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	diff --git a/include/HEJ/utility.hh b/include/HEJ/utility.hh
	index 5ad1ce3..96a1961 100644
	--- a/include/HEJ/utility.hh
	+++ b/include/HEJ/utility.hh
	@@ -1,229 +1,238 @@
	/**
	* \file
	* \brief Contains various utilities
	*/

	#pragma once

	#include <algorithm>
	#include <cassert>

	#include <boost/core/demangle.hpp>

	// FastJet Includes
	#include "fastjet/PseudoJet.hh"
	#include "fastjet/ClusterSequence.hh"

	#include "HEJ/PDG_codes.hh"

	namespace HEJ{
	//! Class representing a particle
	struct Particle {
	//! particle type
	ParticleID type;
	//! particle momentum
	fastjet::PseudoJet p;

	//! get rapidity
	double rapidity() const{
	return p.rapidity();
	}
	//! get transverse momentum
	double perp() const{
	return p.perp();
	}
	//! get momentum in x direction
	double px() const{
	return p.px();
	}
	//! get momentum in y direction
	double py() const{
	return p.py();
	}
	//! get momentum in z direction
	double pz() const{
	return p.pz();
	}
	//! get energy
	double E() const{
	return p.E();
	}
	//! get mass
	double m() const{
	return p.m();
	}
	};

	//! Functor to compare rapidities
	/**
	* This can be used whenever a rapidity comparison function is needed,
	* for example in many standard library functions.
	*
	* @see pz_less
	*/
	struct rapidity_less{
	template<class FourVector>
	bool operator()(FourVector const & p1, FourVector const & p2){
	return p1.rapidity() < p2.rapidity();
	}
	};

	//! Functor to compare momenta in z direction
	/**
	* This can be used whenever a pz comparison function is needed,
	* for example in many standard library functions.
	*
	* @see rapidity_less
	*/
	struct pz_less{
	template<class FourVector>
	bool operator()(FourVector const & p1, FourVector const & p2){
	return p1.pz() < p2.pz();
	}
	};


	//! Convert a vector of Particles to a vector of particle momenta
	inline
	std::vector<fastjet::PseudoJet> to_PseudoJet(
	std::vector<Particle> const & v
	){
	std::vector<fastjet::PseudoJet> result;
	for(auto && sp: v) result.emplace_back(sp.p);
	return result;
	}

	//! Check if a particle is a parton, i.e. quark, antiquark, or gluon
	inline
	bool is_parton(Particle const & p){
	return is_parton(p.type);
	}

	//! Check if a particle is a quark
	inline
	bool is_quark(Particle const & p){
	return is_quark(p.type);
	}

	//! Check if a particle is an anti-quark
	inline
	bool is_antiquark(Particle const & p){
	return is_antiquark(p.type);
	}

	//! Check if a particle is a quark or any-quark
	inline
	bool is_anyquark(Particle const & p){
	return is_anyquark(p.type);
	}

	//! Check if a particle is a photon, W or Z boson
	inline bool is_AWZ_boson(Particle const & particle){
	return is_AWZ_boson(particle.type);
	}

	//! Check if a particle is a photon, W, Z, or Higgs boson
	inline bool is_AWZH_boson(Particle const & particle){
	return is_AWZH_boson(particle.type);
	}

	//! Extract all partons from a vector of particles
	inline
	std::vector<Particle> filter_partons(
	std::vector<Particle> const & v
	){
	std::vector<Particle> result;
	result.reserve(v.size());
	std::copy_if(
	begin(v), end(v), std::back_inserter(result),
	[](Particle const & p){ return is_parton(p); }
	);
	return result;
	}

	//! Create a std::unique_ptr to a T object
	/**
	* For non-array types this works like std::make_unique,
	* which is not available under C++11
	*/
	template<class T, class... Args>
	std::unique_ptr<T> make_unique(Args&&... a){
	return std::unique_ptr<T>{new T{std::forward<Args>(a)...}};
	}

	//! Create an array containing the passed arguments
	template<typename T, typename... U>
	constexpr
	std::array<T, 1 + sizeof...(U)> make_array(T t, U&&... rest){
	return {{t, std::forward<U>(rest)...}};
	}


	inline
	std::string join(
	std::string const & /* delim */
	){
	return "";
	}

	inline
	std::string join(
	std::string const & /* delim */, std::string const & str
	){
	return str;
	}

	//! Join strings with a delimiter
	/**
	* @param delim Delimiter to be put between consecutive strings
	* @param first First string
	* @param second Second string
	* @param rest Remaining strings
	*/
	template<typename... Strings>
	std::string join(
	std::string const & delim,
	std::string const & first, std::string const & second,
	Strings&&... rest
	){
	return join(delim, first + delim + second, std::forward<Strings>(rest)...);
	}

	//! Return the name of the argument's type
	template<typename T>
	std::string type_string(T&&){
	return boost::core::demangle(typeid(T).name());
	}

	//! Eliminate compiler warnings for unused variables
	template<typename... T>
	constexpr void ignore(T&&...) {}

	//! Check whether two doubles are closer than ep > 0 to each other
	inline
	bool nearby_ep(double a, double b, double ep){
	assert(ep > 0);
	return std::abs(a-b) < ep;
	}

	//! Check whether all components of two PseudoJets are closer than ep to each other
	inline
	bool nearby_ep(
	fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb,
	double ep
	){
	assert(ep > 0);
	for(size_t i = 0; i < 4; ++i){
	if(!nearby_ep(pa[i], pb[i], ep)) return false;
	}
	return true;
	}

	inline
	bool nearby(
	fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb, double const norm = 1.
	){
	return nearby_ep(pa, pb, 1e-7*norm);
	}

	+ //! Check whether two rapidities are close
	+ inline
	+ bool nearby_rap(
	+ double rapa, double rapb, double rap
	+ ){
	+ assert(rap > 0);
	+ if(!nearby_ep(rapa, rapb, rap)) return false;
	+ return true;
	+ }
	}
	diff --git a/src/Event.cc b/src/Event.cc
	index 1caf80f..21744ed 100644
	--- a/src/Event.cc
	+++ b/src/Event.cc
	@@ -1,650 +1,649 @@
	#include "HEJ/Event.hh"

	#include "HEJ/utility.hh"

	namespace HEJ{

	namespace{
	constexpr int status_in = -1;
	constexpr int status_decayed = 2;
	constexpr int status_out = 1;

	/// @name helper functions to determine event type
	//@{

	/**
	* \brief check if final state valid for HEJ
	*
	* check if there is at most one photon, W, H, Z in the final state
	* and all the rest are quarks or gluons
	*/
	bool final_state_ok(std::vector<Particle> const & outgoing){
	bool has_AWZH_boson = false;
	for(auto const & out: outgoing){
	if(is_AWZH_boson(out.type)){
	if(has_AWZH_boson) return false;
	has_AWZH_boson = true;
	}
	else if(! is_parton(out.type)) return false;
	}
	return true;
	}

	template<class Iterator>
	Iterator remove_AWZH(Iterator begin, Iterator end){
	return std::remove_if(
	begin, end, [](Particle const & p){return is_AWZH_boson(p);}
	);
	}

	template<class Iterator>
	bool valid_outgoing(Iterator begin, Iterator end){
	return std::distance(begin, end) >= 2
	&& std::is_sorted(begin, end, rapidity_less{})
	&& std::count_if(
	begin, end, [](Particle const & s){return is_AWZH_boson(s);}
	) < 2;
	}

	/**
	* \brief function which determines if type change is consistent with W emission.
	* @param in incoming Particle
	* @param out outgoing Particle
	*
	* Ensures that change type of quark line is possible by a flavour changing
	* W emission.
	*/
	bool is_W_Current(ParticleID in, ParticleID out){
	if((in==1 && out==2)\|\|(in==2 && out==1)){
	return true;
	}
	else if((in==-1 && out==-2)\|\|(in==-2 && out==-1)){
	return true;
	}
	else if((in==3 && out==4)\|\|(in==4 && out==3)){
	return true;
	}
	else if((in==-3 && out==-4)\|\|(in==-4 && out==-3)){
	return true;
	}
	else{
	return false;
	}
	}

	/**
	* \brief checks if particle type remains same from incoming to outgoing
	* @param in incoming Particle
	* @param out outgoing Particle
	*/
	bool is_Pure_Current(ParticleID in, ParticleID out){
	if(abs(in)<=6 \|\| in==21) return (in==out);
	else return false;
	}


	// @note that this changes the outgoing range!
	template<class ConstIterator, class Iterator>
	bool is_FKL(
	ConstIterator begin_incoming, ConstIterator end_incoming,
	Iterator begin_outgoing, Iterator end_outgoing
	){
	assert(std::distance(begin_incoming, end_incoming) == 2);
	assert(std::distance(begin_outgoing, end_outgoing) >= 2);

	// One photon, W, H, Z in the final state is allowed.
	// Remove it for remaining tests,
	end_outgoing = remove_AWZH(begin_outgoing, end_outgoing);

	if(std::all_of(
	begin_outgoing + 1, end_outgoing - 1,
	[](Particle const & p){ return p.type == pid::gluon; })
	){
	// Test if this is a standard FKL configuration.
	if (is_Pure_Current(begin_incoming->type, begin_outgoing->type)
	&& is_Pure_Current((end_incoming-1)->type, (end_outgoing-1)->type)){
	return true;
	}
	}
	return false;
	}

	template<class ConstIterator, class Iterator>
	bool is_W_FKL(
	ConstIterator begin_incoming, ConstIterator end_incoming,
	Iterator begin_outgoing, Iterator end_outgoing
	){
	assert(std::distance(begin_incoming, end_incoming) == 2);
	assert(std::distance(begin_outgoing, end_outgoing) >= 2);

	// One photon, W, H, Z in the final state is allowed.
	// Remove it for remaining tests,
	end_outgoing = remove_AWZH(begin_outgoing, end_outgoing);

	if(std::all_of(
	begin_outgoing + 1, end_outgoing - 1,
	[](Particle const & p){ return p.type == pid::gluon; })
	){
	// Test if this is a standard FKL configuration.
	if(is_W_Current(begin_incoming->type, begin_outgoing->type)
	&& is_Pure_Current((end_incoming-1)->type, (end_outgoing-1)->type)){
	return true;
	}
	else if(is_Pure_Current(begin_incoming->type, begin_outgoing->type)
	&& is_W_Current((end_incoming-1)->type, (end_outgoing-1)->type)){
	return true;
	}
	}
	return false;
	}

	bool is_FKL(
	std::array<Particle, 2> const & incoming,
	std::vector<Particle> outgoing
	){
	assert(std::is_sorted(begin(incoming), end(incoming), pz_less{}));
	assert(valid_outgoing(begin(outgoing), end(outgoing)));

	const auto WEmit = std::find_if(
	begin(outgoing), end(outgoing),
	[](Particle const & s){ return abs(s.type) == pid::Wp; }
	);

	if (abs(WEmit->type) == pid::Wp){
	return is_W_FKL(
	begin(incoming), end(incoming),
	begin(outgoing), end(outgoing)
	);
	}
	else{
	return is_FKL(
	begin(incoming), end(incoming),
	begin(outgoing), end(outgoing)
	);
	}
	}

	bool has_2_jets(Event const & event){
	return event.jets().size() >= 2;
	}

	/**
	* \brief Checks whether event is unordered backwards
	* @param ev Event
	* @returns Is Event Unordered Backwards
	*
	* - Checks there is more than 3 constuents in the final state
	* - Checks there is more than 3 jets
	* - Checks the most backwards parton is a gluon
	* - Checks the most forwards jet is not a gluon
	* - Checks the rest of the event is FKL
	* - Checks the second most backwards is not a different boson
	* - Checks the unordered gluon actually forms a jet
	*/
	bool is_unordered_backward(Event const & ev){
	auto const & in = ev.incoming();
	auto const & out = ev.outgoing();
	assert(std::is_sorted(begin(in), end(in), pz_less{}));
	assert(valid_outgoing(begin(out), end(out)));

	if(out.size() < 3) return false;
	if(ev.jets().size() < 3) return false;
	if(in.front().type == pid::gluon) return false;
	if(out.front().type != pid::gluon) return false;
	// When skipping the unordered emission
	// the remainder should be a regular FKL event,
	// except that the (new) first outgoing particle must not be a A,W,Z,H.
	const auto FKL_begin = next(begin(out));
	if(is_AWZH_boson(*FKL_begin)) return false;
	if(!is_FKL(in, {FKL_begin, end(out)})) return false;
	// check that the unordered gluon forms an extra jet
	const auto jets = sorted_by_rapidity(ev.jets());
	const auto indices = ev.particle_jet_indices({jets.front()});
	return indices[0] >= 0 && indices[1] == -1;
	}

	/**
	* \brief Checks for a forward unordered gluon emission
	* @param ev Event
	* @returns Is the event a forward unordered emission
	*
	* \see is_unordered_backward
	*/
	bool is_unordered_forward(Event const & ev){
	auto const & in = ev.incoming();
	auto const & out = ev.outgoing();
	assert(std::is_sorted(begin(in), end(in), pz_less{}));
	assert(valid_outgoing(begin(out), end(out)));

	if(out.size() < 3) return false;
	if(ev.jets().size() < 3) return false;
	if(in.back().type == pid::gluon) return false;
	if(out.back().type != pid::gluon) return false;
	// When skipping the unordered emission
	// the remainder should be a regular FKL event,
	// except that the (new) last outgoing particle must not be a A,W,Z,H.
	const auto FKL_end = prev(end(out));
	if(is_AWZH_boson(*prev(FKL_end))) return false;
	if(!is_FKL(in, {begin(out), FKL_end})) return false;
	// check that the unordered gluon forms an extra jet
	const auto jets = sorted_by_rapidity(ev.jets());
	const auto indices = ev.particle_jet_indices({jets.back()});
	return indices.back() >= 0 && indices[indices.size()-2] == -1;
	}


	/**
	* \brief Checks for a forward extremal qqx
	* @param ev Event
	* @returns Is the event a forward extremal qqx event
	*
	* Checks there is 3 or more than 3 constituents in the final state
	* Checks there is 3 or more than 3 jets
	* Checks most forwards incoming is gluon
	* Checks most extremal particle is not a Higgs (either direction)
	* Checks the second most forwards particle is not Higgs boson
	* Checks the most forwards parton is a either quark or anti-quark.
	* Checks the second most forwards parton is anti-quark or quark.
	* Checks the qqbar pair form 2 separate jets.
	*/
	bool is_Ex_qqxf(Event const & ev){
	auto const & in = ev.incoming();
	auto const & out = ev.outgoing();
	assert(std::is_sorted(begin(in), end(in), pz_less{}));
	assert(valid_outgoing(begin(out), end(out)));

	int fkl_end=2;

	if(out.size() < 3) return false;
	if(ev.jets().size() < 3) return false;
	if(in.back().type != pid::gluon) return false;
	if(out.back().type == pid::Higgs \|\| out.front().type == pid::Higgs
	\|\| out.rbegin()[1].type == pid::Higgs) return false;

	// if extremal AWZ
	if(is_AWZ_boson(out.back())){ // if extremal AWZ
	fkl_end++;
	if (is_quark(out.rbegin()[1])){ //if second quark
	if (!(is_antiquark(out.rbegin()[2]))) return false;// third must be anti-quark
	}
	else if (is_antiquark(out.rbegin()[1])){ //if second anti-quark
	if (!(is_quark(out.rbegin()[2]))) return false;// third must be quark
	}
	else return false;
	}
	else if (is_quark(out.rbegin()[0])){ //if extremal quark
	if(is_AWZ_boson(out.rbegin()[1])){ // if second AWZ
	fkl_end++;
	if (!(is_antiquark(out.rbegin()[2]))) return false;// third must be anti-quark
	}
	else if (!(is_antiquark(out.rbegin()[1]))) return false;// second must be anti-quark
	}
	else if (is_antiquark(out.rbegin()[0])){ //if extremal anti-quark
	if(is_AWZ_boson(out.rbegin()[1])){ // if second AWZ
	fkl_end++;
	if (!(is_quark(out.rbegin()[2]))) return false;// third must be quark
	}
	else if (!(is_quark(out.rbegin()[1]))) return false;// second must be quark
	}
	else return false;

	// When skipping the qqbar
	// New last outgoing particle must not be a Higgs
	if (out.rbegin()[fkl_end].type == pid::Higgs) return false;

	const auto jets = fastjet::sorted_by_rapidity(ev.jets());
	const auto indices = ev.particle_jet_indices({jets});

	// Ensure qqbar pair are in separate jets
	if(indices[indices.size()-2] != indices[indices.size()-1]-1) return false;

	// Opposite current should be logical to process
	if (is_AWZ_boson(out.front().type)){
	return (is_Pure_Current(in.front().type, out[1].type)
	\|\| is_W_Current(in.front().type,out[1].type));
	}
	else
	return (is_Pure_Current(in.front().type, out[0].type)
	\|\| is_W_Current(in.front().type,out[0].type));
	}

	/**
	* \brief Checks for a backward extremal qqx
	* @param ev Event
	* @returns Is the event a backward extremal qqx event
	*
	* Checks there is 3 or more than 3 constituents in the final state
	* Checks there is 3 or more than 3 jets
	* Checks most backwards incoming is gluon
	* Checks most extremal particle is not a Higgs (either direction) y
	* Checks the second most backwards particle is not Higgs boson y
	* Checks the most backwards parton is a either quark or anti-quark. y
	* Checks the second most backwards parton is anti-quark or quark. y
	* Checks the qqbar pair form 2 separate jets.
	*/
	bool is_Ex_qqxb(Event const & ev){
	auto const & in = ev.incoming();
	auto const & out = ev.outgoing();
	assert(std::is_sorted(begin(in), end(in), pz_less{}));
	assert(valid_outgoing(begin(out), end(out)));

	int fkl_start=2;

	if(out.size() < 3) return false;
	if(ev.jets().size() < 3) return false;
	if(in.front().type != pid::gluon) return false;
	if(out.back().type == pid::Higgs \|\| out.front().type == pid::Higgs
	\|\| out[1].type == pid::Higgs) return false;

	if(is_AWZ_boson(out.front())){ // if extremal AWZ
	fkl_start++;
	if (is_quark(out[1])){ //if second quark
	if (!(is_antiquark(out[2]))) return false;// third must be anti-quark
	}
	else if (is_antiquark(out[1])){ //if second anti-quark
	if (!(is_quark(out[2]))) return false;// third must be quark
	}
	else return false;
	}
	else if (is_quark(out[0])){ // if extremal quark
	if(is_AWZ_boson(out[1])){ // if second AWZ
	fkl_start++;
	if (!(is_antiquark(out[2]))) return false;// third must be anti-quark
	}
	else if (!(is_antiquark(out[1]))) return false;// second must be anti-quark
	}
	else if (is_antiquark(out[0])){ //if extremal anti-quark
	if(is_AWZ_boson(out[1])){ // if second AWZ
	fkl_start++;
	if (!(is_quark(out[2]))) return false;// third must be quark
	}
	else if (!(is_quark(out[1]))) return false;// second must be quark
	}
	else return false;

	// When skipping the qqbar
	// New last outgoing particle must not be a Higgs.
	if (out[fkl_start].type == pid::Higgs) return false;

	const auto jets = fastjet::sorted_by_rapidity(ev.jets());
	const auto indices = ev.particle_jet_indices({jets});

	// Ensure qqbar pair form separate jets.
	if(indices[0] != indices[1]-1) return false;

	// Other current should be logical to process
	if (is_AWZ_boson(out.back())){
	return (is_Pure_Current(in.back().type, out.rbegin()[1].type)
	\|\| is_W_Current(in.back().type,out.rbegin()[1].type));
	}
	else
	return (is_Pure_Current(in.back().type, out.rbegin()[0].type)
	\|\| is_W_Current(in.back().type, out.rbegin()[0].type));
	}


	/**
	* \brief Checks for a central qqx
	* @param ev Event
	* @returns Is the event a central extremal qqx event
	*
	* Checks there is 4 or more than 4 constuents in the final state
	* Checks there is 4 or more than 4 jets
	* Checks most extremal particle is not a Higgs (either direction) y
	* Checks for a central quark in the outgoing states
	* Checks for adjacent anti-quark parton. (allowing for AWZ boson emission between)
	* Checks external currents are logically sound.
	*/
	bool is_Mid_qqx(Event const & ev){
	auto const & in = ev.incoming();
	auto const & out = ev.outgoing();
	assert(std::is_sorted(begin(in), end(in), pz_less{}));
	assert(valid_outgoing(begin(out), end(out)));

	if(out.size() < 4) return false;
	if(ev.jets().size() < 4) return false;

	if(out.back().type == pid::Higgs \|\| out.front().type == pid::Higgs)
	return false;

	size_t start_FKL=0;
	size_t end_FKL=0;

	if (is_AWZ_boson(out.back())){
	end_FKL++;
	}
	if (is_AWZ_boson(out.front())){
	start_FKL++;
	}

	if ((is_Pure_Current(in.back().type,out.rbegin()[end_FKL].type)
	&& is_Pure_Current(in.front().type,out[start_FKL].type))){
	//nothing to do
	}
	else if (is_W_Current(in.back().type,out.rbegin()[end_FKL].type)
	&& is_Pure_Current(in.front().type,out[start_FKL].type)){
	//nothing to do
	}
	else if (!(is_Pure_Current(in.back().type,out.rbegin()[end_FKL].type)
	&& is_W_Current(in.front().type,out[start_FKL].type))){
	return false;
	}

	- for(size_t i=1+start_FKL; i<out.size()-1-end_FKL;i++){
	- if (is_quark(out[i])){
	- if ((is_antiquark(out[i-1]) && i!=1)
	- \|\| (is_antiquark(out[i+1]) && i!=out.size()-1-end_FKL))
	- return true;
	- else if (is_AWZ_boson(out[i-1]) && (is_antiquark(out[i-2]) && i!=2) )
	- return true;
	- else if (is_AWZ_boson(out[i+1]) && (is_antiquark(out[i+2]) && i!=out.size()-2) )
	- return true;
	+ const auto jets = fastjet::sorted_by_rapidity(ev.jets());
	+ const auto indices = ev.particle_jet_indices({jets});
	+ auto const out_partons = filter_partons(out);
	+
	+ for (size_t i = 1; i<out_partons.size()-2; i++){
	+ if ((is_quark(out_partons[i]) && (is_antiquark(out_partons[i+1])))
	+ \|\| (is_antiquark(out_partons[i]) && (is_quark(out_partons[i+1])))){
	+ return (indices[i+1] == indices[i]+1 && indices[i] != -1);
	}
	}
	return false;
	}

	using event_type::EventType;

	EventType classify(Event const & ev){
	if(! final_state_ok(ev.outgoing()))
	return EventType::bad_final_state;
	if(! has_2_jets(ev))
	return EventType::no_2_jets;
	if(is_FKL(ev.incoming(), ev.outgoing()))
	return EventType::FKL;
	if(is_unordered_backward(ev))
	return EventType::unordered_backward;
	if(is_unordered_forward(ev))
	return EventType::unordered_forward;
	if(is_Ex_qqxb(ev))
	return EventType::extremal_qqxb;
	if(is_Ex_qqxf(ev))
	return EventType::extremal_qqxf;
	if(is_Mid_qqx(ev))
	return EventType::central_qqx;
	return EventType::nonHEJ;
	}
	//@}

	Particle extract_particle(LHEF::HEPEUP const & hepeup, int i){
	return Particle{
	static_cast<ParticleID>(hepeup.IDUP[i]),
	fastjet::PseudoJet{
	hepeup.PUP[i][0], hepeup.PUP[i][1],
	hepeup.PUP[i][2], hepeup.PUP[i][3]
	}
	};
	}

	bool is_decay_product(std::pair<int, int> const & mothers){
	if(mothers.first == 0) return false;
	return mothers.second == 0 \|\| mothers.first == mothers.second;
	}

	} // namespace anonymous

	UnclusteredEvent::UnclusteredEvent(LHEF::HEPEUP const & hepeup):
	central(EventParameters{
	hepeup.scales.mur, hepeup.scales.muf, hepeup.weight()
	})
	{
	size_t in_idx = 0;
	for (int i = 0; i < hepeup.NUP; ++i) {
	// skip decay products
	// we will add them later on, but we have to ensure that
	// the decayed particle is added before
	if(is_decay_product(hepeup.MOTHUP[i])) continue;

	auto particle = extract_particle(hepeup, i);
	// needed to identify mother particles for decay products
	particle.p.set_user_index(i+1);

	if(hepeup.ISTUP[i] == status_in){
	if(in_idx > incoming.size()) {
	throw std::invalid_argument{
	"Event has too many incoming particles"
	};
	}
	incoming[in_idx++] = std::move(particle);
	}
	else outgoing.emplace_back(std::move(particle));
	}
	std::sort(
	begin(incoming), end(incoming),
	[](Particle o1, Particle o2){return o1.p.pz()<o2.p.pz();}
	);
	std::sort(begin(outgoing), end(outgoing), rapidity_less{});

	// add decay products
	for (int i = 0; i < hepeup.NUP; ++i) {
	if(!is_decay_product(hepeup.MOTHUP[i])) continue;
	const int mother_id = hepeup.MOTHUP[i].first;
	const auto mother = std::find_if(
	begin(outgoing), end(outgoing),
	[mother_id](Particle const & particle){
	return particle.p.user_index() == mother_id;
	}
	);
	if(mother == end(outgoing)){
	throw std::invalid_argument{"invalid decay product parent"};
	}
	const int mother_idx = std::distance(begin(outgoing), mother);
	assert(mother_idx >= 0);
	decays[mother_idx].emplace_back(extract_particle(hepeup, i));
	}
	}

	Event::Event(
	UnclusteredEvent ev,
	fastjet::JetDefinition const & jet_def, double min_jet_pt
	):
	ev_{std::move(ev)},
	cs_{to_PseudoJet(filter_partons(ev_.outgoing)), jet_def},
	min_jet_pt_{min_jet_pt}
	{
	type_ = classify(*this);
	}

	std::vector<fastjet::PseudoJet> Event::jets() const{
	return cs_.inclusive_jets(min_jet_pt_);
	}

	/**
	* \brief Returns the invarient mass of the event
	* @param ev Event
	* @returns s hat
	*
	* Makes use of the FastJet PseudoJet function m2().
	* Applies this function to the sum of the incoming partons.
	*/
	double shat(Event const & ev){
	return (ev.incoming()[0].p + ev.incoming()[1].p).m2();
	}

	namespace{
	// colour flow according to Les Houches standard
	// TODO: stub
	std::vector<std::pair<int, int>> colour_flow(
	std::array<Particle, 2> const & incoming,
	std::vector<Particle> const & outgoing
	){
	std::vector<std::pair<int, int>> result(
	incoming.size() + outgoing.size()
	);
	for(auto & col: result){
	col = std::make_pair(-1, -1);
	}
	return result;
	}
	}

	LHEF::HEPEUP to_HEPEUP(Event const & event, LHEF::HEPRUP * heprup){
	LHEF::HEPEUP result;
	result.heprup = heprup;
	result.weights = {{event.central().weight, nullptr}};
	for(auto const & var: event.variations()){
	result.weights.emplace_back(var.weight, nullptr);
	}
	size_t num_particles = event.incoming().size() + event.outgoing().size();
	for(auto const & decay: event.decays()) num_particles += decay.second.size();
	result.NUP = num_particles;
	// the following entries are pretty much meaningless
	result.IDPRUP = event.type()+1; // event ID
	result.AQEDUP = 1./128.; // alpha_EW
	//result.AQCDUP = 0.118 // alpha_QCD
	// end meaningless part
	result.XWGTUP = event.central().weight;
	result.SCALUP = event.central().muf;
	result.scales.muf = event.central().muf;
	result.scales.mur = event.central().mur;
	result.scales.SCALUP = event.central().muf;
	result.pdfinfo.p1 = event.incoming().front().type;
	result.pdfinfo.p2 = event.incoming().back().type;
	result.pdfinfo.scale = event.central().muf;
	for(Particle const & in: event.incoming()){
	result.IDUP.emplace_back(in.type);
	result.ISTUP.emplace_back(status_in);
	result.PUP.push_back({in.p[0], in.p[1], in.p[2], in.p[3], in.p.m()});
	result.MOTHUP.emplace_back(0, 0);
	}
	for(size_t i = 0; i < event.outgoing().size(); ++i){
	Particle const & out = event.outgoing()[i];
	result.IDUP.emplace_back(out.type);
	const int status = event.decays().count(i)?status_decayed:status_out;
	result.ISTUP.emplace_back(status);
	result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
	result.MOTHUP.emplace_back(1, 2);
	}
	result.ICOLUP = colour_flow(
	event.incoming(), filter_partons(event.outgoing())
	);
	if(result.ICOLUP.size() < num_particles){
	const size_t AWZH_boson_idx = std::find_if(
	begin(event.outgoing()), end(event.outgoing()),
	[](Particle const & s){ return is_AWZH_boson(s); }
	) - begin(event.outgoing()) + event.incoming().size();
	assert(AWZH_boson_idx <= result.ICOLUP.size());
	result.ICOLUP.insert(
	begin(result.ICOLUP) + AWZH_boson_idx,
	std::make_pair(0,0)
	);
	}
	for(auto const & decay: event.decays()){
	for(auto const out: decay.second){
	result.IDUP.emplace_back(out.type);
	result.ISTUP.emplace_back(status_out);
	result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
	const size_t mother_idx = 1 + event.incoming().size() + decay.first;
	result.MOTHUP.emplace_back(mother_idx, mother_idx);
	result.ICOLUP.emplace_back(0,0);
	}
	}
	assert(result.ICOLUP.size() == num_particles);
	static constexpr double unknown_spin = 9.; //per Les Houches accord
	result.VTIMUP = std::vector<double>(num_particles, unknown_spin);
	result.SPINUP = result.VTIMUP;
	return result;
	}

	}
	diff --git a/src/PhaseSpacePoint.cc b/src/PhaseSpacePoint.cc
	index c093ceb..d10f254 100644
	--- a/src/PhaseSpacePoint.cc
	+++ b/src/PhaseSpacePoint.cc
	@@ -1,595 +1,602 @@
	#include "HEJ/PhaseSpacePoint.hh"

	#include <random>

	#include <CLHEP/Random/Randomize.h>
	#include <CLHEP/Random/RanluxEngine.h>

	#include "HEJ/Constants.hh"
	#include "HEJ/resummation_jet.hh"
	#include "HEJ/utility.hh"
	#include "HEJ/kinematics.hh"

	namespace HEJ{
	namespace {
	constexpr int max_jet_user_idx = PhaseSpacePoint::ng_max;

	bool is_nonjet_parton(fastjet::PseudoJet const & parton){
	assert(parton.user_index() != -1);
	return parton.user_index() > max_jet_user_idx;
	}

	bool is_jet_parton(fastjet::PseudoJet const & parton){
	assert(parton.user_index() != -1);
	return parton.user_index() <= max_jet_user_idx;
	}

	// user indices for partons with extremal rapidity
	constexpr int qqxb_idx = -7;
	constexpr int qqxf_idx = -6;
	constexpr int unob_idx = -5;
	constexpr int unof_idx = -4;
	constexpr int backward_FKL_idx = -3;
	constexpr int forward_FKL_idx = -2;
	}

	namespace {
	double estimate_ng_mean(std::vector<fastjet::PseudoJet> const & Born_jets){
	const double delta_y =
	Born_jets.back().rapidity() - Born_jets.front().rapidity();
	assert(delta_y > 0);
	// Formula derived from fit in arXiv:1805.04446 (see Fig. 2)
	return 0.975052*delta_y;
	}
	}

	std::vector<fastjet::PseudoJet> PhaseSpacePoint::cluster_jets(
	std::vector<fastjet::PseudoJet> const & partons
	) const{
	fastjet::ClusterSequence cs(partons, param_.jet_param.def);
	return cs.inclusive_jets(param_.jet_param.min_pt);
	}

	bool PhaseSpacePoint::pass_resummation_cuts(
	std::vector<fastjet::PseudoJet> const & jets
	) const{
	return cluster_jets(jets).size() == jets.size();
	}

	int PhaseSpacePoint::sample_ng(std::vector<fastjet::PseudoJet> const & Born_jets){
	const double ng_mean = estimate_ng_mean(Born_jets);
	std::poisson_distribution<int> dist(ng_mean);
	const int ng = dist(ran_.get());
	assert(ng >= 0);
	assert(ng < ng_max);
	weight_ = std::tgamma(ng + 1)std::exp(ng_mean)*std::pow(ng_mean, -ng);
	return ng;
	}

	void PhaseSpacePoint::copy_AWZH_boson_from(Event const & event){
	auto const & from = event.outgoing();

	const auto AWZH_boson = std::find_if(
	begin(from), end(from),
	[](Particle const & p){ return is_AWZH_boson(p); }
	);
	if(AWZH_boson == end(from)) return;
	auto insertion_point = std::lower_bound(
	begin(outgoing_), end(outgoing_), *AWZH_boson, rapidity_less{}
	);
	outgoing_.insert(insertion_point, *AWZH_boson);

	// copy decay products
	const int idx = std::distance(begin(from), AWZH_boson);
	assert(idx >= 0);
	const auto decay_it = event.decays().find(idx);
	if(decay_it != end(event.decays())){
	const int new_idx = std::distance(begin(outgoing_), insertion_point);
	assert(new_idx >= 0);
	assert(outgoing_[new_idx].type == AWZH_boson->type);
	decays_.emplace(new_idx, decay_it->second);
	}

	assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
	}


	//! \brief relabels qqx-pair with its PDG IDs.
	//*@param ev Born Event
	//
	// This function will label the qqx pair in a qqx event back to
	// their original types from the input event.
	- // @TODO: Central qqx only works with 4j input and not higher!
	void PhaseSpacePoint::label_qqx(Event const & event){
	auto const & bornout = event.outgoing();
	const auto backquark = std::find_if(
	begin(bornout) + 1 - ((qqxb_)?1:0), end(bornout) - 1 + ((qqxf_)?1:0) ,
	[](Particle const & s){ return (s.type != pid::gluon && is_parton(s.type)); }
	);
	- if(backquark == end(bornout)) {
	- weight_=0;
	- return;
	- }
	+ assert(backquark->type !=pid::gluon);
	+ if(backquark == end(bornout) \|\| (backquark+1)->type==pid::gluon) weight_= 0;
	+
	auto partons = to_PseudoJet(filter_partons(outgoing_));
	fastjet::ClusterSequence cs(partons, event.jet_def());
	const auto jets = fastjet::sorted_by_rapidity(cs.inclusive_jets(event.min_jet_pt()));
	assert(jets.size() >= (3u + qqxmid_));
	- const auto indices = cs.particle_jet_indices({jets});
	- int pqjet = 0 + qqxmid_ + qqxf_*(jets.size()-2);

	- bool jetsadjacent = false;
	+ const auto indices = cs.particle_jet_indices({jets});
	assert(partons.size() == indices.size());
	- for (size_t i = 0; i<indices.size()-1; i++){
	- if (indices[i]==(pqjet) && indices[i+1] == pqjet+1){
	- outgoing_.at(i).type = backquark->type;
	- outgoing_.at(i+1).type = (backquark+1)->type;
	- jetsadjacent = true;
	- break;
	+
	+ int qpart=0;
	+ // Find Parton in res event closest to most backward qqx jet in born
	+ for (size_t i=0; i<indices.size(); i++){
	+ if( (indices[i] != -1) && indices[i]!=indices[i+1]
	+ && nearby_rap(backquark->rapidity(), partons[i].rapidity(), 0.1)){
	+ qpart=i;
	}
	}
	- if (!jetsadjacent) weight_=0;
	+
	+ if (indices[qpart] == -1) weight_= 0;
	+ else if (indices[qpart] == 0 && (!qqxb_)) weight_=0;
	+ else if (indices[qpart] == signed(jets.size()-2) && (!qqxf_)) weight_=0;
	+
	+ // Ensure qqx in separate jets and adjacent in rapidity
	+ if (indices[qpart] == indices[qpart+1]-1){
	+ outgoing_.at(qpart).type = backquark->type;
	+ outgoing_.at(qpart+1).type = (backquark+1)->type;
	+ }
	+ else weight_=0;
	assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
	}

	PhaseSpacePoint::PhaseSpacePoint(
	Event const & ev, PhaseSpacePointConfig conf, HEJ::RNG & ran
	):
	unob_{ev.type() == event_type::unob},
	unof_{ev.type() == event_type::unof},
	qqxb_{ev.type() == event_type::qqxexb},
	qqxf_{ev.type() == event_type::qqxexf},
	qqxmid_{ev.type() == event_type::qqxmid},
	param_{std::move(conf)},
	ran_{ran}
	{
	weight_ = 1;
	const auto Born_jets = sorted_by_rapidity(ev.jets());
	const int ng = sample_ng(Born_jets);
	weight_ /= std::tgamma(ng + 1);
	const int ng_jets = sample_ng_jets(ng, Born_jets);
	std::vector<fastjet::PseudoJet> out_partons = gen_non_jet(
	ng - ng_jets, CMINPT, param_.jet_param.min_pt
	);

	const auto qperp = std::accumulate(
	begin(out_partons), end(out_partons),
	fastjet::PseudoJet{}
	);
	const auto jets = reshuffle(Born_jets, qperp);
	if(weight_ == 0.) return;
	if(! pass_resummation_cuts(jets)){
	weight_ = 0.;
	return;
	}
	std::vector<fastjet::PseudoJet> jet_partons = split(jets, ng_jets);
	if(weight_ == 0.) return;
	rescale_rapidities(
	out_partons,
	most_backward_FKL(jet_partons).rapidity(),
	most_forward_FKL(jet_partons).rapidity()
	);
	if(! cluster_jets(out_partons).empty()){
	weight_ = 0.;
	return;
	}
	std::sort(begin(out_partons), end(out_partons), rapidity_less{});
	assert(
	std::is_sorted(begin(jet_partons), end(jet_partons), rapidity_less{})
	);
	const auto first_jet_parton = out_partons.insert(
	end(out_partons), begin(jet_partons), end(jet_partons)
	);
	std::inplace_merge(
	begin(out_partons), first_jet_parton, end(out_partons), rapidity_less{}
	);

	if(! jets_ok(Born_jets, out_partons)){
	weight_ = 0.;
	return;
	}
	weight_ *= phase_space_normalisation(Born_jets.size(), out_partons.size());

	outgoing_.reserve(out_partons.size() + 1); // one slot for possible A, W, Z, H
	for(auto & p: out_partons){
	outgoing_.emplace_back(Particle{pid::gluon, std::move(p)});
	}
	most_backward_FKL(outgoing_).type = ev.incoming().front().type;
	most_forward_FKL(outgoing_).type = ev.incoming().back().type;
	if(qqxmid_\|\|qqxb_\|\|qqxf_){
	label_qqx(ev);
	}
	copy_AWZH_boson_from(ev);

	assert(!outgoing_.empty());

	reconstruct_incoming(ev.incoming());
	}

	std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_non_jet(
	int count, double ptmin, double ptmax
	){
	// heuristic parameters for pt sampling
	const double ptpar = 1.3 + count/5.;
	const double temp1 = atan((ptmax - ptmin)/ptpar);

	std::vector<fastjet::PseudoJet> partons(count);
	for(size_t i = 0; i < (size_t) count; ++i){
	const double r1 = ran_.get().flat();
	const double pt = ptmin + ptpartan(r1temp1);
	const double temp2 = cos(r1*temp1);
	const double phi = 2M_PIran_.get().flat();
	weight_ = 2.0M_PIptptpartemp1/(temp2temp2);
	// we don't know the allowed rapidity span yet,
	// set a random value to be rescaled later on
	const double y = ran_.get().flat();
	partons[i].reset_PtYPhiM(pt, y, phi);
	// Set user index higher than any jet-parton index
	// in order to assert that these are not inside jets
	partons[i].set_user_index(i + 1 + ng_max);

	assert(ptmin-1e-5 <= partons[i].pt() && partons[i].pt() <= ptmax+1e-5);
	}
	assert(std::all_of(partons.cbegin(), partons.cend(), is_nonjet_parton));
	return partons;
	}

	void PhaseSpacePoint::rescale_rapidities(
	std::vector<fastjet::PseudoJet> & partons,
	double ymin, double ymax
	){
	constexpr double ep = 1e-7;
	for(auto & parton: partons){
	assert(0 <= parton.rapidity() && parton.rapidity() <= 1);
	const double dy = ymax - ymin - 2*ep;
	const double y = ymin + ep + dy*parton.rapidity();
	parton.reset_momentum_PtYPhiM(parton.pt(), y, parton.phi());
	weight_ *= dy;
	assert(ymin <= parton.rapidity() && parton.rapidity() <= ymax);
	}
	}

	namespace {
	template<typename T, typename... Rest>
	auto min(T const & a, T const & b, Rest&&... r) {
	using std::min;
	return min(a, min(b, std::forward<Rest>(r)...));
	}
	}

	double PhaseSpacePoint::probability_in_jet(
	std::vector<fastjet::PseudoJet> const & Born_jets
	) const{
	assert(std::is_sorted(begin(Born_jets), end(Born_jets), rapidity_less{}));
	assert(Born_jets.size() >= 2);

	const double dy =
	Born_jets.back().rapidity() - Born_jets.front().rapidity();
	const double R = param_.jet_param.def.R();
	const int njets = Born_jets.size();
	const double p_J_y_large = (njets-1)RR/(2.*dy);
	const double p_J_y0 = njets*R/M_PI;
	return min(p_J_y_large, p_J_y0, 1.);
	}

	int PhaseSpacePoint::sample_ng_jets(
	int ng, std::vector<fastjet::PseudoJet> const & Born_jets
	){
	const double p_J = probability_in_jet(Born_jets);
	std::binomial_distribution<> bin_dist(ng, p_J);
	const int ng_J = bin_dist(ran_.get());
	weight_ = std::pow(p_J, -ng_J)std::pow(1 - p_J, ng_J - ng);
	return ng_J;
	}

	std::vector<fastjet::PseudoJet> PhaseSpacePoint::reshuffle(
	std::vector<fastjet::PseudoJet> const & Born_jets,
	fastjet::PseudoJet const & q
	){
	if(q == fastjet::PseudoJet{0, 0, 0, 0}) return Born_jets;
	const auto jets = resummation_jet_momenta(Born_jets, q);
	if(jets.empty()){
	weight_ = 0;
	return {};
	}

	// additional Jacobian to ensure Born integration over delta gives 1
	weight_ *= resummation_jet_weight(Born_jets, q);
	return jets;
	}

	std::vector<int> PhaseSpacePoint::distribute_jet_partons(
	int ng_jets, std::vector<fastjet::PseudoJet> const & jets
	){
	size_t first_valid_jet = 0;
	size_t num_valid_jets = jets.size();
	const double R_eff = 5./3.*param_.jet_param.def.R();
	// if there is an unordered jet too far away from the FKL jets
	// then extra gluon constituents of the unordered jet would
	// violate the FKL rapidity ordering
	if((unob_\|\|qqxb_) && jets[0].delta_R(jets[1]) > R_eff){
	++first_valid_jet;
	--num_valid_jets;
	}
	else if((unof_\|\|qqxf_) && jets[jets.size()-1].delta_R(jets[jets.size()-2]) > R_eff){
	--num_valid_jets;
	}
	std::vector<int> np(jets.size(), 1);
	for(int i = 0; i < ng_jets; ++i){
	++np[first_valid_jet + ran_.get().flat() * num_valid_jets];
	}
	weight_ *= std::pow(num_valid_jets, ng_jets);
	return np;
	}

	#ifndef NDEBUG
	namespace{
	bool tagged_FKL_backward(
	std::vector<fastjet::PseudoJet> const & jet_partons
	){
	return std::find_if(
	begin(jet_partons), end(jet_partons),
	[](fastjet::PseudoJet const & p){
	return p.user_index() == backward_FKL_idx;
	}
	) != end(jet_partons);
	}

	bool tagged_FKL_forward(
	std::vector<fastjet::PseudoJet> const & jet_partons
	){
	// the most forward FKL parton is most likely near the end of jet_partons;
	// start search from there
	return std::find_if(
	jet_partons.rbegin(), jet_partons.rend(),
	[](fastjet::PseudoJet const & p){
	return p.user_index() == forward_FKL_idx;
	}
	) != jet_partons.rend();
	}

	bool tagged_FKL_extremal(
	std::vector<fastjet::PseudoJet> const & jet_partons
	){
	return tagged_FKL_backward(jet_partons) && tagged_FKL_forward(jet_partons);
	}

	} // namespace anonymous
	#endif

	std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
	std::vector<fastjet::PseudoJet> const & jets,
	int ng_jets
	){
	return split(jets, distribute_jet_partons(ng_jets, jets));
	}

	bool PhaseSpacePoint::pass_extremal_cuts(
	fastjet::PseudoJet const & ext_parton,
	fastjet::PseudoJet const & jet
	) const{
	if(ext_parton.pt() < param_.min_extparton_pt) return false;
	return (ext_parton - jet).pt()/jet.pt() < param_.max_ext_soft_pt_fraction;
	}

	std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
	std::vector<fastjet::PseudoJet> const & jets,
	std::vector<int> const & np
	){
	assert(! jets.empty());
	assert(jets.size() == np.size());
	assert(pass_resummation_cuts(jets));

	const size_t most_backward_FKL_idx = 0 + unob_ + qqxb_;
	const size_t most_forward_FKL_idx = jets.size() - 1 - unof_ - qqxf_;
	const auto & jet = param_.jet_param;
	const JetSplitter jet_splitter{jet.def, jet.min_pt, ran_};

	std::vector<fastjet::PseudoJet> jet_partons;
	// randomly distribute jet gluons among jets
	for(size_t i = 0; i < jets.size(); ++i){
	auto split_res = jet_splitter.split(jets[i], np[i]);
	weight_ *= split_res.weight;
	if(weight_ == 0) return {};
	assert(
	std::all_of(
	begin(split_res.constituents), end(split_res.constituents),
	is_jet_parton
	)
	);
	const auto first_new_parton = jet_partons.insert(
	end(jet_partons),
	begin(split_res.constituents), end(split_res.constituents)
	);
	// mark uno and extremal FKL emissions here so we can check
	// their position once all emissions are generated
	auto extremal = end(jet_partons);
	if (i == most_backward_FKL_idx){ //FKL backward emission
	extremal = std::min_element(
	first_new_parton, end(jet_partons), rapidity_less{}
	);
	extremal->set_user_index(backward_FKL_idx);
	}
	else if(((unob_ \|\| qqxb_) && i == 0)){
	// unordered/qqxb
	extremal = std::min_element(
	first_new_parton, end(jet_partons), rapidity_less{}
	);
	extremal->set_user_index((unob_)?unob_idx:qqxb_idx);
	}

	else if (i == most_forward_FKL_idx){
	extremal = std::max_element(
	first_new_parton, end(jet_partons), rapidity_less{}
	);
	extremal->set_user_index(forward_FKL_idx);
	}
	else if(((unof_ \|\| qqxf_) && i == jets.size() - 1)){
	// unordered/qqxf
	extremal = std::max_element(
	first_new_parton, end(jet_partons), rapidity_less{}
	);
	extremal->set_user_index((unof_)?unof_idx:qqxf_idx);
	}
	if(
	extremal != end(jet_partons)
	&& !pass_extremal_cuts(*extremal, jets[i])
	){
	weight_ = 0;
	return {};
	}
	}
	assert(tagged_FKL_extremal(jet_partons));
	std::sort(begin(jet_partons), end(jet_partons), rapidity_less{});
	if(
	!extremal_ok(jet_partons)
	\|\| !split_preserved_jets(jets, jet_partons)
	){
	weight_ = 0.;
	return {};
	}
	return jet_partons;
	}

	bool PhaseSpacePoint::extremal_ok(
	std::vector<fastjet::PseudoJet> const & partons
	) const{
	assert(std::is_sorted(begin(partons), end(partons), rapidity_less{}));
	if(unob_ && partons.front().user_index() != unob_idx) return false;
	if(unof_ && partons.back().user_index() != unof_idx) return false;
	if(qqxb_ && partons.front().user_index() != qqxb_idx) return false;
	if(qqxf_ && partons.back().user_index() != qqxf_idx) return false;
	return
	most_backward_FKL(partons).user_index() == backward_FKL_idx
	&& most_forward_FKL(partons).user_index() == forward_FKL_idx;
	}

	bool PhaseSpacePoint::split_preserved_jets(
	std::vector<fastjet::PseudoJet> const & jets,
	std::vector<fastjet::PseudoJet> const & jet_partons
	) const{
	assert(std::is_sorted(begin(jets), end(jets), rapidity_less{}));

	const auto split_jets = sorted_by_rapidity(cluster_jets(jet_partons));
	// this can happen if two overlapping jets
	// are both split into more than one parton
	if(split_jets.size() != jets.size()) return false;
	for(size_t i = 0; i < split_jets.size(); ++i){
	// this can happen if there are two overlapping jets
	// and a parton is assigned to the "wrong" jet
	if(!nearby_ep(jets[i].rapidity(), split_jets[i].rapidity(), 1e-2)){
	return false;
	}
	}
	return true;
	}

	template<class Particle>
	Particle const & PhaseSpacePoint::most_backward_FKL(
	std::vector<Particle> const & partons
	) const{
	return partons[0 + unob_ + qqxb_];
	}

	template<class Particle>
	Particle const & PhaseSpacePoint::most_forward_FKL(
	std::vector<Particle> const & partons
	) const{
	const size_t idx = partons.size() - 1 - unof_ - qqxf_;
	assert(idx < partons.size());
	return partons[idx];
	}

	template<class Particle>
	Particle & PhaseSpacePoint::most_backward_FKL(
	std::vector<Particle> & partons
	) const{
	return partons[0 + unob_ + qqxb_];
	}

	template<class Particle>
	Particle & PhaseSpacePoint::most_forward_FKL(
	std::vector<Particle> & partons
	) const{
	const size_t idx = partons.size() - 1 - unof_ - qqxf_;
	assert(idx < partons.size());
	return partons[idx];
	}

	namespace {
	bool contains_idx(
	fastjet::PseudoJet const & jet, fastjet::PseudoJet const & parton
	){
	auto const & constituents = jet.constituents();
	const int idx = parton.user_index();
	return std::find_if(
	begin(constituents), end(constituents),
	[idx](fastjet::PseudoJet const & con){return con.user_index() == idx;}
	) != end(constituents);
	}
	}

	/**
	* final jet test:
	* - number of jets must match Born kinematics
	* - no partons designated as nonjet may end up inside jets
	* - all other outgoing partons must end up inside jets
	* - the extremal (in rapidity) partons must be inside the extremal jets
	* - rapidities must be the same (by construction)
	*/
	bool PhaseSpacePoint::jets_ok(
	std::vector<fastjet::PseudoJet> const & Born_jets,
	std::vector<fastjet::PseudoJet> const & partons
	) const{
	fastjet::ClusterSequence cs(partons, param_.jet_param.def);
	const auto jets = sorted_by_rapidity(cs.inclusive_jets(param_.jet_param.min_pt));
	if(jets.size() != Born_jets.size()) return false;
	int in_jet = 0;
	for(size_t i = 0; i < jets.size(); ++i){
	assert(jets[i].has_constituents());
	for(auto && parton: jets[i].constituents()){
	if(is_nonjet_parton(parton)) return false;
	}
	in_jet += jets[i].constituents().size();
	}
	const int expect_in_jet = std::count_if(
	partons.cbegin(), partons.cend(), is_jet_parton
	);
	if(in_jet != expect_in_jet) return false;
	// note that PseudoJet::contains does not work here
	if(! (
	contains_idx(most_backward_FKL(jets), most_backward_FKL(partons))
	&& contains_idx(most_forward_FKL(jets), most_forward_FKL(partons))
	)) return false;
	if(unob_ && !contains_idx(jets.front(), partons.front())) return false;
	if(unof_ && !contains_idx(jets.back(), partons.back())) return false;
	for(size_t i = 0; i < jets.size(); ++i){
	assert(nearby_ep(jets[i].rapidity(), Born_jets[i].rapidity(), 1e-2));
	}
	return true;
	}

	void PhaseSpacePoint::reconstruct_incoming(
	std::array<Particle, 2> const & Born_incoming
	){
	std::tie(incoming_[0].p, incoming_[1].p) = incoming_momenta(outgoing_);
	for(size_t i = 0; i < incoming_.size(); ++i){
	incoming_[i].type = Born_incoming[i].type;
	}
	assert(momentum_conserved());
	}

	double PhaseSpacePoint::phase_space_normalisation(
	int num_Born_jets, int num_out_partons
	) const{
	return pow(16*pow(M_PI,3), num_Born_jets - num_out_partons);
	}

	bool PhaseSpacePoint::momentum_conserved() const{
	fastjet::PseudoJet diff;
	for(auto const & in: incoming()) diff += in.p;
	const double norm = diff.E();
	for(auto const & out: outgoing()) diff -= out.p;
	return nearby(diff, fastjet::PseudoJet{}, norm);
	}

	} //namespace HEJ

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