diff --git a/FixedOrderGen/src/PhaseSpacePoint.cc b/FixedOrderGen/src/PhaseSpacePoint.cc
index fad6bbe..3ae9d00 100644
--- a/FixedOrderGen/src/PhaseSpacePoint.cc
+++ b/FixedOrderGen/src/PhaseSpacePoint.cc
@@ -1,916 +1,920 @@
 /**
  *  \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())
     );
   }
 
   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())
     );
   }
 
   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_)
     );
   }
 
   PhaseSpacePoint::PartonIterator PhaseSpacePoint::end_partons() {
     return boost::make_filter_iterator(
         static_cast<bool (*)(HEJ::Particle const &)>(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 const subl_channels,
+    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 ~0;
       }
       // 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?0b00011001101
                     :0b00100110011;
     }
   }
 
   /**
    * @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
   ){
     std::array<part_mask,2> allowed_partons{
         init_allowed(proc.incoming[0]),
         init_allowed(proc.incoming[1])
       };
     // special case A/W/Z && central qqx not possible
     if(is_AWZ_proccess(proc)
         && ((proc.njets < 4) || !subl_channels[subleading::cqqx])
     ){
       // all possible incoming states
       auto allowed = allowed_quarks(*proc.boson);
       if(proc.njets == 2 || !subl_channels[subleading::eqqx]){
         allowed.reset(0);
       }
 
       // possible states per leg
       std::array<part_mask,2> const maybe_partons{
         allowed_partons[0]&allowed, allowed_partons[1]&allowed};
 
       if(maybe_partons[0].any() && maybe_partons[1].any()){
         // two options to get allowed initial state => choose one at random
         const size_t idx = ran.flat() < 0.5;
         allowed_partons[idx] = maybe_partons[idx];
         //! @TODO Is this factor correct? I think so wasn't there before
         weight_*=2.;
         // else choose the possible
       } else if(maybe_partons[0].any()) {
         allowed_partons[0] = maybe_partons[0];
       } else if(maybe_partons[1].any()) {
         allowed_partons[1] = maybe_partons[1];
       } 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;
   }
 }