diff --git a/FixedOrderGen/src/PhaseSpacePoint.cc b/FixedOrderGen/src/PhaseSpacePoint.cc index 63ac4df..523b7bd 100644 --- a/FixedOrderGen/src/PhaseSpacePoint.cc +++ b/FixedOrderGen/src/PhaseSpacePoint.cc @@ -1,455 +1,462 @@ #include "PhaseSpacePoint.hh" #include <random> #include "RHEJ/kinematics.hh" #include "RHEJ/utility.hh" #include "RHEJ/exceptions.hh" #include "Process.hh" #include <CLHEP/Random/Randomize.h> #include <CLHEP/Random/RanluxEngine.h> using namespace RHEJ; namespace HEJFOG{ static_assert( std::numeric_limits<double>::has_quiet_NaN, "no quiet NaN for double" ); constexpr double NaN = std::numeric_limits<double>::quiet_NaN(); RHEJ::UnclusteredEvent to_UnclusteredEvent(PhaseSpacePoint const & psp){ RHEJ::UnclusteredEvent result; result.incoming = psp.incoming(); std::sort( begin(result.incoming), end(result.incoming), [](Particle o1, Particle o2){return o1.p.pz()<o2.p.pz();} ); assert(result.incoming.size() == 2); result.outgoing = psp.outgoing(); assert( std::is_sorted( begin(result.outgoing), end(result.outgoing), RHEJ::rapidity_less{} ) ); assert(result.outgoing.size() >= 2); result.decays = psp.decays(); result.central.mur = NaN; result.central.muf = NaN; result.central.weight = psp.weight(); return result; } namespace{ bool can_swap_to_uno( RHEJ::Particle const & p1, RHEJ::Particle const & p2 ){ return is_parton(p1) && p1.type != RHEJ::pid::gluon && p2.type == RHEJ::pid::gluon; } } void PhaseSpacePoint::maybe_turn_to_uno( double chance, RHEJ::RNG & ran ){ assert(outgoing_.size() >= 2); const size_t nout = outgoing_.size(); const bool can_be_uno_backward = can_swap_to_uno( outgoing_[0], outgoing_[1] ); const bool can_be_uno_forward = can_swap_to_uno( outgoing_[nout-1], outgoing_[nout-2] ); if(!can_be_uno_backward && !can_be_uno_forward) return; if(ran.flat() < chance){ weight_ /= chance; if(can_be_uno_backward && can_be_uno_forward){ if(ran.flat() < 0.5){ std::swap(outgoing_[0].type, outgoing_[1].type); } else{ std::swap(outgoing_[nout-1].type, outgoing_[nout-2].type); } weight_ *= 2.; } else if(can_be_uno_backward){ std::swap(outgoing_[0].type, outgoing_[1].type); } else{ assert(can_be_uno_forward); std::swap(outgoing_[nout-1].type, outgoing_[nout-2].type); } } else weight_ /= 1 - chance; } PhaseSpacePoint::PhaseSpacePoint( Process const & proc, JetParameters const & jet_param, RHEJ::PDF & pdf, double E_beam, double uno_chance, HiggsProperties const & h, RHEJ::RNG & ran ) { assert(proc.njets >= 2); const int nout = proc.njets + (proc.boson?1:0); status_ = good; weight_ = 1; weight_ /= std::tgamma(nout); outgoing_.reserve(nout); for(auto&& p_out: gen_LO_partons(proc.njets, jet_param, E_beam, ran)){ outgoing_.emplace_back(Particle{pid::gluon, std::move(p_out)}); } if(status_ != good) return; if(proc.boson && *proc.boson == pid::Higgs){ // The Higgs auto Hparticle=gen_boson(pid::higgs, h.mass, h.width, ran); auto pos=std::upper_bound( begin(outgoing_),end(outgoing_),Hparticle,rapidity_less{} ); outgoing_.insert(pos, Hparticle); if(! h.decays.empty()){ const int boson_idx = std::distance(begin(outgoing_), pos); decays_.emplace( boson_idx, decay_boson(outgoing_[boson_idx], h.decays, ran) ); } } reconstruct_incoming(proc.incoming, pdf, E_beam, jet_param.min_pt, ran); if(status_ != good) return; // set outgoing states most_backward_FKL(outgoing_).type = incoming_[0].type; most_forward_FKL(outgoing_).type = incoming_[1].type; if(proc.njets > 2) maybe_turn_to_uno(uno_chance, ran); } double PhaseSpacePoint::gen_hard_pt( int np , double ptmin, double ptmax, double y, RHEJ::RNG & ran ) { // heuristic parameters for pt sampling const double ptpar = ptmin + np/5.; const double arg_small_y = atan((ptmax - ptmin)/ptpar); const double y_cut = 3.; const double r1 = ran.flat(); if(y < y_cut){ const double pt = ptmin + ptpar*tan(r1*arg_small_y); const double temp = cos(r1*arg_small_y); weight_ *= pt*ptpar*arg_small_y/(temp*temp); return pt; } const double ptpar2 = ptpar/(1 + 5*(y-y_cut)); const double temp = 1. - std::exp((ptmin-ptmax)/ptpar2); const double pt = ptmin - ptpar2*std::log(1-r1*temp); weight_ *= pt*ptpar2*temp/(1-r1*temp); return pt; } double PhaseSpacePoint::gen_soft_pt(int np, double max_pt, RHEJ::RNG & ran) { constexpr double ptpar = 4.; const double r = ran.flat(); weight_ *= ptpar/(np*r); return max_pt + ptpar/np*std::log(r); } double PhaseSpacePoint::gen_parton_pt( int count, JetParameters const & jet_param, double max_pt, double y, RHEJ::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; - return gen_soft_pt(count, *jet_param.peak_pt, ran); + const double pt = gen_soft_pt(count, *jet_param.peak_pt, ran); + if(pt < jet_param.min_pt) { + weight_=0.0; + status_ = not_enough_jets; + return jet_param.min_pt; + } + return pt; } std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_LO_partons( int np , JetParameters const & jet_param, double max_pt, RHEJ::RNG & ran ){ if (np<2) throw std::invalid_argument{"Not enough partons in gen_LO_partons"}; weight_ /= pow(16.*pow(M_PI,3),np-2); 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 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-1e-5 <= partons[i].pt()); + 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_ = not_enough_jets; return {}; } std::sort(begin(partons), end(partons), rapidity_less{}); return partons; } Particle PhaseSpacePoint::gen_boson( RHEJ::ParticleID bosonid, double mass, double width, RHEJ::RNG & ran ){ std::array<double,2> ptrans{0.,0.}; for (auto const & parton:outgoing_) { ptrans[0]-=parton.px(); ptrans[1]-=parton.py(); } // The Higgs: // Generate a y Gaussian distributed around 0 const double y = random_normal(1.6, ran); const double r1 = ran.flat(); const double sH = mass*( mass + width*tan(M_PI/2.*r1 + (r1-1.)*atan(mass/width)) ); const double mHperp=sqrt(ptrans[0]*ptrans[0]+ptrans[1]*ptrans[1]+sH); const double pz=mHperp*sinh(y); const double E=mHperp*cosh(y); return Particle{bosonid,fastjet::PseudoJet{ptrans[0],ptrans[1],pz,E}}; } Particle const & PhaseSpacePoint::most_backward_FKL( std::vector<Particle> const & partons ) const{ if(!RHEJ::is_parton(partons[0])) return partons[1]; return partons[0]; } Particle const & PhaseSpacePoint::most_forward_FKL( std::vector<Particle> const & partons ) const{ const size_t last_idx = partons.size() - 1; if(!RHEJ::is_parton(partons[last_idx])) return partons[last_idx-1]; return partons[last_idx]; } Particle & PhaseSpacePoint::most_backward_FKL( std::vector<Particle> & partons ) const{ if(!RHEJ::is_parton(partons[0])) return partons[1]; return partons[0]; } Particle & PhaseSpacePoint::most_forward_FKL( std::vector<Particle> & partons ) const{ const size_t last_idx = partons.size() - 1; if(!RHEJ::is_parton(partons[last_idx])) return partons[last_idx-1]; return partons[last_idx]; } void PhaseSpacePoint::reconstruct_incoming( std::array<RHEJ::ParticleID, 2> const & ids, RHEJ::PDF & pdf, double E_beam, double uf, RHEJ::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].p.e()-incoming_[0].p.pz())/sqrts; const double xb=(incoming_[1].p.e()+incoming_[1].p.pz())/sqrts; // abort if phase space point is outside of collider energy reach if (xa>1. || xb>1.){ weight_=0; status_ = too_much_energy; return; } // pick pdfs /** TODO: * ufa, ufb don't correspond to our final scale choice. * The reversed HEJ scale generators currently expect a full event as input, * so fixing this is not completely trivial */ if(ids[0] == pid::proton || ids[0] == pid::p_bar){ const double ufa=uf; incoming_[0].type = generate_incoming_id(xa, ufa, pdf, ran); } else { incoming_[0].type = ids[0]; } if(ids[1] == pid::proton || ids[1] == pid::p_bar){ const double ufb=uf; incoming_[1].type = generate_incoming_id(xb, ufb, pdf, ran); } else { incoming_[1].type = ids[1]; } assert(momentum_conserved(1e-7)); } RHEJ::ParticleID PhaseSpacePoint::generate_incoming_id( double x, double uf, RHEJ::PDF & pdf, RHEJ::RNG & ran ){ const double pdfg=fabs(pdf.pdfpt(0,x,uf,pid::gluon)); const double pdfu=fabs(pdf.pdfpt(0,x,uf,pid::up)); const double pdfd=fabs(pdf.pdfpt(0,x,uf,pid::down)); const double pdfux=fabs(pdf.pdfpt(0,x,uf,pid::u_bar)); const double pdfdx=fabs(pdf.pdfpt(0,x,uf,pid::d_bar)); const double pdfc=fabs(pdf.pdfpt(0,x,uf,pid::charm)); const double pdfs=fabs(pdf.pdfpt(0,x,uf,pid::strange)); const double pdfsx=fabs(pdf.pdfpt(0,x,uf,pid::s_bar)); const double pdfb=fabs(pdf.pdfpt(0,x,uf,pid::b)); const double pdftot=pdfg+4.0/9.0*(pdfu + pdfd + pdfux + pdfdx +pdfs +pdfsx + 2.0*(pdfc +pdfb )); const double r1=pdftot*ran.flat(); double sum; if (r1<(sum=pdfg)) { weight_*=pdftot/pdfg; return pid::gluon; } if (r1<(sum+=(4./9.)*pdfu)) { weight_*=pdftot/((4./9.)*pdfu); return pid::up; } else if (r1<(sum+=(4./9.)*pdfd)) { weight_*=pdftot/((4./9.)*pdfd); return pid::down; } else if (r1<(sum+=(4./9.)*pdfux)) { weight_*=pdftot/((4./9.)*pdfux); return pid::u_bar; } else if (r1<(sum+=(4./9.)*pdfdx)) { weight_*=pdftot/((4./9.)*pdfdx); return pid::d_bar; } else if (r1<(sum+=(4./9.)*pdfc)) { weight_*=pdftot/((4./9.)*pdfc); return pid::c; } else if (r1<(sum+=(4./9.)*pdfc)){ weight_*=pdftot/((4./9.)*pdfc); return pid::c_bar; } else if (r1<(sum+=(4./9.)*pdfs)) { weight_*=pdftot/((4./9.)*pdfs); return pid::s; } else if (r1<(sum+=(4./9.)*pdfsx)) { weight_*=pdftot/((4./9.)*pdfsx); return pid::s_bar; } else if (r1<(sum+=(4./9.)*pdfb)) { weight_*=pdftot/((4./9.)*pdfb); return pid::b; } else if (r1<=(sum+=(4./9.)*pdfb)) { weight_*=pdftot/((4./9.)*pdfb); return pid::b_bar; } std::cout << "Error in choosing incoming parton: "<<x<<" "<<uf<<" "<<sum<<" "<<pdftot<<" "<<r1; std::cout << " "<<pdfg+4./9.*(pdfu+pdfux+pdfd+pdfdx+pdfs+pdfsx+2.*(pdfc+pdfb))<<std::endl; throw std::logic_error{"Failed to choose parton flavour"}; } double PhaseSpacePoint::random_normal( double stddev, RHEJ::RNG & ran ){ const double r1 = ran.flat(); const double r2 = ran.flat(); const double lninvr1 = -log(r1); const double result = stddev*sqrt(2.*lninvr1)*cos(2.*M_PI*r2); weight_ *= exp(result*result/(2*stddev*stddev))*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, RHEJ::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; 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( RHEJ::Particle const & parent, std::vector<Decay> const & decays, RHEJ::RNG & ran ){ const auto channel = select_decay_channel(decays, ran); if(channel.products.size() != 2){ throw RHEJ::not_implemented{ "only decays into two particles are implemented" }; } std::vector<Particle> decay_products(channel.products.size()); for(size_t i = 0; i < channel.products.size(); ++i){ decay_products[i].type = channel.products[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.; const double sin_phi = sqrt(1. - cos_phi*cos_phi); // Know 0 < phi < pi const double px = E*cos(theta)*sin_phi; const double py = E*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; } }