	//connect with the remnants but don't set Remnant colour,
	//because that causes problems due to the multiple colour lines.
	if ( !remnants.first ->extract(incomingPartons.first , false) \|\|
	!remnants.second->extract(incomingPartons.second, false) )
	throw Exception() << "Remnant extraction failed in "
	<< "ShowerHandler::cascade() for MPI hard scattering"
	<< Exception::runerror;
	//reset veto counter
	veto = 0;
	// perform the reweighting for the MPI process shower
	combineWeights();
	}
	// finalize the remnants
	remDec_->finalize(getMPIHandler()->colourDisrupt(),
	getMPIHandler()->softMultiplicity());
	// boost back to lab if needed
	if(btotal) boostCollision(true);
	// unset the current ShowerHandler
	unSetCurrentHandler();
	getMPIHandler()->clean();
	}

	void ShowerHandler::initializeWeights() {
	if ( !showerVariations().empty() ) {

	tEventPtr event = eventHandler()->currentEvent();

	for ( map<string,ShowerVariation>::const_iterator var =
	showerVariations().begin();
	var != showerVariations().end(); ++var ) {

	// Check that this is behaving as intended
	//map<string,double>::iterator wi = event->optionalWeights().find(var->first);
	//assert(wi == event->optionalWeights().end() );

	event->optionalWeights()[var->first] = 1.0;
	currentWeights_[var->first] = 1.0;
	}
	}
	reweight_ = 1.0;
	}

	void ShowerHandler::resetWeights() {
	for ( map<string,double>::iterator w = currentWeights_.begin();
	w != currentWeights_.end(); ++w ) {
	w->second = 1.0;
	}
	reweight_ = 1.0;
	}

	void ShowerHandler::combineWeights() {
	tEventPtr event = eventHandler()->currentEvent();
	for ( map<string,double>::const_iterator w =
	currentWeights_.begin(); w != currentWeights_.end(); ++w ) {
	map<string,double>::iterator ew = event->optionalWeights().find(w->first);
	if ( ew != event->optionalWeights().end() )
	ew->second *= w->second;
	else {
	assert(false && "Weight name unknown.");
	//event->optionalWeights()[w->first] = w->second;
	}
	}
	if ( reweight_ != 1.0 ) {
	Ptr<StandardEventHandler>::tptr eh =
	dynamic_ptr_cast<Ptr<StandardEventHandler>::tptr>(eventHandler());
	if ( !eh ) {
	throw Exception() << "ShowerHandler::combineWeights() : Cross section reweighting "
	<< "through the shower is currently only available with standard "
	<< "event generators" << Exception::runerror;
	}
	eh->reweight(reweight_);
	}
	}

	string ShowerHandler::doAddVariation(string in) {
	if ( in.empty() )
	return "expecting a name and a variation specification";
	string name = StringUtils::car(in);
	ShowerVariation var;
	string res = var.fromInFile(StringUtils::cdr(in));
	if ( res.empty() ) {
	if ( !var.firstInteraction && !var.secondaryInteractions ) {
	// TODO what about decay showers?
	return "variation does not apply to any shower";
	}
	if ( var.renormalizationScaleFactor == 1.0 &&
	var.factorizationScaleFactor == 1.0 ) {
	return "variation does not vary anything";
	}
	/*
	Repository::clog() << "adding a variation with tag '" << name << "' using\nxir = "
	<< var.renormalizationScaleFactor
	<< " xif = "
	<< var.factorizationScaleFactor
	<< "\napplying to:\n"
	<< "first interaction = " << var.firstInteraction << " "
	<< "secondary interactions = " << var.secondaryInteractions << "\n"
	<< flush;
	*/
	showerVariations()[name] = var;
	}
	return res;
	}

	tPPair ShowerHandler::cascade(tSubProPtr, XCPtr) {
	assert(false);
	}

	ShowerHandler::RemPair
	ShowerHandler::getRemnants(PBIPair incomingBins) {
	RemPair remnants;
	// first beam particle
	if(incomingBins.first&&!incomingBins.first->remnants().empty()) {
	remnants.first =
	dynamic_ptr_cast<tRemPPtr>(incomingBins.first->remnants()[0] );
	if(remnants.first) {
	ParticleVector children=remnants.first->children();
	for(unsigned int ix=0;ix<children.size();++ix) {
	if(children[ix]->dataPtr()==remnants.first->dataPtr())
	remnants.first = dynamic_ptr_cast<RemPPtr>(children[ix]);
	}
	//remove existing colour lines from the remnants
	if(remnants.first->colourLine())
	remnants.first->colourLine()->removeColoured(remnants.first);
	if(remnants.first->antiColourLine())
	remnants.first->antiColourLine()->removeAntiColoured(remnants.first);
	}
	}
	// seconnd beam particle
	if(incomingBins.second&&!incomingBins. second->remnants().empty()) {
	remnants.second =
	dynamic_ptr_cast<tRemPPtr>(incomingBins.second->remnants()[0] );
	if(remnants.second) {
	ParticleVector children=remnants.second->children();
	for(unsigned int ix=0;ix<children.size();++ix) {
	if(children[ix]->dataPtr()==remnants.second->dataPtr())
	remnants.second = dynamic_ptr_cast<RemPPtr>(children[ix]);
	}
	//remove existing colour lines from the remnants
	if(remnants.second->colourLine())
	remnants.second->colourLine()->removeColoured(remnants.second);
	if(remnants.second->antiColourLine())
	remnants.second->antiColourLine()->removeAntiColoured(remnants.second);
	}
	}
	assert(remnants.first \|\| remnants.second);
	return remnants;
	}

	namespace {

	void addChildren(tPPtr in,set<tPPtr> & particles) {
	particles.insert(in);
	for(unsigned int ix=0;ix<in->children().size();++ix)
	addChildren(in->children()[ix],particles);
	}
	}

	void ShowerHandler::boostCollision(bool boost) {
	// calculate boost from lab to rest
	if(!boost) {
	Lorentz5Momentum ptotal=incoming_.first ->momentum()+incoming_.second->momentum();
	boost_ = LorentzRotation(-ptotal.boostVector());
	Axis axis((boost_*incoming_.first ->momentum()).vect().unit());
	if(axis.perp2()>0.) {
	double sinth(sqrt(sqr(axis.x())+sqr(axis.y())));
	boost_.rotate(-acos(axis.z()),Axis(-axis.y()/sinth,axis.x()/sinth,0.));
	}
	}
	// first call performs the boost and second inverse
	// get the particles to be boosted
	set<tPPtr> particles;
	addChildren(incoming_.first,particles);
	addChildren(incoming_.second,particles);
	// apply the boost
	for(set<tPPtr>::const_iterator cit=particles.begin();
	cit!=particles.end();++cit) {
	(*cit)->transform(boost_);
	}
	if(!boost) boost_.invert();
	}

	void ShowerHandler::setMPIPDFs() {

	if ( !mpipdfs_.first ) {
	// first have to check for MinBiasPDF
	tcMinBiasPDFPtr first = dynamic_ptr_cast<tcMinBiasPDFPtr>(firstPDF().pdf());
	if(first)
	mpipdfs_.first = new_ptr(MPIPDF(first->originalPDF()));
	else
	mpipdfs_.first = new_ptr(MPIPDF(firstPDF().pdf()));
	}

	if ( !mpipdfs_.second ) {
	tcMinBiasPDFPtr second = dynamic_ptr_cast<tcMinBiasPDFPtr>(secondPDF().pdf());
	if(second)
	mpipdfs_.second = new_ptr(MPIPDF(second->originalPDF()));
	else
	mpipdfs_.second = new_ptr(MPIPDF(secondPDF().pdf()));
	}

	if( !remmpipdfs_.first ) {
	tcMinBiasPDFPtr first = dynamic_ptr_cast<tcMinBiasPDFPtr>(rempdfs_.first);
	if(first)
	remmpipdfs_.first = new_ptr(MPIPDF(first->originalPDF()));
	else
	remmpipdfs_.first = new_ptr(MPIPDF(rempdfs_.first));
	}

	if( !remmpipdfs_.second ) {
	tcMinBiasPDFPtr second = dynamic_ptr_cast<tcMinBiasPDFPtr>(rempdfs_.second);
	if(second)
	remmpipdfs_.second = new_ptr(MPIPDF(second->originalPDF()));
	else
	remmpipdfs_.second = new_ptr(MPIPDF(rempdfs_.second));
	}
	// reset the PDFs stored in the base class
	resetPDFs(mpipdfs_);

	}

	bool ShowerHandler::isResolvedHadron(tPPtr particle) {
	if(!HadronMatcher::Check(particle->data())) return false;
	for(unsigned int ix=0;ix<particle->children().size();++ix) {
	if(particle->children()[ix]->id()==ParticleID::Remnant) return true;
	}
	return false;
	}

	namespace {

	bool decayProduct(tSubProPtr subProcess,
	tPPtr particle) {
	// must be time-like and not incoming
	if(particle->momentum().m2()<=ZERO\|\|
	particle == subProcess->incoming().first\|\|
	particle == subProcess->incoming().second) return false;
	// if only 1 outgoing and this is it
	if(subProcess->outgoing().size()==1 &&
	subProcess->outgoing()[0]==particle) return true;
	// must not be the s-channel intermediate otherwise
	if(find(subProcess->incoming().first->children().begin(),
	subProcess->incoming().first->children().end(),particle)!=
	subProcess->incoming().first->children().end()&&
	find(subProcess->incoming().second->children().begin(),
	subProcess->incoming().second->children().end(),particle)!=
	subProcess->incoming().second->children().end()&&
	subProcess->incoming().first ->children().size()==1&&
	subProcess->incoming().second->children().size()==1)
	return false;
	// if non-coloured this is enough
	if(!particle->dataPtr()->coloured()) return true;
	// if coloured must be unstable
	if(particle->dataPtr()->stable()) return false;
	// must not have same particle type as a child
	int id = particle->id();
	for(unsigned int ix=0;ix<particle->children().size();++ix)
	if(particle->children()[ix]->id()==id) return false;
	// otherwise its a decaying particle
	return true;
	}

	PPtr findParent(PPtr original, bool & isHard,
	set<PPtr> outgoingset,
	tSubProPtr subProcess) {
	PPtr parent=original;
	isHard \|=(outgoingset.find(original) != outgoingset.end());
	if(!original->parents().empty()) {
	PPtr orig=original->parents()[0];
	if(CurrentGenerator::current().currentEventHandler()->currentStep()->
	find(orig)&&decayProduct(subProcess,orig)) {
	parent=findParent(orig,isHard,outgoingset,subProcess);
	}
	}
	return parent;
	}
	}

	void ShowerHandler::findDecayProducts(PPtr in,PerturbativeProcessPtr hard,
	DecayProcessMap decay) const {
	ParticleVector children=in->children();
	for(ParticleVector::const_iterator it=children.begin(); it!=children.end();++it) {
	// if decayed or should be decayed in shower make the PerturbaitveProcess
	bool radiates = false;
	if(!(**it).children().empty()) {
	// remove d,u,s,c,b quarks and leptons other than on-shell taus
	if( StandardQCDPartonMatcher::Check((**it).id()) \|\|
	( LeptonMatcher::Check((it).id()) && !(abs((it).id())==ParticleID::tauminus &&
	abs((it).mass()-(it).dataPtr()->mass())<MeV))) {
	radiates = true;
	}
	else {
	bool foundParticle(false),foundGauge(false);
	for(unsigned int iy=0;iy<(**it).children().size();++iy) {
	if((it).children()[iy]->id()==(it).id()) {
	foundParticle = true;
	}
	else if((**it).children()[iy]->id()==ParticleID::g \|\|
	(**it).children()[iy]->id()==ParticleID::gamma) {
	foundGauge = true;
	}
	}
	radiates = foundParticle && foundGauge;
	}
	}
	if(radiates) {
	findDecayProducts(*it,hard,decay);
	}
	else if(!(**it).children().empty()\|\|
	(decaysInShower((it).id())&&!(it).dataPtr()->stable())) {
	createDecayProcess(in,hard,decay);
	}
	else {
	hard->outgoing().push_back(make_pair(*it,PerturbativeProcessPtr()));
	}
	}
	}

	void ShowerHandler::splitHardProcess(tPVector tagged, PerturbativeProcessPtr & hard,
	DecayProcessMap & decay) const {
	// temporary storage of the particles
	set<PPtr> hardParticles;
	// tagged particles in a set
	set<PPtr> outgoingset(tagged.begin(),tagged.end());
	bool isHard=false;
	// loop over the tagged particles
	for (tParticleVector::const_iterator taggedP = tagged.begin();
	taggedP != tagged.end(); ++taggedP) {
	// skip remnants
	if(eventHandler()->currentCollision()->isRemnant(*taggedP)) continue;
	// find the parent and whether its a decaying particle
	bool isDecayProd=false;
	// check if hard
	isHard \|=(outgoingset.find(*taggedP) != outgoingset.end());
	if(splitHardProcess_) {
	tPPtr parent = *taggedP;
	// check if from s channel decaying colourless particle
	while(parent&&!parent->parents().empty()&&!isDecayProd) {
	parent = parent->parents()[0];
	if(parent == subProcess_->incoming().first \|\|
	parent == subProcess_->incoming().second ) break;
	isDecayProd = decayProduct(subProcess_,parent);
	}
	if (isDecayProd)
	hardParticles.insert(findParent(parent,isHard,outgoingset,subProcess_));
	}
	if (!isDecayProd)
	hardParticles.insert(*taggedP);
	}
	// there must be something to shower
	if(hardParticles.empty())
	throw Exception() << "No particles to shower in "
	<< "ShowerHandler::splitHardProcess()"
	<< Exception::eventerror;
	// must be a hard process
	if(!isHard)
	throw Exception() << "Starting on decay not yet implemented in "
	<< "ShowerHandler::splitHardProcess()"
	<< Exception::runerror;
	// create the hard process
	hard = new_ptr(PerturbativeProcess());
	// incoming particles
	hard->incoming().push_back(make_pair(subProcess_->incoming().first ,PerturbativeProcessPtr()));
	hard->incoming().push_back(make_pair(subProcess_->incoming().second,PerturbativeProcessPtr()));
	// outgoing particles
	for(set<PPtr>::const_iterator it=hardParticles.begin();it!=hardParticles.end();++it) {
	// if decayed or should be decayed in shower make the tree
	PPtr orig = *it;
	bool radiates = false;
	if(!orig->children().empty()) {
	// remove d,u,s,c,b quarks and leptons other than on-shell taus
	if( StandardQCDPartonMatcher::Check(orig->id()) \|\|
	( LeptonMatcher::Check(orig->id()) &&
	!(abs(orig->id())==ParticleID::tauminus && abs(orig->mass()-orig->dataPtr()->mass())<MeV))) {
	radiates = true;
	}
	else {
	bool foundParticle(false),foundGauge(false);
	for(unsigned int iy=0;iy<orig->children().size();++iy) {
	if(orig->children()[iy]->id()==orig->id()) {
	foundParticle = true;
	}
	else if(orig->children()[iy]->id()==ParticleID::g \|\|
	orig->children()[iy]->id()==ParticleID::gamma) {
	foundGauge = true;
	}
	}
	radiates = foundParticle && foundGauge;
	}
	}
	if(radiates) {
	findDecayProducts(orig,hard,decay);
	}
	else if(!(**it).children().empty()\|\|
	(decaysInShower((it).id())&&!(it).dataPtr()->stable())) {
	createDecayProcess(*it,hard,decay);
	}
	else {
	hard->outgoing().push_back(make_pair(*it,PerturbativeProcessPtr()));
	}
	}
	}

	void ShowerHandler::createDecayProcess(PPtr in,PerturbativeProcessPtr hard, DecayProcessMap & decay) const {
	// there must be an incoming particle
	assert(in);
	// create the new process and connect with the parent
	PerturbativeProcessPtr newDecay=new_ptr(PerturbativeProcess());
	newDecay->incoming().push_back(make_pair(in,hard));
	Energy width=in->dataPtr()->generateWidth(in->mass());
	decay.insert(make_pair(width,newDecay));
	hard->outgoing().push_back(make_pair(in,newDecay));
	// we need to deal with the decay products if decayed
	ParticleVector children = in->children();
	if(!children.empty()) {
	for(ParticleVector::const_iterator it = children.begin();
	it!= children.end(); ++it) {
	// if decayed or should be decayed in shower make the tree
	in->abandonChild(*it);
	bool radiates = false;
	if(!(**it).children().empty()) {
	if(StandardQCDPartonMatcher::Check((**it).id())\|\|
	(LeptonMatcher::Check((it).id())&& !(abs((it).id())==ParticleID::tauminus &&
	abs((it).mass()-(it).dataPtr()->mass())<MeV))) {
	radiates = true;
	}
	else {
	bool foundParticle(false),foundGauge(false);
	for(unsigned int iy=0;iy<(**it).children().size();++iy) {
	if((it).children()[iy]->id()==(it).id()) {
	foundParticle = true;
	}
	else if((**it).children()[iy]->id()==ParticleID::g \|\|
	(**it).children()[iy]->id()==ParticleID::gamma) {
	foundGauge = true;
	}
	}
	radiates = foundParticle && foundGauge;
	}
	// finally assume all non-decaying particles are in this class
	// pr 27/11/15 not sure about this bit
	// if(!radiates) {
	// radiates = !decaysInShower((**it).id());
	// }
	}
	if(radiates) {
	findDecayProducts(*it,newDecay,decay);
	}
	else if(!(**it).children().empty()\|\|
	(decaysInShower((it).id())&&!(it).dataPtr()->stable())) {
	createDecayProcess(*it,newDecay,decay);
	}
	else {
	newDecay->outgoing().push_back(make_pair(*it,PerturbativeProcessPtr()));
	}
	}
	}
	}

	void ShowerHandler::decay(PerturbativeProcessPtr process,
	DecayProcessMap & decayMap) const {
	PPtr parent = process->incoming()[0].first;
	assert(parent);
	if(parent->spinInfo()) parent->spinInfo()->decay(true);
	unsigned int ntry = 0;
	ParticleVector children;
	while (true) {
	// exit if fails
	if (++ntry>=maxtryDecay_)
	throw Exception() << "Failed to perform decay in ShowerHandler::decay()"
	<< " after " << maxtryDecay_
	<< " attempts for " << parent->PDGName()
	<< Exception::eventerror;
	// select decay mode
	tDMPtr dm(parent->data().selectMode(*parent));
	if(!dm)
	throw Exception() << "Failed to select decay mode in ShowerHandler::decay()"
	<< "for " << parent->PDGName()
	<< Exception::eventerror;
	if(!dm->decayer())
	throw Exception() << "No Decayer for selected decay mode "
	<< " in ShowerHandler::decay()"
	<< Exception::runerror;
	// start of try block
	try {
	children = dm->decayer()->decay(dm, parent);
	// if no children have another go
	if(children.empty()) continue;
	// set up parent
	parent->decayMode(dm);
	// add children
	for (unsigned int i = 0, N = children.size(); i < N; ++i ) {
	children[i]->setLabVertex(parent->labDecayVertex());
	//parent->addChild(children[i]);
	}
	// if succeeded break out of loop
	break;
	}
	catch(Veto) {
	}
	}
	assert(!children.empty());
	for(ParticleVector::const_iterator it = children.begin();
	it!= children.end(); ++it) {
	if(!(**it).children().empty()\|\|
	(decaysInShower((it).id())&&!(it).dataPtr()->stable())) {
	createDecayProcess(*it,process,decayMap);
	}
	else {
	process->outgoing().push_back(make_pair(*it,PerturbativeProcessPtr()));
	}
	}
	}

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