diff --git a/FixedOrderGen/src/EventGenerator.cc b/FixedOrderGen/src/EventGenerator.cc
index 52bb69b..935b1eb 100644
--- a/FixedOrderGen/src/EventGenerator.cc
+++ b/FixedOrderGen/src/EventGenerator.cc
@@ -1,101 +1,100 @@
 /**
  *  \authors   The HEJ collaboration (see AUTHORS for details)
  *  \date      2019-2020
  *  \copyright GPLv2 or later
  */
 #include "EventGenerator.hh"
 
 #include <cstddef>
 #include <utility>
 
 #include "HEJ/Config.hh"
 #include "HEJ/Event.hh"
 #include "HEJ/event_types.hh"
 #include "HEJ/EWConstants.hh"
 #include "HEJ/exceptions.hh"
 #include "HEJ/HiggsCouplingSettings.hh"
 
 #include "Process.hh"
 #include "Beam.hh"
 #include "JetParameters.hh"
 #include "PhaseSpacePoint.hh"
 
 namespace HEJFOG {
   EventGenerator::EventGenerator(
       Process process,
       Beam beam,
       HEJ::ScaleGenerator scale_gen,
       JetParameters jets,
       int pdf_id,
       double subl_chance,
       Subleading subl_channels,
       ParticlesDecayMap particle_decays,
       HEJ::HiggsCouplingSettings Higgs_coupling,
       HEJ::EWConstants ew_parameters,
       std::shared_ptr<HEJ::RNG> ran
   ):
     pdf_{pdf_id, beam.particles[0], beam.particles[1]},
     ME_{
       [this](double mu){ return pdf_.Halphas(mu); },
       HEJ::MatrixElementConfig{
         false,
         std::move(Higgs_coupling),
         ew_parameters
       }
     },
     scale_gen_{std::move(scale_gen)},
     process_{std::move(process)},
     jets_{std::move(jets)},
     beam_{std::move(beam)},
     subl_chance_{subl_chance},
     subl_channels_{subl_channels},
     particle_decays_{std::move(particle_decays)},
     ew_parameters_{ew_parameters},
     ran_{std::move(ran)}
   {
   }
 
   HEJ::optional<HEJ::Event> EventGenerator::gen_event(){
     HEJFOG::PhaseSpacePoint psp{
       process_,
       jets_,
       pdf_, beam_.energy,
       subl_chance_, subl_channels_,
       particle_decays_,
       ew_parameters_,
       *ran_
     };
     status_ = psp.status();
     if(status_ != Status::good) return {};
 
     HEJ::Event ev = scale_gen_(
         HEJ::Event{
           to_EventData( std::move(psp) ).cluster( jets_.def, jets_.min_pt)
         }
     );
     if(!is_resummable(ev.type())){
-      std::cerr << ev << std::endl;
       throw HEJ::not_implemented("Tried to generate a event type, "
         "which is not yet implemented in HEJ.");
     }
 
     ev.generate_colours(*ran_);
 
     const double shat = HEJ::shat(ev);
     const double xa = (ev.incoming()[0].E()-ev.incoming()[0].pz())/(2.*beam_.energy);
     const double xb = (ev.incoming()[1].E()+ev.incoming()[1].pz())/(2.*beam_.energy);
 
     // evaluate matrix element
     ev.parameters() *= ME_.tree(ev)/(shat*shat);
     // and PDFs
     ev.central().weight *= pdf_.pdfpt(0,xa,ev.central().muf, ev.incoming()[0].type);
     ev.central().weight *= pdf_.pdfpt(0,xb,ev.central().muf, ev.incoming()[1].type);
     for(std::size_t i = 0; i < ev.variations().size(); ++i){
       auto & var = ev.variations(i);
       var.weight *= pdf_.pdfpt(0,xa,var.muf, ev.incoming()[0].type);
       var.weight *= pdf_.pdfpt(0,xb,var.muf, ev.incoming()[1].type);
     }
     return ev;
   }
 
 }
diff --git a/FixedOrderGen/src/PhaseSpacePoint.cc b/FixedOrderGen/src/PhaseSpacePoint.cc
index 7097e35..83cbd74 100644
--- a/FixedOrderGen/src/PhaseSpacePoint.cc
+++ b/FixedOrderGen/src/PhaseSpacePoint.cc
@@ -1,937 +1,921 @@
 /**
  *  \authors   The HEJ collaboration (see AUTHORS for details)
  *  \date      2019-2020
  *  \copyright GPLv2 or later
  */
 #include "PhaseSpacePoint.hh"
 
 #include <algorithm>
 #include <cassert>
 #include <cmath>
 #include <cstdlib>
 #include <iostream>
 #include <iterator>
 #include <limits>
 #include <tuple>
 #include <type_traits>
 #include <utility>
 
 #include "fastjet/ClusterSequence.hh"
 
 #include "HEJ/Constants.hh"
 #include "HEJ/EWConstants.hh"
 #include "HEJ/exceptions.hh"
 #include "HEJ/kinematics.hh"
 #include "HEJ/Particle.hh"
 #include "HEJ/PDF.hh"
 #include "HEJ/RNG.hh"
 #include "HEJ/utility.hh"
 
 #include "JetParameters.hh"
 #include "Process.hh"
 
 namespace {
   using namespace HEJ;
   static_assert(
       std::numeric_limits<double>::has_quiet_NaN,
       "no quiet NaN for double"
   );
   constexpr double NaN = std::numeric_limits<double>::quiet_NaN();
 } // namespace anonymous
 
 namespace HEJFOG {
   Event::EventData to_EventData(PhaseSpacePoint psp){
   //! @TODO Same function already in HEJ
     Event::EventData result;
     result.incoming = std::move(psp).incoming_;
     assert(result.incoming.size() == 2);
     result.outgoing = std::move(psp).outgoing_;
     // technically Event::EventData doesn't have to be sorted,
     // but PhaseSpacePoint should be anyway
     assert(
         std::is_sorted(
             begin(result.outgoing), end(result.outgoing),
             rapidity_less{}
         )
     );
     assert(result.outgoing.size() >= 2);
     result.decays = std::move(psp).decays_;
     result.parameters.central = {NaN, NaN, psp.weight()};
     return result;
   }
 
   PhaseSpacePoint::ConstPartonIterator PhaseSpacePoint::begin_partons() const {
     return cbegin_partons();
   }
   PhaseSpacePoint::ConstPartonIterator PhaseSpacePoint::cbegin_partons() const {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(HEJ::Particle const &)>(HEJ::is_parton),
-        cbegin(outgoing()),
-        cend(outgoing())
-    );
+    return {HEJ::is_parton, cbegin(outgoing()), cend(outgoing())};
   }
 
   PhaseSpacePoint::ConstPartonIterator PhaseSpacePoint::end_partons() const {
     return cend_partons();
   }
   PhaseSpacePoint::ConstPartonIterator PhaseSpacePoint::cend_partons() const {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(HEJ::Particle const &)>(HEJ::is_parton),
-        cend(outgoing()),
-        cend(outgoing())
-    );
+    return {HEJ::is_parton, cend(outgoing()), cend(outgoing())};
   }
 
   PhaseSpacePoint::ConstReversePartonIterator PhaseSpacePoint::rbegin_partons() const {
     return crbegin_partons();
   }
   PhaseSpacePoint::ConstReversePartonIterator PhaseSpacePoint::crbegin_partons() const {
     return std::reverse_iterator<ConstPartonIterator>( cend_partons() );
   }
 
   PhaseSpacePoint::ConstReversePartonIterator PhaseSpacePoint::rend_partons() const {
     return crend_partons();
   }
   PhaseSpacePoint::ConstReversePartonIterator PhaseSpacePoint::crend_partons() const {
     return std::reverse_iterator<ConstPartonIterator>( cbegin_partons() );
   }
 
   PhaseSpacePoint::PartonIterator PhaseSpacePoint::begin_partons() {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(HEJ::Particle const &)>(HEJ::is_parton),
-        begin(outgoing_),
-        end(outgoing_)
-    );
+    return {HEJ::is_parton, begin(outgoing_), end(outgoing_)};
   }
 
   PhaseSpacePoint::PartonIterator PhaseSpacePoint::end_partons() {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(HEJ::Particle const &)>(HEJ::is_parton),
-        end(outgoing_),
-        end(outgoing_)
-    );
+    return {HEJ::is_parton, end(outgoing_), end(outgoing_)};
   }
 
   PhaseSpacePoint::ReversePartonIterator PhaseSpacePoint::rbegin_partons() {
     return std::reverse_iterator<PartonIterator>( end_partons() );
   }
 
   PhaseSpacePoint::ReversePartonIterator PhaseSpacePoint::rend_partons() {
     return std::reverse_iterator<PartonIterator>( begin_partons() );
   }
 
   namespace {
     bool can_swap_to_uno(
         Particle const & p1, Particle const & p2
     ){
       assert(is_parton(p1) && is_parton(p2));
       return p1.type != pid::gluon
           && p2.type == pid::gluon;
     }
 
     size_t count_gluons(PhaseSpacePoint::ConstPartonIterator first,
                         PhaseSpacePoint::ConstPartonIterator last
     ){
       return std::count_if(first, last, [](Particle const & p)
         {return p.type == pid::gluon;});
     }
 
     /** assumes FKL configurations between first and last,
      * else there can be a quark in a non-extreme position
      * e.g. uno configuration gqg would pass
      */
     Subleading possible_qqx(
       PhaseSpacePoint::ConstPartonIterator first,
       PhaseSpacePoint::ConstReversePartonIterator last
     ){
       using namespace subleading;
       assert( std::distance( first,last.base() )>2 );
       Subleading channels(~0l);
       channels.reset(eqqx);
       channels.reset(cqqx);
       auto const ngluon = count_gluons(first,last.base());
       if(ngluon < 2) return channels;
       if(first->type==pid::gluon || last->type==pid::gluon){
         channels.set(eqqx);
       }
       if(std::distance(first,last.base())>=4){
         channels.set(cqqx);
       }
       return channels;
     }
 
     bool is_AWZ_proccess(Process const & proc){
       return proc.boson && is_AWZ_boson(*proc.boson);
     }
 
     bool is_up_type(Particle const & part){
       return is_anyquark(part) && !(std::abs(part.type)%2);
     }
     bool is_down_type(Particle const & part){
       return is_anyquark(part) && std::abs(part.type)%2;
     }
     bool can_couple_to_W(Particle const & part, pid::ParticleID const W_id){
       const int W_charge = W_id>0?1:-1;
       return std::abs(part.type)<5
         && ( (W_charge*part.type > 0 && is_up_type(part))
           || (W_charge*part.type < 0 && is_down_type(part)) );
     }
   }
 
   void PhaseSpacePoint::maybe_turn_to_subl(
       double chance,
       Subleading channels,
       Process const & proc,
       RNG & ran
   ){
     if(proc.njets <= 2) return;
     assert(outgoing_.size() >= 2);
 
     // decide what kind of subleading process is allowed
     bool can_be_uno_backward = can_swap_to_uno(
       *cbegin_partons(), *(++cbegin_partons()) );
     bool can_be_uno_forward  = can_swap_to_uno(
       *crbegin_partons(), *(++crbegin_partons()) );
     // Special case: Higgs can not be outside of uno
     if(proc.boson && *proc.boson==pid::Higgs){
       if(outgoing_.begin()->type == pid::Higgs
           || (++outgoing_.begin())->type==pid::Higgs){
         can_be_uno_backward = false;
       }
       if(outgoing_.rbegin()->type == pid::Higgs
           || (++outgoing_.rbegin())->type==pid::Higgs){
         can_be_uno_forward = false;
       }
     }
     if(channels[subleading::uno]){
       channels.set(subleading::uno, can_be_uno_backward || can_be_uno_forward);
     }
     channels &= possible_qqx(cbegin_partons(), crbegin_partons());
 
     bool allow_strange = true;
     if(is_AWZ_proccess(proc)) {
       if(std::none_of(cbegin_partons(), cend_partons(),
           [&proc](Particle const & p){
             return can_couple_to_W(p, *proc.boson);})) {
         // enforce qqx if A/W/Z can't couple somewhere else
         // this is ensured to work through filter_partons in reconstruct_incoming
         channels.reset(subleading::uno);
         assert(channels.any());
         chance = 1.;
         // strange not allowed for W
         if(std::abs(*proc.boson)== pid::Wp) allow_strange = false;
       }
     }
 
     std::size_t const nchannels = channels.count();
     // no subleading
     if(nchannels==0) return;
     if(ran.flat() >= chance){
       weight_ /= 1 - chance;
       return;
     }
     weight_ /= chance;
 
     // select channel
     double const step = 1./nchannels;
     weight_*=nchannels;
     unsigned selected = subleading::first;
     double rnd = nchannels>1?ran.flat():0.;
     for(; selected<=subleading::last; ++selected){
       assert(rnd>=0);
       if(channels[selected]){
         if(rnd<step) break;
         rnd-=step;
       }
     }
     switch(selected){
       case subleading::uno:
         return turn_to_uno(can_be_uno_backward, can_be_uno_forward, ran);
       case subleading::cqqx:
         return turn_to_cqqx(allow_strange, ran);
       case subleading::eqqx:
         return turn_to_eqqx(allow_strange, ran);
       default:
         throw std::logic_error{"unreachable"};
     }
   }
 
   void PhaseSpacePoint::turn_to_uno(
       const bool can_be_uno_backward, const bool can_be_uno_forward,
       RNG & ran
   ){
     if(!can_be_uno_backward && !can_be_uno_forward) return;
     if(can_be_uno_backward && can_be_uno_forward){
       weight_ *= 2.;
       if(ran.flat() < 0.5){
         return std::swap(begin_partons()->type, (++begin_partons())->type);
       }
       return std::swap(rbegin_partons()->type, (++rbegin_partons())->type);
     }
     if(can_be_uno_backward){
       return std::swap(begin_partons()->type, (++begin_partons())->type);
     }
     assert(can_be_uno_forward);
     std::swap(rbegin_partons()->type, (++rbegin_partons())->type);
   }
 
   //! select flavour of quark
   int PhaseSpacePoint::select_qqx_flavour(const bool allow_strange, RNG & ran){
     const double r1 = 2.*ran.flat()-1.;
     const double max_flavour = allow_strange?N_F:N_F-1;
     weight_ *= max_flavour*2;
     int flavour = pid::down + std::floor(std::abs(r1)*max_flavour);
     return flavour*(r1<0.?-1:1);
   }
 
   void PhaseSpacePoint::turn_to_cqqx(const bool allow_strange, RNG & ran){
     // we assume all FKL partons to be gluons
     auto first = ++begin_partons();
     auto last  = ++rbegin_partons();
     auto const ng = std::distance(first, last.base());
     if(ng < 2)
       throw std::logic_error("not enough gluons to create qqx");
     int flavour = select_qqx_flavour(allow_strange, ran);
     // select gluon for switch
     if(ng!=2){
       const double steps = 1./(ng-1);
       weight_ /= steps;
       for(auto rnd = ran.flat(); rnd>steps; ++first){
         rnd-=steps;
       }
     }
     first->type = static_cast<ParticleID>(flavour);
     (++first)->type = static_cast<ParticleID>(-flavour);
   }
 
   void PhaseSpacePoint::turn_to_eqqx(const bool allow_strange, RNG & ran){
     /// find first and last gluon in FKL chain
     auto first  = begin_partons();
     const bool can_forward = !is_anyquark(*first);
     auto last = rbegin_partons();
     const bool can_backward = !is_anyquark(*last);
     if(std::distance(first, last.base()) < 2)
       throw std::logic_error("not enough gluons to create qqx");
     int flavour = select_qqx_flavour(allow_strange, ran);
     // select gluon for switch
     if(can_forward && !can_backward){
       first->type = static_cast<ParticleID>(flavour);
       (++first)->type = static_cast<ParticleID>(-flavour);
       return;
     }
     if(!can_forward && can_backward){
       last->type = static_cast<ParticleID>(flavour);
       (++last)->type = static_cast<ParticleID>(-flavour);
       return;
     }
     assert(can_forward && can_backward);
     weight_*=2.;
     if(ran.flat()>0.5){
       first->type = static_cast<ParticleID>(flavour);
       (++first)->type = static_cast<ParticleID>(-flavour);
       return;
     }
     last->type = static_cast<ParticleID>(flavour);
     (++last)->type = static_cast<ParticleID>(-flavour);
   }
 
   template<class ParticleMomenta>
   fastjet::PseudoJet PhaseSpacePoint::gen_last_momentum(
       ParticleMomenta const & other_momenta,
       const double mass_square, const double y
   ) const {
     std::array<double,2> pt{0.,0.};
     for (auto const & p: other_momenta) {
       pt[0]-= p.px();
       pt[1]-= p.py();
     }
 
     const double mperp = std::sqrt(pt[0]*pt[0]+pt[1]*pt[1]+mass_square);
     const double pz=mperp*std::sinh(y);
     const double E=mperp*std::cosh(y);
 
     return {pt[0], pt[1], pz, E};
   }
 
   namespace {
     //! adds a particle to target (in correct rapidity ordering)
     //! @returns    positon of insertion
     auto insert_particle(std::vector<Particle> & target,
       Particle && particle
     ){
       const auto pos = std::upper_bound(
           begin(target),end(target),particle,rapidity_less{}
       );
       target.insert(pos, std::move(particle));
       return pos;
     }
   }
 
   PhaseSpacePoint::PhaseSpacePoint(
     Process const & proc,
     JetParameters const & jet_param,
     PDF & pdf, double E_beam,
     double const subl_chance,
     Subleading subl_channels,
     ParticlesDecayMap const & particle_decays,
     EWConstants const & ew_parameters,
     RNG & ran
   ){
     assert(proc.njets >= 2);
     status_ = Status::good;
     weight_ = 1;
 
     // ensure that all setting are consistent
     if(subl_chance == 0.)
       subl_channels.reset();
 
     const int nout = proc.njets + (proc.boson?1:0) + proc.boson_decay.size();
     outgoing_.reserve(nout);
 
     // generate parton momenta
     const bool is_pure_jets = (nout == proc.njets);
     auto partons = gen_LO_partons(
         proc.njets, is_pure_jets, jet_param, E_beam, ran
     );
     // pre fill flavour with gluons
     for(auto&& p_out: partons) {
       outgoing_.emplace_back(Particle{pid::gluon, std::move(p_out), {}});
     }
     if(status_ != Status::good) return;
 
     if(proc.boson){ // decay boson
       auto const & boson_prop = ew_parameters.prop(*proc.boson) ;
       auto boson{ gen_boson(*proc.boson, boson_prop.mass, boson_prop.width, ran) };
       const auto pos{insert_particle(outgoing_, std::move(boson))};
       const size_t boson_idx = std::distance(begin(outgoing_), pos);
       auto const & boson_decay = particle_decays.find(*proc.boson);
       if( !proc.boson_decay.empty() ){ // decay given in proc
         decays_.emplace(
             boson_idx,
             decay_boson(outgoing_[boson_idx], proc.boson_decay, ran)
         );
       } else if( boson_decay != particle_decays.end()
                 && !boson_decay->second.empty() ){ // decay given explicitly
         decays_.emplace(
             boson_idx,
             decay_boson(outgoing_[boson_idx], boson_decay->second, ran)
         );
       }
     }
     // normalisation of momentum-conserving delta function
     weight_ *= std::pow(2*M_PI, 4);
 
     /** @TODO
      *  uf (jet_param.min_pt) doesn't correspond to our final scale choice.
      *  The HEJ scale generators currently expect a full event as input,
      *  so fixing this is not completely trivial
      */
     reconstruct_incoming(proc, subl_chance, subl_channels, pdf, E_beam, jet_param.min_pt, ran);
     if(status_ != Status::good) return;
     // set outgoing states
     begin_partons()->type = incoming_[0].type;
     rbegin_partons()->type = incoming_[1].type;
 
     maybe_turn_to_subl(subl_chance, subl_channels, proc, ran);
 
     if(proc.boson) couple_boson(*proc.boson, ran);
   }
 
   // pt generation, see eq:pt_sampling in developer manual
   double PhaseSpacePoint::gen_hard_pt(
     const int np , const double ptmin, const double ptmax, const double /* y */,
     RNG & ran
   ) {
     // heuristic parameter for pt sampling, see eq:pt_par in developer manual
     const double ptpar = ptmin + np/5.;
 
     const double arctan = std::atan((ptmax - ptmin)/ptpar);
     const double xpt = ran.flat();
     const double pt = ptmin + ptpar*std::tan(xpt*arctan);
     const double cosine = std::cos(xpt*arctan);
     weight_ *= pt*ptpar*arctan/(cosine*cosine);
     return pt;
   }
 
   double PhaseSpacePoint::gen_soft_pt(int np, double max_pt, RNG & ran) {
     constexpr double ptpar = 4.;
 
     const double r = ran.flat();
     const double pt = max_pt + ptpar/np*std::log(r);
     weight_ *= pt*ptpar/(np*r);
     return pt;
   }
 
   double PhaseSpacePoint::gen_parton_pt(
       int count, JetParameters const & jet_param, double max_pt, double y,
       RNG & ran
   ) {
     constexpr double p_small_pt = 0.02;
 
     if(! jet_param.peak_pt) {
        return gen_hard_pt(count, jet_param.min_pt, max_pt, y, ran);
     }
     const double r = ran.flat();
     if(r > p_small_pt) {
       weight_ /= 1. - p_small_pt;
       return gen_hard_pt(count, *jet_param.peak_pt, max_pt, y, ran);
     }
     weight_ /= p_small_pt;
     const double pt =  gen_soft_pt(count, *jet_param.peak_pt, ran);
     if(pt < jet_param.min_pt) {
       weight_=0.0;
       status_ = Status::not_enough_jets;
       return jet_param.min_pt;
     }
     return pt;
   }
 
   std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_LO_partons(
       int np, bool is_pure_jets,
       JetParameters const & jet_param,
       double max_pt,
       RNG & ran
   ){
     if (np<2) throw std::invalid_argument{"Not enough partons in gen_LO_partons"};
 
     weight_ /= std::pow(16.*std::pow(M_PI,3),np);
     weight_ /= std::tgamma(np+1); //remove rapidity ordering
     std::vector<fastjet::PseudoJet> partons;
     partons.reserve(np);
     for(int i = 0; i < np; ++i){
       const double y = -jet_param.max_y + 2*jet_param.max_y*ran.flat();
       weight_ *= 2*jet_param.max_y;
 
       const bool is_last_parton = i+1 == np;
       if(is_pure_jets && is_last_parton) {
         constexpr double parton_mass_sq = 0.;
         partons.emplace_back(gen_last_momentum(partons, parton_mass_sq, y));
         break;
       }
 
       const double phi = 2*M_PI*ran.flat();
       weight_ *= 2.0*M_PI;
 
       const double pt = gen_parton_pt(np, jet_param, max_pt, y, ran);
       if(weight_ == 0.0) return {};
 
       partons.emplace_back(fastjet::PtYPhiM(pt, y, phi));
       assert(jet_param.min_pt <= partons[i].pt());
       assert(partons[i].pt() <= max_pt+1e-5);
     }
     // Need to check that at LO, the number of jets = number of partons;
     fastjet::ClusterSequence cs(partons, jet_param.def);
     auto cluster_jets=cs.inclusive_jets(jet_param.min_pt);
     if (cluster_jets.size()!=unsigned(np)){
       weight_=0.0;
       status_ = Status::not_enough_jets;
       return {};
     }
 
     std::sort(begin(partons), end(partons), rapidity_less{});
 
     return partons;
   }
 
   Particle PhaseSpacePoint::gen_boson(
       ParticleID bosonid, double mass, double width,
       RNG & ran
   ){
     // Usual phase space measure
     weight_ /= 16.*std::pow(M_PI, 3);
 
     // Generate a y Gaussian distributed around 0
     /// @TODO check magic numbers for different boson Higgs
     /// @TODO better sampling for W
     const double stddev_y = 1.6;
     const double y = random_normal(stddev_y, ran);
     const double r1 = ran.flat();
     const double s_boson = mass*(
         mass + width*std::tan(M_PI/2.*r1 + (r1-1.)*std::atan(mass/width))
     );
     // off-shell s_boson sampling, compensates for Breit-Wigner
     /// @TODO use a flag instead
     if(std::abs(bosonid) == pid::Wp){
       weight_/=M_PI*M_PI*16.;  //Corrects B-W factors, see git issue 132
       weight_*= mass*width*( M_PI+2.*std::atan(mass/width) )
               / ( 1. + std::cos( M_PI*r1 + 2.*(r1-1.)*std::atan(mass/width) ) );
     }
 
     auto p = gen_last_momentum(outgoing_, s_boson, y);
 
     return Particle{bosonid, std::move(p), {}};
   }
 
   namespace {
     /// partons are ordered: even = anti, 0 = gluon
     ParticleID index_to_pid(size_t i){
       if(!i) return pid::gluon;
       return static_cast<ParticleID>( i%2 ? (i+1)/2 : -i/2 );
     }
 
     /// partons are ordered: even = anti, 0 = gluon
     size_t pid_to_index(ParticleID id){
       if(id==pid::gluon) return 0;
       return id>0 ? id*2-1 : std::abs(id)*2;
     }
 
     using part_mask = std::bitset<11>; //!< Selection mask for partons
 
     part_mask init_allowed(ParticleID const id){
       if(std::abs(id) == pid::proton)
         return ~0;
       part_mask out{0};
       if(is_parton(id))
         out[pid_to_index(id)] = 1;
       return out;
     }
 
     /// decides which "index" (see index_to_pid) are allowed for process
     part_mask allowed_quarks(ParticleID const boson){
       if(std::abs(boson) != pid::Wp){
         return ~1; // not a gluon
       }
       // special case W:
       // Wp: anti-down or up-type quark, no b/t
       // Wm: down or anti-up-type quark, no b/t
       return boson>0?0b00011001100
                     :0b00100110010;
     }
   }
 
   /**
    * @brief Returns list of all allowed initial states partons
    *
    * checks which partons are allowed as initial state:
    * 1. only allow what is given in the Runcard (p -> all)
    * 2. A/W/Z require something to couple to
    *  a) no qqx => no incoming gluon
    *  b) 2j     => no incoming gluon
    *  c) >3j    => can couple OR is gluon => 2 gluons become qqx later
    * 3. pure eqqx requires at least one gluon
    * 4. pure uno requires at least one quark
    */
   std::array<part_mask,2> PhaseSpacePoint::filter_partons(
       Process const & proc,
       double const subl_chance, Subleading const subl_channels,
       RNG & ran
   ){
     // all possible incoming states
     std::array<part_mask,2> allowed_partons{
         init_allowed(proc.incoming[0]),
         init_allowed(proc.incoming[1])
       };
     // special case A/W/Z
     if(proc.boson){
       auto couple_parton = allowed_quarks(*proc.boson);
       if(is_AWZ_proccess(proc)
           // coupling possible through input
           && allowed_partons[0] != (couple_parton&allowed_partons[0])
           && allowed_partons[1] != (couple_parton&allowed_partons[1])
           // qqx not possible
           && (proc.njets < 4
             ||  (!subl_channels[subleading::eqqx]
               && !subl_channels[subleading::cqqx])
           )
       ){
         // eqqx only possible if one incoming is a gluon
         if(proc.njets >= 3 && subl_channels[subleading::eqqx]){
           couple_parton.set(pid_to_index(HEJ::ParticleID::gluon));
         }
         if( (allowed_partons[0]&couple_parton).any()
           &&(allowed_partons[1]&couple_parton).none()
         ){
           allowed_partons[0]&=couple_parton;
         } else if( (allowed_partons[0]&couple_parton).none()
                 && (allowed_partons[1]&couple_parton).any()
         ){
           allowed_partons[1]&=couple_parton;
         } else if( (allowed_partons[0]&couple_parton).any()
                 && (allowed_partons[1]&couple_parton).any()
         ){
           double rnd = ran.flat();
           weight_*=3.;
           if(rnd<1./3.){
             allowed_partons[0] &= couple_parton;
             allowed_partons[1] &= ~couple_parton;
           } else if(rnd<2./3.){
             allowed_partons[0] &= ~couple_parton;
             allowed_partons[1] &= couple_parton;
           } else {
             allowed_partons[0] &= couple_parton;
             allowed_partons[1] &= couple_parton;
           }
         } else {
           throw std::invalid_argument{"Incoming state not allowed."};
         }
       }
     }
     // special case: pure subleading
     if(subl_chance!=1.){
       return allowed_partons;
     }
     auto other_channels = subl_channels;
     // pure eqqx
     other_channels.reset(subleading::eqqx);
     if(other_channels.none()){
       auto const gluon_idx = pid_to_index(pid::gluon);
       auto & first_beam = allowed_partons[0];
       auto & second_beam = allowed_partons[1];
       if(first_beam[gluon_idx] && !second_beam[gluon_idx]){
         first_beam.reset();
         first_beam.set(gluon_idx);
         return allowed_partons;
       }
       if(!first_beam[gluon_idx] && second_beam[gluon_idx]) {
         second_beam.reset();
         second_beam.set(gluon_idx);
         return allowed_partons;
       }
       if(first_beam[gluon_idx] && second_beam[gluon_idx]) {
         // both beams can be gluons
         // if one can't be a quark everything is good
         auto first_quarks = first_beam;
         first_quarks.reset(gluon_idx);
         auto second_quarks = second_beam;
         second_quarks.reset(gluon_idx);
         if(first_quarks.none() || second_quarks.none()){
           return allowed_partons;
         }
         // else choose one to be a gluon
         double rnd = ran.flat();
         weight_*=3.;
         if(rnd<1./3.){
           allowed_partons[0].reset();
           allowed_partons[0].set(gluon_idx);
           allowed_partons[1].reset(gluon_idx);
         } else if(rnd<2./3.){
           allowed_partons[1].reset();
           allowed_partons[1].set(gluon_idx);
           allowed_partons[0].reset(gluon_idx);
         } else {
           allowed_partons[0].reset();
           allowed_partons[0].set(gluon_idx);
           allowed_partons[1].reset();
           allowed_partons[1].set(gluon_idx);
         }
         return allowed_partons;
       }
       throw std::invalid_argument{
         "Incoming state not allowed for pure central qqx."};
     }
     other_channels = subl_channels;
     // pure uno
     other_channels.reset(subleading::uno);
     if(other_channels.none()){
       auto const gluon_idx = pid_to_index(pid::gluon);
       auto & first_beam = allowed_partons[0];
       auto first_quarks = first_beam;
       first_quarks.reset(gluon_idx);
       auto & second_beam = allowed_partons[1];
       auto second_quarks = second_beam;
       second_quarks.reset(gluon_idx);
       if(first_quarks.any() && second_quarks.none()){
         first_beam.reset(gluon_idx);
         return allowed_partons;
       }
       if(first_quarks.none() && second_quarks.any()) {
         second_beam.reset(gluon_idx);
         return allowed_partons;
       }
        if(first_quarks.any() && second_quarks.any()) {
         // both beams can be quarks
         // if one can't be gluon everything is good
         if(!first_beam[gluon_idx] || !second_beam[gluon_idx]){
           return allowed_partons;
         }
         // else choose one to be a quark
         double rnd = ran.flat();
         weight_*=3.;
         if(rnd<1./3.){
           allowed_partons[0].reset(gluon_idx);
           allowed_partons[1].reset();
           allowed_partons[1].set(gluon_idx);
         } else if(rnd<2./3.){
           allowed_partons[1].reset(gluon_idx);
           allowed_partons[0].reset();
           allowed_partons[0].set(gluon_idx);
         } else {
           allowed_partons[0].reset(gluon_idx);
           allowed_partons[1].reset(gluon_idx);
         }
         return allowed_partons;
       }
       throw std::invalid_argument{
         "Incoming state not allowed for pure unordered."};
     }
     return allowed_partons;
   }
 
 
   void PhaseSpacePoint::reconstruct_incoming(
       Process const & proc,
       double const subl_chance, Subleading const subl_channels,
       PDF & pdf, double E_beam,
       double uf,
       RNG & ran
   ){
     std::tie(incoming_[0].p, incoming_[1].p) = incoming_momenta(outgoing_);
     // calculate xa, xb
     const double sqrts=2*E_beam;
     const double xa=(incoming_[0].E()-incoming_[0].pz())/sqrts;
     const double xb=(incoming_[1].E()+incoming_[1].pz())/sqrts;
     // abort if phase space point is outside of collider energy reach
     if (xa>1. || xb>1.){
       weight_=0;
       status_ = Status::too_much_energy;
       return;
     }
     auto const & ids = proc.incoming;
     std::array<part_mask,2> allowed_partons
       = filter_partons(proc, subl_chance, subl_channels, ran);
     for(size_t i = 0; i < 2; ++i){
       if(ids[i] == pid::proton || ids[i] == pid::p_bar){
       // pick ids according to pdfs
         incoming_[i].type =
           generate_incoming_id(i, i?xb:xa, uf, pdf, allowed_partons[i], ran);
       } else {
         assert(allowed_partons[i][pid_to_index(ids[i])]);
         incoming_[i].type = ids[i];
       }
     }
     assert(momentum_conserved(1e-7));
   }
 
   ParticleID PhaseSpacePoint::generate_incoming_id(
       size_t const beam_idx, double const x, double const uf,
       PDF & pdf, part_mask allowed_partons, RNG & ran
   ){
     std::array<double,11> pdf_wt;
     pdf_wt[0] = allowed_partons[0]?
       std::fabs(pdf.pdfpt(beam_idx,x,uf,pid::gluon)):0.;
     double pdftot = pdf_wt[0];
     for(size_t i = 1; i < pdf_wt.size(); ++i){
       pdf_wt[i] = allowed_partons[i]?
         4./9.*std::fabs(pdf.pdfpt(beam_idx,x,uf,index_to_pid(i))):0;
       pdftot += pdf_wt[i];
     }
     const double r1 = pdftot * ran.flat();
     double sum = 0;
     for(size_t i=0; i < pdf_wt.size(); ++i){
       if (r1 < (sum+=pdf_wt[i])){
         weight_*= pdftot/pdf_wt[i];
         return index_to_pid(i);
       }
     }
     std::cerr << "Error in choosing incoming parton: "<<x<<" "<<uf<<" "
       <<sum<<" "<<pdftot<<" "<<r1<<std::endl;
     throw std::logic_error{"Failed to choose parton flavour"};
   }
 
   void PhaseSpacePoint::couple_boson(
     ParticleID const boson, RNG & ran
   ){
     if(std::abs(boson) != pid::Wp) return; // only matters for W
     /// @TODO this could be use to sanity check gamma and Z
 
     // find all possible quarks
     std::vector<PartonIterator> allowed_parts;
     for(auto part_it=begin_partons(); part_it!=end_partons(); ++part_it){
       // Wp -> up OR anti-down, Wm -> anti-up OR down, no bottom
       if ( can_couple_to_W(*part_it, boson) )
         allowed_parts.push_back(part_it);
     }
     if(allowed_parts.size() == 0){
       throw std::logic_error{"Found no parton for coupling with boson"};
     }
 
     // select one and flip it
     size_t idx = 0;
     if(allowed_parts.size() > 1){
       /// @TODO more efficient sampling
       ///       old code: probability[i] = exp(parton[i].y - W.y)
       idx = std::floor(ran.flat()*allowed_parts.size());
       weight_ *= allowed_parts.size();
     }
     const int W_charge = boson>0?1:-1;
     allowed_parts[idx]->type =
       static_cast<ParticleID>( allowed_parts[idx]->type - W_charge );
   }
 
   double PhaseSpacePoint::random_normal(
       double stddev,
       RNG & ran
   ){
     const double r1 = ran.flat();
     const double r2 = ran.flat();
     const double lninvr1 = -std::log(r1);
     const double result = stddev*std::sqrt(2.*lninvr1)*std::cos(2.*M_PI*r2);
     weight_ *= exp(result*result/(2*stddev*stddev))*std::sqrt(2.*M_PI)*stddev;
     return result;
   }
 
   bool PhaseSpacePoint::momentum_conserved(double ep) const{
     fastjet::PseudoJet diff;
     for(auto const & in: incoming()) diff += in.p;
     for(auto const & out: outgoing()) diff -= out.p;
     return nearby_ep(diff, fastjet::PseudoJet{}, ep);
   }
 
   Decay PhaseSpacePoint::select_decay_channel(
       std::vector<Decay> const & decays,
       RNG & ran
   ){
     double br_total = 0.;
     for(auto const & decay: decays) br_total += decay.branching_ratio;
     // adjust weight
     // this is given by (channel branching ratio)/(chance to pick channel)
     // where (chance to pick channel) =
     //       (channel branching ratio)/(total branching ratio)
     weight_ *= br_total;
     if(decays.size()==1) return decays.front();
     const double r1 = br_total*ran.flat();
     double br_sum = 0.;
     for(auto const & decay: decays){
       br_sum += decay.branching_ratio;
       if(r1 < br_sum) return decay;
     }
     throw std::logic_error{"unreachable"};
   }
 
   std::vector<Particle> PhaseSpacePoint::decay_boson(
       Particle const & parent,
       std::vector<Decay> const & decays,
       RNG & ran
   ){
     const auto channel = select_decay_channel(decays, ran);
     return decay_boson(parent, channel.products, ran);
   }
 
   std::vector<Particle> PhaseSpacePoint::decay_boson(
       Particle const & parent,
       std::vector<ParticleID> const & decays,
       RNG & ran
   ){
     if(decays.size() != 2){
       throw not_implemented{
         "only decays into two particles are implemented"
       };
     }
     std::vector<Particle> decay_products(decays.size());
     for(size_t i = 0; i < decays.size(); ++i){
       decay_products[i].type = decays[i];
     }
     // choose polar and azimuth angle in parent rest frame
     const double E = parent.m()/2;
     const double theta = 2.*M_PI*ran.flat();
     const double cos_phi = 2.*ran.flat()-1.;   // Jacobian Factors for W in line 418
     const double sin_phi = std::sqrt(1. - cos_phi*cos_phi);  // Know 0 < phi < pi
     const double px = E*std::cos(theta)*sin_phi;
     const double py = E*std::sin(theta)*sin_phi;
     const double pz = E*cos_phi;
     decay_products[0].p.reset(px, py, pz, E);
     decay_products[1].p.reset(-px, -py, -pz, E);
     for(auto & particle: decay_products) particle.p.boost(parent.p);
     return decay_products;
   }
 }
diff --git a/src/Event.cc b/src/Event.cc
index ba02818..20d3e38 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -1,1179 +1,1163 @@
 /**
  *  \authors   The HEJ collaboration (see AUTHORS for details)
  *  \date      2019-2020
  *  \copyright GPLv2 or later
  */
 #include "HEJ/Event.hh"
 
 #include <algorithm>
 #include <cassert>
 #include <cstdlib>
 #include <iomanip>
 #include <iterator>
 #include <memory>
 #include <numeric>
 #include <ostream>
 #include <string>
 #include <utility>
 
 #include "fastjet/ClusterSequence.hh"
 #include "fastjet/JetDefinition.hh"
 #include "fastjet/PseudoJet.hh"
 
 #include "LHEF/LHEF.h"
 
 #include "HEJ/Constants.hh"
 #include "HEJ/PDG_codes.hh"
 #include "HEJ/RNG.hh"
 #include "HEJ/exceptions.hh"
 #include "HEJ/optional.hh"
 
 namespace HEJ {
 
   namespace {
     using std::size_t;
 
     //! LHE status codes
     namespace lhe_status {
       enum Status: int {
         in = -1,
         decay = 2,
         out = 1,
       };
     }
     using LHE_Status = lhe_status::Status;
 
     //! true if leptonic W decay
     bool valid_W_decay( int const w_type, // sign of W
                         std::vector<Particle> const & decays
     ){
       if(decays.size() != 2) // no 1->2 decay
         return false;
       const int pidsum = decays[0].type + decays[1].type;
       if( std::abs(pidsum) != 1 || pidsum != w_type ) // correct charge
         return false;
       // leptonic decay (only check first, second follows from pidsum)
       if( w_type == 1 ) // W+
         return is_antilepton(decays[0]) || is_neutrino(decays[0]);
       // W-
       return is_lepton(decays[0]) || is_antineutrino(decays[0]);
     }
 
     //! true for Z decay to charged leptons
     bool valid_Z_decay(std::vector<Particle> const & decays){
       if(decays.size() != 2) // no 1->2 decay
         return false;
       const int pidsum = decays[0].type + decays[1].type;
       if( std::abs(pidsum) != 0 ) // correct charge
         return false;
       // leptonic decay (only check first, second follows from pidsum)
       return is_anylepton(decays[0]) && !is_anyneutrino(decays[0]);
     }
 
     /// @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(Event const & ev){
       std::vector<Particle> const & outgoing = ev.outgoing();
       if(ev.decays().size() > 1) // at most one decay
         return false;
       bool has_AWZH_boson = false;
       for( size_t i=0; i<outgoing.size(); ++i ){
         auto const & out{ outgoing[i] };
         if(is_AWZH_boson(out.type)){
           // at most one boson
           if(has_AWZH_boson) return false;
           has_AWZH_boson = true;
 
           // valid decay for W
           if(std::abs(out.type) == ParticleID::Wp){
             // exactly 1 decay of W
             if( ev.decays().size() != 1 || ev.decays().cbegin()->first != i )
               return false;
             if( !valid_W_decay(out.type>0?+1:-1, ev.decays().cbegin()->second) )
               return false;
           }
 
           // valid decay for Z
           if(out.type == ParticleID::Z_photon_mix){
             // exactly 1 decay
             if( ev.decays().size() != 1 || ev.decays().cbegin()->first != i )
               return false;
             if( !valid_Z_decay(ev.decays().cbegin()->second) )
               return false;
           }
         }
         else if(! is_parton(out.type)) return false;
       }
       return true;
     }
 
     /**
      * returns all EventTypes implemented in HEJ
      */
     size_t implemented_types(std::vector<Particle> const & bosons){
       using namespace event_type;
       if(bosons.empty()) return FKL | unob | unof | qqxexb | qqxexf | qqxmid;
       if(bosons.size()>1) return non_resummable; // multi boson
       switch (bosons[0].type) {
         case ParticleID::Wp:
         case ParticleID::Wm:
           return FKL | unob | unof | qqxexb | qqxexf | qqxmid;
         case ParticleID::Z_photon_mix:
           return FKL | unob | unof;
         case ParticleID::h:
           return FKL | unob | unof;
         default:
           return non_resummable;
       }
     }
 
     /**
      * \brief function which determines if type change is consistent with Wp emission.
      * @param in                      incoming Particle id
      * @param out                     outgoing Particle id
      * @param qqx                     Current both incoming/both outgoing?
      *
      * \see is_Wm_Change
      */
     bool is_Wp_Change(ParticleID in, ParticleID out, bool qqx){
       if(!qqx && (in==-1 || in== 2 || in==-3 || in== 4)) return out== (in-1);
       if( qqx && (in== 1 || in==-2 || in== 3 || in==-4)) return out==-(in+1);
       return false;
     }
 
     /**
      * \brief function which determines if type change is consistent with Wm emission.
      * @param in                      incoming Particle id
      * @param out                     outgoing Particle id
      * @param qqx                     Current both incoming/both outgoing?
      *
      * Ensures that change type of quark line is possible by a flavour changing
      * Wm emission. Allows checking of qqx currents also.
      */
     bool is_Wm_Change(ParticleID in, ParticleID out, bool qqx){
       if(!qqx && (in== 1 || in==-2 || in== 3 || in==-4)) return out== (in+1);
       if( qqx && (in==-1 || in== 2 || in==-3 || in== 4)) return out==-(in-1);
       return false;
     }
 
     /**
      * \brief checks if particle type remains same from incoming to outgoing
      * @param in                      incoming Particle
      * @param out                     outgoing Particle
      * @param qqx                     Current both incoming/outgoing?
      */
     bool no_flavour_change(ParticleID in, ParticleID out, bool qqx){
       const int qqxCurrent = qqx?-1:1;
       if(std::abs(in)<=pid::top || in==pid::gluon)
         return (in==out*qqxCurrent);
       return false;
     }
 
     bool has_2_jets(Event const & event){
       return event.jets().size() >= 2;
     }
 
     /**
      * \brief check if we have a valid Impact factor
      * @param in                      incoming Particle
      * @param out                     outgoing Particle
      * @param qqx                     Current both incoming/outgoing?
      * @param W_change                returns +1 if Wp, -1 if Wm, else 0
      */
     bool is_valid_impact_factor(
       ParticleID in, ParticleID out, bool qqx, int & W_change
     ){
       if( no_flavour_change(in, out, qqx) ){
         return true;
       }
       if( is_Wp_Change(in, out, qqx) ) {
         W_change+=1;
         return true;
       }
       if( is_Wm_Change(in, out, qqx) ) {
         W_change-=1;
         return true;
       }
       return false;
     }
 
     //! Returns all possible classifications from the impact factors
     // the beginning points are changed s.t. after the the classification they
     // point to the beginning of the (potential) FKL chain
     // sets W_change: + if Wp change
     //                0 if no change
     //                - if Wm change
     // This function can be used with forward & backwards iterators
     template<class OutIterator>
     size_t possible_impact_factors(
       ParticleID incoming_id,                                   // incoming
       OutIterator   & begin_out, OutIterator   const & end_out, // outgoing
       int & W_change, std::vector<Particle> const & boson,
       bool const backward                                       // backward?
     ){
       using namespace event_type;
       assert(boson.size() < 2);
       // keep track of all states that we don't test
       size_t not_tested = qqxmid;
       if(backward)
         not_tested |= unof | qqxexf;
       else
         not_tested |= unob | qqxexb;
 
       // Is this LL current?
       if( is_valid_impact_factor(incoming_id, begin_out->type, false, W_change) ){
         ++begin_out;
         return not_tested | FKL;
       }
 
       // or NLL current?
       // -> needs two partons in two different jets
       if( std::distance(begin_out, end_out)>=2
       ){
         auto next = std::next(begin_out);
         // Is this unordered emisson?
         if( incoming_id!=pid::gluon && begin_out->type==pid::gluon ){
           if( is_valid_impact_factor(
                 incoming_id, next->type, false, W_change )
           ){
             // veto Higgs inside uno
             assert(next!=end_out);
             if( !boson.empty() && boson.front().type == ParticleID::h
             ){
               if(  (backward && boson.front().rapidity() < next->rapidity())
                 ||(!backward && boson.front().rapidity() > next->rapidity()))
               return non_resummable;
             }
             begin_out = std::next(next);
             return not_tested | (backward?unob:unof);
           }
         }
         // Is this QQbar?
         else if( incoming_id==pid::gluon ){
           if( is_valid_impact_factor(
                 begin_out->type, next->type, true, W_change )
           ){
             // veto Higgs inside qqx
             assert(next!=end_out);
             if( !boson.empty() && boson.front().type == ParticleID::h
             ){
               if(  (backward && boson.front().rapidity() < next->rapidity())
                 ||(!backward && boson.front().rapidity() > next->rapidity()))
               return non_resummable;
             }
             begin_out = std::next(next);
             return not_tested | (backward?qqxexb:qqxexf);
           }
         }
       }
       return non_resummable;
     }
 
     //! Returns all possible classifications from central emissions
     // the beginning points are changed s.t. after the the classification they
     // point to the end of the emission chain
     // sets W_change: + if Wp change
     //               0 if no change
     //               - if Wm change
     template<class OutIterator>
     size_t possible_central(
       OutIterator & begin_out, OutIterator const & end_out,
       int & W_change, std::vector<Particle> const & boson
     ){
       using namespace event_type;
       assert(boson.size() < 2);
       // if we already passed the central chain,
       // then it is not a valid all-order state
       if(std::distance(begin_out, end_out) < 0) return non_resummable;
       // keep track of all states that we don't test
       size_t possible = unob | unof
                           | qqxexb | qqxexf;
 
       // Find the first non-gluon/non-FKL
       while( (begin_out->type==pid::gluon) && (begin_out!=end_out) ){
         ++begin_out;
       }
       // end of chain -> FKL
       if( begin_out==end_out ){
         return possible | FKL;
       }
 
       // is this a qqbar-pair?
       // needs two partons in two separate jets
       auto next = std::next(begin_out);
       if( is_valid_impact_factor(
             begin_out->type, next->type, true, W_change )
       ){
         // veto Higgs inside qqx
         if( !boson.empty() && boson.front().type == ParticleID::h
             && boson.front().rapidity() > begin_out->rapidity()
             && boson.front().rapidity() < next->rapidity()
         ){
           return non_resummable;
         }
         begin_out = std::next(next);
         // remaining chain should be pure gluon/FKL
         for(; begin_out!=end_out; ++begin_out){
           if(begin_out->type != pid::gluon) return non_resummable;
         }
         return possible | qqxmid;
       }
       return non_resummable;
     }
 
     /**
      * \brief Checks for all event types
      * @param ev          Event
      * @returns           Event Type
      *
      */
     event_type::EventType classify(Event const & ev){
       using namespace event_type;
       if(! has_2_jets(ev))
         return no_2_jets;
       // currently we can't handle multiple boson states in the ME. So they are
       // considered "bad_final_state" even though the "classify" could work with
       // them.
       if(! final_state_ok(ev))
         return bad_final_state;
 
       // initialise variables
       auto const & in = ev.incoming();
 
       // range for current checks
       auto begin_out{ev.cbegin_partons()};
       auto end_out{ev.crbegin_partons()};
 
       assert(std::distance(begin(in), end(in)) == 2);
       assert(std::distance(begin_out, end_out.base()) >= 2);
       assert(std::is_sorted(begin_out, end_out.base(), rapidity_less{}));
 
       auto const boson{ filter_AWZH_bosons(ev.outgoing()) };
       // we only allow one boson through final_state_ok
       assert(boson.size()<=1);
 
       // keep track of potential W couplings, at the end the sum should be 0
       int remaining_Wp = 0;
       int remaining_Wm = 0;
       if(!boson.empty() && std::abs(boson.front().type) == ParticleID::Wp ){
         if(boson.front().type>0) ++remaining_Wp;
         else ++remaining_Wm;
       }
       int W_change = 0;
 
       size_t final_type = ~(no_2_jets | bad_final_state);
 
       // check forward impact factor
       final_type &= possible_impact_factors(
         in.front().type,
         begin_out, end_out.base(),
         W_change, boson, true );
       if( final_type == non_resummable )
         return non_resummable;
       if(W_change>0) remaining_Wp-=W_change;
       else if(W_change<0) remaining_Wm+=W_change;
       W_change = 0;
 
       // check backward impact factor
       final_type &= possible_impact_factors(
         in.back().type,
         end_out, std::make_reverse_iterator(begin_out),
         W_change, boson, false );
       if( final_type == non_resummable )
         return non_resummable;
       if(W_change>0) remaining_Wp-=W_change;
       else if(W_change<0) remaining_Wm+=W_change;
       W_change = 0;
 
       // check central emissions
       final_type &= possible_central(
         begin_out, end_out.base(), W_change, boson );
       if( final_type == non_resummable )
         return non_resummable;
       if(W_change>0) remaining_Wp-=W_change;
       else if(W_change<0) remaining_Wm+=W_change;
 
       // Check whether the right number of Ws are present
       if( remaining_Wp != 0 || remaining_Wm != 0 ) return non_resummable;
 
       // result has to be unique
       if( (final_type & (final_type-1)) != 0) return non_resummable;
 
       // check that each sub processes is implemented
       // (has to be done at the end)
       if( (final_type & ~implemented_types(boson)) != 0 )
         return non_resummable;
 
       return static_cast<EventType>(final_type);
     }
     //@}
 
     Particle extract_particle(LHEF::HEPEUP const & hepeup, size_t i){
       auto id = static_cast<ParticleID>(hepeup.IDUP[i]);
       auto colour = is_parton(id)?hepeup.ICOLUP[i]:optional<Colour>();
       return { id,
                { hepeup.PUP[i][0], hepeup.PUP[i][1],
                  hepeup.PUP[i][2], hepeup.PUP[i][3] },
                colour
              };
     }
 
     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
 
   Event::EventData::EventData(LHEF::HEPEUP const & hepeup){
     parameters.central = EventParameters{
       hepeup.scales.mur, hepeup.scales.muf, hepeup.XWGTUP
     };
     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] == LHE_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));
     }
 
     // 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 const & ev,
     fastjet::JetDefinition const & jet_def, double const min_jet_pt
   ):
     Event( Event::EventData{
       ev.incoming, ev.outgoing, ev.decays,
       Parameters<EventParameters>{ev.central, ev.variations}
     }.cluster(jet_def, min_jet_pt) )
   {}
 
   //! @TODO remove in HEJ 2.2.0
   UnclusteredEvent::UnclusteredEvent(LHEF::HEPEUP const & hepeup){
       Event::EventData const evData{hepeup};
       incoming = evData.incoming;
       outgoing = evData.outgoing;
       decays = evData.decays;
       central = evData.parameters.central;
       variations = evData.parameters.variations;
   }
 
   void Event::EventData::sort(){
     // sort particles
     std::sort(
         begin(incoming), end(incoming),
         [](Particle const & o1, Particle const & o2){return o1.p.pz()<o2.p.pz();}
     );
 
     auto old_outgoing = std::move(outgoing);
     std::vector<size_t> idx(old_outgoing.size());
     std::iota(idx.begin(), idx.end(), 0);
     std::sort(idx.begin(), idx.end(), [&old_outgoing](size_t i, size_t j){
       return old_outgoing[i].rapidity() < old_outgoing[j].rapidity();
     });
     outgoing.clear();
     outgoing.reserve(old_outgoing.size());
     for(size_t i: idx) {
       outgoing.emplace_back(std::move(old_outgoing[i]));
     }
 
     // find decays again
     if(!decays.empty()){
       auto old_decays = std::move(decays);
       decays.clear();
       for(size_t i=0; i<idx.size(); ++i) {
         auto decay = old_decays.find(idx[i]);
         if(decay != old_decays.end())
           decays.emplace(i, std::move(decay->second));
       }
       assert(old_decays.size() == decays.size());
     }
   }
 
   namespace {
     Particle reconstruct_boson(std::vector<Particle> const & leptons) {
       Particle decayed_boson;
       decayed_boson.p = leptons[0].p + leptons[1].p;
       const int pidsum = leptons[0].type + leptons[1].type;
       if(pidsum == +1) {
         assert(is_antilepton(leptons[0]));
         if(is_antineutrino(leptons[0])) {
           throw not_implemented{"lepton-flavour violating final state"};
         }
         assert(is_neutrino(leptons[1]));
         // charged antilepton + neutrino means we had a W+
         decayed_boson.type = pid::Wp;
       }
       else if(pidsum == -1) {
         assert(is_antilepton(leptons[0]));
         if(is_neutrino(leptons[1])) {
           throw not_implemented{"lepton-flavour violating final state"};
         }
         assert(is_antineutrino(leptons[0]));
         // charged lepton + antineutrino means we had a W-
         decayed_boson.type = pid::Wm;
       }
       else if(pidsum == 0) {
         assert(is_anylepton(leptons[0]));
         if(is_anyneutrino(leptons[0])) {
           throw not_implemented{"final state with two neutrinos"};
         }
         // charged lepton-antilepton pair means we had a Z/photon
         decayed_boson.type = pid::Z_photon_mix;
       }
       else {
         throw not_implemented{
           "final state with leptons "
             + name(leptons[0].type)
             + " and "
             + name(leptons[1].type)
         };
       }
       return decayed_boson;
     }
   } // namespace
 
   void Event::EventData::reconstruct_intermediate() {
     const auto begin_leptons = std::partition(
         begin(outgoing), end(outgoing),
         [](Particle const & p) {return !is_anylepton(p);}
     );
     // We can only reconstruct FS with 2 leptons
     if(std::distance(begin_leptons, end(outgoing)) != 2) return;
     std::vector<Particle> leptons(begin_leptons, end(outgoing));
     std::sort(
         begin(leptons), end(leptons),
         [](Particle const & p0, Particle const & p1) {
           assert(is_anylepton(p0) && is_anylepton(p1));
           return p0.type < p1.type;
         }
     );
     // `reconstruct_boson` can throw, it should therefore be called before
     // changing `outgoing` to allow the user to recover the original EventData
     auto boson = reconstruct_boson(leptons);
     outgoing.erase(begin_leptons, end(outgoing));
     outgoing.emplace_back(std::move(boson));
     decays.emplace(outgoing.size()-1, std::move(leptons));
   }
 
   Event Event::EventData::cluster(
       fastjet::JetDefinition const & jet_def, double const min_jet_pt
   ){
     sort();
     return Event{ std::move(incoming), std::move(outgoing), std::move(decays),
       std::move(parameters),
       jet_def, min_jet_pt
     };
   }
 
   Event::Event(
       std::array<Particle, 2> && incoming,
       std::vector<Particle> && outgoing,
       std::unordered_map<size_t, std::vector<Particle>> && decays,
       Parameters<EventParameters> && parameters,
       fastjet::JetDefinition const & jet_def,
       double const min_jet_pt
     ): incoming_{std::move(incoming)},
        outgoing_{std::move(outgoing)},
        decays_{std::move(decays)},
        parameters_{std::move(parameters)},
        cs_{ to_PseudoJet( filter_partons(outgoing_) ), jet_def },
        min_jet_pt_{min_jet_pt}
     {
       jets_ = sorted_by_rapidity(cs_.inclusive_jets(min_jet_pt_));
       assert(std::is_sorted(begin(outgoing_), end(outgoing_),
         rapidity_less{}));
       type_ = classify(*this);
     }
 
   namespace {
     //! check that Particles have a reasonable colour
     bool correct_colour(Particle const & part){
       ParticleID id{ part.type };
       if(!is_parton(id))
         return !part.colour;
 
       if(!part.colour)
         return false;
 
       Colour const & col{ *part.colour };
       if(is_quark(id))
         return col.first != 0 && col.second == 0;
       if(is_antiquark(id))
         return col.first == 0 && col.second != 0;
       assert(id==ParticleID::gluon);
       return col.first != 0 && col.second != 0 && col.first != col.second;
     }
 
     //! Connect parton to t-channel colour line & update the line
     //! returns false if connection not possible
     template<class OutIterator>
     bool try_connect_t(OutIterator const & it_part, Colour & line_colour){
       if( line_colour.first == it_part->colour->second ){
         line_colour.first = it_part->colour->first;
         return true;
       }
       if( line_colour.second == it_part->colour->first ){
         line_colour.second = it_part->colour->second;
         return true;
       }
       return false;
     }
 
     //! Connect parton to u-channel colour line & update the line
     //! returns false if connection not possible
     template<class OutIterator>
     bool try_connect_u(OutIterator & it_part, Colour & line_colour){
       auto it_next = std::next(it_part);
       if( try_connect_t(it_next, line_colour)
           && try_connect_t(it_part, line_colour)
       ){
         it_part=it_next;
         return true;
       }
       return false;
     }
   } // namespace
 
   bool Event::is_leading_colour() const {
     if( !correct_colour(incoming()[0]) || !correct_colour(incoming()[1]) )
       return false;
 
     Colour line_colour = *incoming()[0].colour;
     std::swap(line_colour.first, line_colour.second);
 
     // reasonable colour
     if(!std::all_of(outgoing().cbegin(), outgoing().cend(), correct_colour))
       return false;
 
     for(auto it_part = cbegin_partons(); it_part!=cend_partons(); ++it_part){
 
       switch (type()) {
       case event_type::FKL:
         if( !try_connect_t(it_part, line_colour) )
           return false;
         break;
       case event_type::unob:
       case event_type::qqxexb: {
         if( !try_connect_t(it_part, line_colour)
             // u-channel only allowed at impact factor
             && (std::distance(cbegin_partons(), it_part)!=0
                 || !try_connect_u(it_part, line_colour)))
           return false;
         break;
       }
       case event_type::unof:
       case event_type::qqxexf: {
         if( !try_connect_t(it_part, line_colour)
             // u-channel only allowed at impact factor
             && (std::distance(it_part, cend_partons())!=2
                 || !try_connect_u(it_part, line_colour)))
           return false;
         break;
       }
       case event_type::qqxmid:{
         auto it_next = std::next(it_part);
         if( !try_connect_t(it_part, line_colour)
             // u-channel only allowed at qqx/qxq pair
             && ( (   !(is_quark(*it_part) && is_antiquark(*it_next))
                   && !(is_antiquark(*it_part) && is_quark(*it_next)))
                 || !try_connect_u(it_part, line_colour))
           )
           return false;
         break;
       }
       default:
         throw std::logic_error{"unreachable"};
       }
 
       // no colour singlet exchange/disconnected diagram
       if(line_colour.first == line_colour.second)
         return false;
     }
 
     return (incoming()[1].colour->first == line_colour.first)
         && (incoming()[1].colour->second == line_colour.second);
   }
 
   namespace {
     //! connect incoming Particle to colour flow
     void connect_incoming(Particle & in, int & colour, int & anti_colour){
       in.colour = std::make_pair(anti_colour, colour);
       // gluon
       if(in.type == pid::gluon)
         return;
       if(in.type > 0){
         // quark
         assert(is_quark(in));
         in.colour->second = 0;
         colour*=-1;
         return;
       }
       // anti-quark
       assert(is_antiquark(in));
       in.colour->first = 0;
       anti_colour*=-1;
    }
 
     //! connect outgoing Particle to t-channel colour flow
     template<class OutIterator>
     void connect_tchannel(
         OutIterator & it_part, int & colour, int & anti_colour, RNG & ran
     ){
       assert(colour>0 || anti_colour>0);
       if(it_part->type == ParticleID::gluon){
         // gluon
         if(colour>0 && anti_colour>0){
           // on g line => connect to colour OR anti-colour (random)
           if(ran.flat() < 0.5){
             it_part->colour = std::make_pair(colour+2,colour);
             colour+=2;
           } else {
             it_part->colour = std::make_pair(anti_colour, anti_colour+2);
             anti_colour+=2;
           }
         } else if(colour > 0){
           // on q line => connect to available colour
             it_part->colour = std::make_pair(colour+2, colour);
             colour+=2;
         } else {
           assert(colour<0 && anti_colour>0);
           // on qx line => connect to available anti-colour
           it_part->colour = std::make_pair(anti_colour, anti_colour+2);
           anti_colour+=2;
         }
       } else if(is_quark(*it_part)) {
         // quark
         assert(anti_colour>0);
         if(colour>0){
           // on g line => connect and remove anti-colour
           it_part->colour = std::make_pair(anti_colour, 0);
           anti_colour+=2;
           anti_colour*=-1;
         } else {
           // on qx line => new colour
           colour*=-1;
           it_part->colour = std::make_pair(colour, 0);
         }
       } else if(is_antiquark(*it_part)) {
         // anti-quark
         assert(colour>0);
         if(anti_colour>0){
           // on g line => connect and remove colour
           it_part->colour = std::make_pair(0, colour);
           colour+=2;
           colour*=-1;
         } else {
           // on q line => new anti-colour
           anti_colour*=-1;
           it_part->colour = std::make_pair(0, anti_colour);
         }
       } else { // not a parton
         assert(!is_parton(*it_part));
         it_part->colour = {};
       }
     }
 
     //! connect to t- or u-channel colour flow
     template<class OutIterator>
     void connect_utchannel(
         OutIterator & it_part, int & colour, int & anti_colour, RNG & ran
     ){
       OutIterator it_first = it_part++;
       if(ran.flat()<.5) {// t-channel
         connect_tchannel(it_first, colour, anti_colour, ran);
         connect_tchannel(it_part, colour, anti_colour, ran);
       }
       else { // u-channel
         connect_tchannel(it_part, colour, anti_colour, ran);
         connect_tchannel(it_first, colour, anti_colour, ran);
       }
     }
   } // namespace
 
   bool Event::generate_colours(RNG & ran){
     // generate only for HEJ events
     if(!event_type::is_resummable(type()))
       return false;
     assert(std::is_sorted(
       begin(outgoing()), end(outgoing()), rapidity_less{}));
     assert(incoming()[0].pz() < incoming()[1].pz());
 
     // positive (anti-)colour -> can connect
     // negative (anti-)colour -> not available/used up by (anti-)quark
     int colour = COLOUR_OFFSET;
     int anti_colour = colour+1;
     // initialise first
     connect_incoming(incoming_[0], colour, anti_colour);
 
     // reset outgoing colours
     std::for_each(outgoing_.begin(), outgoing_.end(),
       [](Particle & part){ part.colour = {};});
 
     for(auto it_part = begin_partons(); it_part!=end_partons(); ++it_part){
         switch (type()) {
         // subleading can connect to t- or u-channel
         case event_type::unob:
         case event_type::qqxexb: {
           if( std::distance(begin_partons(), it_part)==0)
             connect_utchannel(it_part, colour, anti_colour, ran);
           else
             connect_tchannel(it_part, colour, anti_colour, ran);
           break;
         }
         case event_type::unof:
         case event_type::qqxexf: {
           if( std::distance(it_part, end_partons())==2)
             connect_utchannel(it_part, colour, anti_colour, ran);
           else
             connect_tchannel(it_part, colour, anti_colour, ran);
           break;
         }
         case event_type::qqxmid:{
           auto it_next = std::next(it_part);
           if( std::distance(begin_partons(), it_part)>0
               && std::distance(it_part, end_partons())>2
               && ( (is_quark(*it_part) && is_antiquark(*it_next))
                 || (is_antiquark(*it_part) && is_quark(*it_next)) )
           )
             connect_utchannel(it_part, colour, anti_colour, ran);
           else
             connect_tchannel(it_part, colour, anti_colour, ran);
           break;
         }
         default: // rest has to be t-channel
           connect_tchannel(it_part, colour, anti_colour, ran);
         }
     }
     // Connect last
     connect_incoming(incoming_[1], anti_colour, colour);
     assert(is_leading_colour());
     return true;
   } // generate_colours
 
   namespace {
     bool valid_parton(
       std::vector<fastjet::PseudoJet> const & jets,
       Particle const & parton, int const idx,
       double const max_ext_soft_pt_fraction, double const min_extparton_pt
     ){
       // TODO code overlap with PhaseSpacePoint::pass_extremal_cuts
       if(min_extparton_pt > parton.pt()) return false;
       if(idx<0) return false;
       assert(static_cast<int>(jets.size())>=idx);
       auto const & jet{ jets[idx] };
       return (parton.p - jet).pt()/jet.pt() <= max_ext_soft_pt_fraction;
     }
   } // namespace
 
   // this should work with multiple types
   bool Event::valid_hej_state(double const max_frac,
                               double const min_pt
   ) const {
     using namespace event_type;
     if(!is_resummable(type()))
       return false;
 
     auto const & jet_idx{ particle_jet_indices() };
     auto idx_begin{ jet_idx.cbegin() };
     auto idx_end{  jet_idx.crbegin() };
 
     auto part_begin{ cbegin_partons() };
     auto part_end{  crbegin_partons() };
 
     // always seperate extremal jets
     if( !valid_parton(jets(), *part_begin, *idx_begin, max_frac, min_pt) )
       return false;
     ++part_begin;
     ++idx_begin;
     if( !valid_parton(jets(), *part_end,   *idx_end,   max_frac, min_pt) )
       return false;
     ++part_end;
     ++idx_end;
 
     // unob -> second parton in own jet
     if( type() & (unob | qqxexb) ){
       if( !valid_parton(jets(), *part_begin, *idx_begin, max_frac, min_pt) )
         return false;
       ++part_begin;
       ++idx_begin;
     }
 
     if( type() & (unof | qqxexf) ){
       if( !valid_parton(jets(), *part_end,   *idx_end,   max_frac, min_pt) )
         return false;
       ++part_end;
       // ++idx_end; // last check, we don't need idx_end afterwards
     }
 
     if( type() & qqxmid ){
       // find qqx pair
       auto begin_qqx{ std::find_if( part_begin, part_end.base(),
         [](Particle const & part) -> bool {
           return part.type != ParticleID::gluon;
         }
       )};
       assert(begin_qqx != part_end.base());
       long int qqx_pos{ std::distance(part_begin, begin_qqx) };
       assert(qqx_pos >= 0);
       idx_begin+=qqx_pos;
       if( !( valid_parton(jets(),*begin_qqx,    *idx_begin,    max_frac,min_pt)
           && valid_parton(jets(),*(++begin_qqx),*(++idx_begin),max_frac,min_pt)
       ))
         return false;
     }
     return true;
   }
 
   Event::ConstPartonIterator Event::begin_partons() const {
     return cbegin_partons();
   }
   Event::ConstPartonIterator Event::cbegin_partons() const {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(Particle const &)>(is_parton),
-        cbegin(outgoing()),
-        cend(outgoing())
-    );
+    return {HEJ::is_parton, cbegin(outgoing()), cend(outgoing())};
   }
 
   Event::ConstPartonIterator Event::end_partons() const {
     return cend_partons();
   }
   Event::ConstPartonIterator Event::cend_partons() const {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(Particle const &)>(is_parton),
-        cend(outgoing()),
-        cend(outgoing())
-    );
+    return {HEJ::is_parton, cend(outgoing()), cend(outgoing())};
   }
 
   Event::ConstReversePartonIterator Event::rbegin_partons() const {
     return crbegin_partons();
   }
   Event::ConstReversePartonIterator Event::crbegin_partons() const {
     return std::reverse_iterator<ConstPartonIterator>( cend_partons() );
   }
 
   Event::ConstReversePartonIterator Event::rend_partons() const {
     return crend_partons();
   }
   Event::ConstReversePartonIterator Event::crend_partons() const {
     return std::reverse_iterator<ConstPartonIterator>( cbegin_partons() );
   }
 
   Event::PartonIterator Event::begin_partons() {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(Particle const &)>(is_parton),
-        begin(outgoing_),
-        end(outgoing_)
-    );
+    return {HEJ::is_parton, begin(outgoing_), end(outgoing_)};
   }
 
   Event::PartonIterator Event::end_partons() {
-    return boost::make_filter_iterator(
-        static_cast<bool (*)(Particle const &)>(is_parton),
-        end(outgoing_),
-        end(outgoing_)
-    );
+    return {HEJ::is_parton, end(outgoing_), end(outgoing_)};
   }
 
   Event::ReversePartonIterator Event::rbegin_partons() {
     return std::reverse_iterator<PartonIterator>( end_partons() );
   }
 
   Event::ReversePartonIterator Event::rend_partons() {
     return std::reverse_iterator<PartonIterator>( begin_partons() );
   }
 
   namespace {
     void print_momentum(std::ostream & os, fastjet::PseudoJet const & part){
       constexpr int prec = 6;
       const std::streamsize orig_prec = os.precision();
       os <<std::scientific<<std::setprecision(prec) << "["
         <<std::setw(2*prec+1)<<std::right<< part.px() << ", "
         <<std::setw(2*prec+1)<<std::right<< part.py() << ", "
         <<std::setw(2*prec+1)<<std::right<< part.pz() << ", "
         <<std::setw(2*prec+1)<<std::right<< part.E() << "]"<< std::fixed;
       os.precision(orig_prec);
     }
 
     void print_colour(std::ostream & os, optional<Colour> const & col){
       constexpr int width = 3;
       if(!col)
         os << "(no color)"; // American spelling for better alignment
       else
         os << "("  <<std::setw(width)<<std::right<< col->first
            << ", " <<std::setw(width)<<std::right<< col->second << ")";
     }
   } // namespace
 
   std::ostream& operator<<(std::ostream & os, Event const & ev){
     constexpr int prec = 4;
     constexpr int wtype = 3; // width for types
     const std::streamsize orig_prec = os.precision();
     os <<std::setprecision(prec)<<std::fixed;
     os << "########## " << name(ev.type()) << " ##########" << std::endl;
     os << "Incoming particles:\n";
     for(auto const & in: ev.incoming()){
       os <<std::setw(wtype)<< in.type << ": ";
       print_colour(os, in.colour);
       os << " ";
       print_momentum(os, in.p);
       os << std::endl;
     }
     os << "\nOutgoing particles: " << ev.outgoing().size() << "\n";
     for(auto const & out: ev.outgoing()){
       os <<std::setw(wtype)<< out.type << ": ";
       print_colour(os, out.colour);
       os << " ";
       print_momentum(os, out.p);
       os << " => rapidity="
         <<std::setw(2*prec-1)<<std::right<< out.rapidity() << std::endl;
     }
     os << "\nForming Jets: " << ev.jets().size() << "\n";
     for(auto const & jet: ev.jets()){
       print_momentum(os, jet);
       os << " => rapidity="
         <<std::setw(2*prec-1)<<std::right<< jet.rapidity() << std::endl;
     }
     if(!ev.decays().empty() ){
       os << "\nDecays: " << ev.decays().size() << "\n";
       for(auto const & decay: ev.decays()){
         os <<std::setw(wtype)<< ev.outgoing()[decay.first].type
           << " (" << decay.first << ") to:\n";
         for(auto const & out: decay.second){
           os <<"  "<<std::setw(wtype)<< out.type << ": ";
           print_momentum(os, out.p);
           os << " => rapidity="
             <<std::setw(2*prec-1)<<std::right<< out.rapidity() << std::endl;
         }
       }
 
     }
     os << std::defaultfloat;
     os.precision(orig_prec);
     return os;
   }
 
   double shat(Event const & ev){
     return (ev.incoming()[0].p + ev.incoming()[1].p).m2();
   }
 
   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();  // event type
     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;
 
     result.IDUP.reserve(num_particles);   // PID
     result.ISTUP.reserve(num_particles);  // status (in, out, decay)
     result.PUP.reserve(num_particles);    // momentum
     result.MOTHUP.reserve(num_particles); // index mother particle
     result.ICOLUP.reserve(num_particles); // colour
     // incoming
     std::array<Particle, 2> incoming{ event.incoming() };
     // First incoming should be positive pz according to LHE standard
     // (or at least most (everyone?) do it this way, and Pythia assumes it)
     if(incoming[0].pz() < incoming[1].pz())
       std::swap(incoming[0], incoming[1]);
     for(Particle const & in: incoming){
       result.IDUP.emplace_back(in.type);
       result.ISTUP.emplace_back(LHE_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);
       assert(in.colour);
       result.ICOLUP.emplace_back(*in.colour);
     }
     // outgoing
     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) != 0u
                           ?LHE_Status::decay
                           :LHE_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);
       if(out.colour)
         result.ICOLUP.emplace_back(*out.colour);
       else{
         result.ICOLUP.emplace_back(std::make_pair(0,0));
       }
     }
     // decays
     for(auto const & decay: event.decays()){
       for(auto const & out: decay.second){
         result.IDUP.emplace_back(out.type);
         result.ISTUP.emplace_back(LHE_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;
   }
 
 } // namespace HEJ