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diff --git a/FixedOrderGen/include/PhaseSpacePoint.hh b/FixedOrderGen/include/PhaseSpacePoint.hh
index 957902d..4ab5d5b 100644
--- a/FixedOrderGen/include/PhaseSpacePoint.hh
+++ b/FixedOrderGen/include/PhaseSpacePoint.hh
@@ -1,164 +1,164 @@
/** \file PhaseSpacePoint.hh
* \brief Contains the PhaseSpacePoint Class
*/
#pragma once
#include <vector>
#include "HEJ/utility.hh"
#include "HEJ/Event.hh"
#include "HEJ/PDG_codes.hh"
#include "HEJ/PDF.hh"
#include "HEJ/RNG.hh"
#include "Status.hh"
#include "JetParameters.hh"
#include "ParticleProperties.hh"
namespace HEJFOG{
class Process;
using HEJ::Particle;
//! A point in resummation phase space
class PhaseSpacePoint{
public:
//! Default PhaseSpacePoint Constructor
PhaseSpacePoint() = default;
//! PhaseSpacePoint Constructor
/**
* @param proc The process to generate
* @param jet_def The Jet Definition Used
* @param jetptmin Minimum Jet Transverse Momentum
* @param rapmax Maximum parton rapidity
* @param pdf The pdf set (used for sampling)
* @param uno_chance Chance to turn a potentially unordered
* emission into an actual one
*
* Initially, only FKL phase space points are generated. If the most
* extremal emission in any direction is a quark or anti-quark and the
* next emission is a gluon, uno_chance is the chance to turn this into
* an unordered emission event by swapping the two flavours. At most one
* unordered emission will be generated in this way.
*/
PhaseSpacePoint(
Process const & proc,
JetParameters const & jet_properties,
HEJ::PDF & pdf, double E_beam,
double uno_chance,
ParticlesPropMap const & particles_properties,
HEJ::RNG & ran
);
//! Get Weight Function
/**
* @returns Weight of Event
*/
double weight() const{
return weight_;
}
Status status() const{
return status_;
}
//! Get Incoming Function
/**
* @returns Incoming Particles
*/
std::array<Particle, 2> const & incoming() const{
return incoming_;
}
//! Get Outgoing Function
/**
* @returns Outgoing Particles
*/
std::vector<Particle> const & outgoing() const{
return outgoing_;
}
- std::unordered_map<int, std::vector<Particle>> const & decays() const{
+ std::unordered_map<size_t, std::vector<Particle>> const & decays() const{
return decays_;
}
private:
std::vector<fastjet::PseudoJet> gen_LO_partons(
int count, bool is_pure_jets,
JetParameters const & jet_param,
double max_pt,
HEJ::RNG & ran
);
Particle gen_boson(
HEJ::ParticleID bosonid, double mass, double width,
HEJ::RNG & ran
);
template<class ParticleMomenta>
fastjet::PseudoJet gen_last_momentum(
ParticleMomenta const & other_momenta,
double mass_square, double y
) const;
bool jets_ok(
std::vector<fastjet::PseudoJet> const & Born_jets,
std::vector<fastjet::PseudoJet> const & partons
) const;
void reconstruct_incoming(
std::array<HEJ::ParticleID, 2> const & ids,
HEJ::PDF & pdf, double E_beam,
double uf,
HEJ::RNG & ran
);
HEJ::ParticleID generate_incoming_id(
size_t beam_idx, double x, double uf, HEJ::PDF & pdf,
HEJ::RNG & ran
);
bool momentum_conserved(double ep) const;
HEJ::Particle const & most_backward_FKL(
std::vector<HEJ::Particle> const & partons
) const;
HEJ::Particle const & most_forward_FKL(
std::vector<HEJ::Particle> const & partons
) const;
HEJ::Particle & most_backward_FKL(std::vector<HEJ::Particle> & partons) const;
HEJ::Particle & most_forward_FKL(std::vector<HEJ::Particle> & partons) const;
bool extremal_FKL_ok(
std::vector<fastjet::PseudoJet> const & partons
) const;
double random_normal(double stddev, HEJ::RNG & ran);
void maybe_turn_to_uno(double chance, HEJ::RNG & ran);
std::vector<Particle> decay_boson(
HEJ::Particle const & parent,
std::vector<Decay> const & decays,
HEJ::RNG & ran
);
Decay select_decay_channel(
std::vector<Decay> const & decays,
HEJ::RNG & ran
);
double gen_hard_pt(
int np, double ptmin, double ptmax, double y,
HEJ::RNG & ran
);
double gen_soft_pt(int np, double ptmax, HEJ::RNG & ran);
double gen_parton_pt(
int count, JetParameters const & jet_param, double ptmax, double y,
HEJ::RNG & ran
);
double weight_;
Status status_;
std::array<Particle, 2> incoming_;
std::vector<Particle> outgoing_;
//! Particle decays in the format {outgoing index, decay products}
- std::unordered_map<int, std::vector<Particle>> decays_;
+ std::unordered_map<size_t, std::vector<Particle>> decays_;
};
HEJ::UnclusteredEvent to_UnclusteredEvent(PhaseSpacePoint const & psp);
}
diff --git a/FixedOrderGen/src/PhaseSpacePoint.cc b/FixedOrderGen/src/PhaseSpacePoint.cc
index 31b00b3..e7704b2 100644
--- a/FixedOrderGen/src/PhaseSpacePoint.cc
+++ b/FixedOrderGen/src/PhaseSpacePoint.cc
@@ -1,457 +1,457 @@
#include "PhaseSpacePoint.hh"
#include <random>
#include "HEJ/kinematics.hh"
#include "HEJ/utility.hh"
#include "HEJ/exceptions.hh"
#include "Process.hh"
#include <CLHEP/Random/Randomize.h>
#include <CLHEP/Random/RanluxEngine.h>
using namespace HEJ;
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();
HEJ::UnclusteredEvent to_UnclusteredEvent(PhaseSpacePoint const & psp){
HEJ::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),
HEJ::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(
HEJ::Particle const & p1, HEJ::Particle const & p2
){
return is_parton(p1)
&& p1.type != HEJ::pid::gluon
&& p2.type == HEJ::pid::gluon;
}
}
void PhaseSpacePoint::maybe_turn_to_uno(
double chance,
HEJ::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;
}
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 = sqrt(pt[0]*pt[0]+pt[1]*pt[1]+mass_square);
const double pz=mperp*sinh(y);
const double E=mperp*cosh(y);
return {pt[0], pt[1], pz, E};
}
PhaseSpacePoint::PhaseSpacePoint(
Process const & proc,
JetParameters const & jet_param,
HEJ::PDF & pdf, double E_beam,
double uno_chance,
ParticlesPropMap const & particles_properties,
HEJ::RNG & ran
)
{
assert(proc.njets >= 2);
if(proc.boson
&& particles_properties.find(*(proc.boson))
== particles_properties.end())
throw HEJ::missing_option("Boson "
+std::to_string(*(proc.boson))+" can't be generated: missing properties");
status_ = good;
weight_ = 1;
const int nout = proc.njets + (proc.boson?1:0);
outgoing_.reserve(nout);
const bool is_pure_jets = !proc.boson;
auto partons = gen_LO_partons(
proc.njets, is_pure_jets, jet_param, E_beam, ran
);
for(auto&& p_out: partons) {
outgoing_.emplace_back(Particle{pid::gluon, std::move(p_out)});
}
if(status_ != good) return;
// create boson
if(proc.boson){
const auto & boson_prop = particles_properties.at(*proc.boson);
auto boson(gen_boson(*proc.boson, boson_prop.mass, boson_prop.width, ran));
const auto pos = std::upper_bound(
begin(outgoing_),end(outgoing_),boson,rapidity_less{}
);
outgoing_.insert(pos, std::move(boson));
if(! boson_prop.decays.empty()){
- const int boson_idx = std::distance(begin(outgoing_), pos);
+ const size_t boson_idx = std::distance(begin(outgoing_), pos);
decays_.emplace(
boson_idx,
decay_boson(outgoing_[boson_idx], boson_prop.decays, ran)
);
}
}
// normalisation of momentum-conserving delta function
weight_ *= pow(2*M_PI, 4);
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,
HEJ::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, HEJ::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,
HEJ::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_ = 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,
HEJ::RNG & ran
){
if (np<2) throw std::invalid_argument{"Not enough partons in gen_LO_partons"};
weight_ /= pow(16.*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_ = not_enough_jets;
return {};
}
std::sort(begin(partons), end(partons), rapidity_less{});
return partons;
}
Particle PhaseSpacePoint::gen_boson(
HEJ::ParticleID bosonid, double mass, double width,
HEJ::RNG & ran
){
if(bosonid != HEJ::pid::Higgs)
throw HEJ::not_implemented("Production of boson "+std::to_string(bosonid)
+" not implemented yet.");
// Usual phase space measure
weight_ /= 16.*pow(M_PI, 3);
// Generate a y Gaussian distributed around 0
// TODO: magic number only for Higgs
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))
);
auto p = gen_last_momentum(outgoing_, sH, y);
return Particle{bosonid, std::move(p)};
}
Particle const & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> const & partons
) const{
if(!HEJ::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(!HEJ::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(!HEJ::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(!HEJ::is_parton(partons[last_idx])) return partons[last_idx-1];
return partons[last_idx];
}
void PhaseSpacePoint::reconstruct_incoming(
std::array<HEJ::ParticleID, 2> const & ids,
HEJ::PDF & pdf, double E_beam,
double uf,
HEJ::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 HEJ scale generators currently expect a full event as input,
* so fixing this is not completely trivial
*/
for(size_t i = 0; i < 2; ++i){
if(ids[i] == pid::proton || ids[i] == pid::p_bar){
incoming_[i].type = generate_incoming_id(i, i?xb:xa, uf, pdf, ran);
}
else {
incoming_[i].type = ids[i];
}
}
assert(momentum_conserved(1e-7));
}
namespace {
/// particles are ordered, odd = anti
ParticleID index_to_pid(size_t i){
if(!i) return pid::gluon;
return static_cast<ParticleID>(i%2?(i+1)/2:-i/2);
}
}
HEJ::ParticleID PhaseSpacePoint::generate_incoming_id(
size_t const beam_idx, double const x, double const uf,
HEJ::PDF & pdf, HEJ::RNG & ran
){
std::array<double,11> pdf_wt;
pdf_wt[0] = fabs(pdf.pdfpt(beam_idx,x,uf,pid::gluon));
double pdftot = pdf_wt[0];
for(size_t i = 1; i < pdf_wt.size(); ++i){
pdf_wt[i] = 4./9.*fabs(pdf.pdfpt(beam_idx,x,uf,index_to_pid(i)));
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"};
}
double PhaseSpacePoint::random_normal(
double stddev,
HEJ::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,
HEJ::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(
HEJ::Particle const & parent,
std::vector<Decay> const & decays,
HEJ::RNG & ran
){
const auto channel = select_decay_channel(decays, ran);
if(channel.products.size() != 2){
throw HEJ::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;
}
}
diff --git a/FixedOrderGen/t/h_2j_decay.cc b/FixedOrderGen/t/h_2j_decay.cc
index 3896fb7..e70eba2 100644
--- a/FixedOrderGen/t/h_2j_decay.cc
+++ b/FixedOrderGen/t/h_2j_decay.cc
@@ -1,83 +1,83 @@
#ifdef NDEBUG
#undef NDEBUG
#endif
#include <algorithm>
#include <cmath>
#include <cassert>
#include <iostream>
#include "config.hh"
#include "EventGenerator.hh"
#include "HEJ/Ranlux64.hh"
#include "HEJ/PDF.hh"
#include "HEJ/MatrixElement.hh"
#include "HEJ/utility.hh"
using namespace HEJFOG;
bool pass_dR_cut(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<HEJ::Particle> const & photons
){
constexpr double delta_R_min = 0.7;
for(auto const & jet: jets){
for(auto const & photon: photons){
if(jet.delta_R(photon.p) < delta_R_min) return false;
}
}
return true;
}
int main(){
constexpr double invGeV2_to_pb = 389379292.;
constexpr double xs_ref = 0.00429198; // +- 1.0488e-05
//calculated with rHEJ revision 9570e3809613272ac4b8bf3236279ba23cf64d20
auto config = load_config("config_h_2j_decay.yml");
HEJ::Ranlux64 ran{};
HEJFOG::EventGenerator generator{
config.process,
config.beam,
HEJ::ScaleGenerator{
config.scales.base,
config.scales.factors,
config.scales.max_ratio
},
config.jets,
config.pdf_id,
config.unordered_fraction,
config.particles_properties,
config.Higgs_coupling,
ran
};
double xs = 0., xs_err = 0.;
for (int trials = 0; trials < config.events; ++trials){
auto ev = generator.gen_event();
if(generator.status() != good) continue;
assert(ev.decays().size() == 1);
const auto decay = begin(ev.decays());
- assert(ev.outgoing().size() > static_cast<size_t>(decay->first));
+ assert(ev.outgoing().size() > decay->first);
const auto & the_Higgs = ev.outgoing()[decay->first];
assert(the_Higgs.type == HEJ::pid::Higgs);
assert(decay->second.size() == 2);
auto const & gamma = decay->second;
assert(gamma[0].type == HEJ::pid::photon);
assert(gamma[1].type == HEJ::pid::photon);
assert(HEJ::nearby_ep(gamma[0].p + gamma[1].p, the_Higgs.p, 1e-6));
if(!pass_dR_cut(ev.jets(), gamma)) continue;
ev.central().weight *= invGeV2_to_pb;
ev.central().weight /= config.events;
xs += ev.central().weight;
xs_err += ev.central().weight*ev.central().weight;
}
xs_err = std::sqrt(xs_err);
std::cout << xs_ref << " ~ " << xs << " +- " << xs_err << '\n';
assert(std::abs(xs - xs_ref) < 3*xs_err);
assert(xs_err < 0.012*xs);
}
diff --git a/include/HEJ/Event.hh b/include/HEJ/Event.hh
index 0967bb2..6ad19e5 100644
--- a/include/HEJ/Event.hh
+++ b/include/HEJ/Event.hh
@@ -1,186 +1,186 @@
/** \file
* \brief Declares the Event class and helpers
*
*/
#pragma once
#include <string>
#include <memory>
#include <unordered_map>
#include "HEJ/utility.hh"
#include "HEJ/event_types.hh"
#include "LHEF/LHEF.h"
#include "fastjet/JetDefinition.hh"
#include "fastjet/ClusterSequence.hh"
namespace HEJ{
struct ParameterDescription;
//! Event parameters
struct EventParameters{
double mur; /**< Value of the Renormalisation Scale */
double muf; /**< Value of the Factorisation Scale */
double weight; /**< Event Weight */
//! Optional description
std::shared_ptr<ParameterDescription> description = nullptr;
};
//! Description of event parameters
struct ParameterDescription {
//! Name of central scale choice (e.g. "H_T/2")
std::string scale_name;
//! Actual renormalisation scale divided by central scale
double mur_factor;
//! Actual factorisation scale divided by central scale
double muf_factor;
ParameterDescription() = default;
ParameterDescription(
std::string scale_name, double mur_factor, double muf_factor
):
scale_name{scale_name}, mur_factor{mur_factor}, muf_factor{muf_factor}
{};
};
//! An event before jet clustering
struct UnclusteredEvent{
//! Default Constructor
UnclusteredEvent() = default;
//! Constructor from LesHouches event information
UnclusteredEvent(LHEF::HEPEUP const & hepeup);
std::array<Particle, 2> incoming; /**< Incoming Particles */
std::vector<Particle> outgoing; /**< Outgoing Particles */
//! Particle decays in the format {outgoing index, decay products}
- std::unordered_map<int, std::vector<Particle>> decays;
+ std::unordered_map<size_t, std::vector<Particle>> decays;
//! Central parameter (e.g. scale) choice
EventParameters central;
std::vector<EventParameters> variations; /**< For parameter variation */
};
/** An event with clustered jets
*
* This is the main HEJ 2 event class.
* It contains kinematic information including jet clustering,
* parameter (e.g. scale) settings and the event weight.
*/
class Event{
public:
//! Default Event Constructor
Event() = default;
//! Event Constructor adding jet clustering to an unclustered event
Event(
UnclusteredEvent ev,
fastjet::JetDefinition const & jet_def, double min_jet_pt
);
//! The jets formed by the outgoing partons
std::vector<fastjet::PseudoJet> jets() const;
//! The corresponding event before jet clustering
UnclusteredEvent const & unclustered() const {
return ev_;
}
//! Central parameter choice
EventParameters const & central() const{
return ev_.central;
}
//! Central parameter choice
EventParameters & central(){
return ev_.central;
}
//! Incoming particles
std::array<Particle, 2> const & incoming() const{
return ev_.incoming;
}
//! Outgoing particles
std::vector<Particle> const & outgoing() const{
return ev_.outgoing;
}
//! Particle decays
/**
* The key in the returned map corresponds to the index in the
* vector returned by outgoing()
*/
- std::unordered_map<int, std::vector<Particle>> const & decays() const{
+ std::unordered_map<size_t, std::vector<Particle>> const & decays() const{
return ev_.decays;
}
//! Parameter (scale) variations
std::vector<EventParameters> const & variations() const{
return ev_.variations;
}
//! Parameter (scale) variations
std::vector<EventParameters> & variations(){
return ev_.variations;
}
//! Parameter (scale) variation
/**
* @param i Index of the requested variation
*/
EventParameters const & variations(size_t i) const{
return ev_.variations[i];
}
//! Parameter (scale) variation
/**
* @param i Index of the requested variation
*/
EventParameters & variations(size_t i){
return ev_.variations[i];
}
//! Indices of the jets the outgoing partons belong to
/**
* @param jets Jets to be tested
* @returns A vector containing, for each outgoing parton,
* the index in the vector of jets the considered parton
* belongs to. If the parton is not inside any of the
* passed jets, the corresponding index is set to -1.
*/
std::vector<int> particle_jet_indices(
std::vector<fastjet::PseudoJet> const & jets
) const{
return cs_.particle_jet_indices(jets);
}
//! Jet definition used for clustering
fastjet::JetDefinition const & jet_def() const{
return cs_.jet_def();
}
//! Minimum jet transverse momentum
double min_jet_pt() const{
return min_jet_pt_;
}
//! Event type
event_type::EventType type() const{
return type_;
}
private:
UnclusteredEvent ev_;
fastjet::ClusterSequence cs_;
double min_jet_pt_;
event_type::EventType type_;
};
//! Square of the partonic centre-of-mass energy
double shat(Event const & ev);
//! Convert an event to a LHEF::HEPEUP
LHEF::HEPEUP to_HEPEUP(Event const & event, LHEF::HEPRUP *);
}
diff --git a/include/HEJ/PhaseSpacePoint.hh b/include/HEJ/PhaseSpacePoint.hh
index 90e25b4..dbfc131 100644
--- a/include/HEJ/PhaseSpacePoint.hh
+++ b/include/HEJ/PhaseSpacePoint.hh
@@ -1,148 +1,148 @@
/** \file
* \brief Contains the PhaseSpacePoint Class
*/
#pragma once
#include <vector>
#include "HEJ/utility.hh"
#include "HEJ/config.hh"
#include "HEJ/Event.hh"
#include "HEJ/JetSplitter.hh"
#include "HEJ/RNG.hh"
namespace HEJ{
//! A point in resummation phase space
class PhaseSpacePoint{
public:
//! Default PhaseSpacePoint Constructor
PhaseSpacePoint() = default;
//! PhaseSpacePoint Constructor
/**
* @param ev Clustered Jet Event
* @param conf Configuration parameters
* @param ran Random number generator
*/
PhaseSpacePoint(
Event const & ev,
PhaseSpacePointConfig conf,
HEJ::RNG & ran
);
//! Get phase space point weight
double weight() const{
return weight_;
}
//! Access incoming particles
std::array<Particle, 2> const & incoming() const{
return incoming_;
}
//! Access outgoing particles
std::vector<Particle> const & outgoing() const{
return outgoing_;
}
//! Particle decays
/**
* The key in the returned map corresponds to the index in the
* vector returned by outgoing()
*/
- std::unordered_map<int, std::vector<Particle>> const & decays() const{
+ std::unordered_map<size_t, std::vector<Particle>> const & decays() const{
return decays_;
}
static constexpr int ng_max = 1000; //< maximum number of extra gluons
private:
std::vector<fastjet::PseudoJet> cluster_jets(
std::vector<fastjet::PseudoJet> const & partons
) const;
bool pass_resummation_cuts(
std::vector<fastjet::PseudoJet> const & jets
) const;
bool pass_extremal_cuts(
fastjet::PseudoJet const & ext_parton,
fastjet::PseudoJet const & jet
) const;
int sample_ng(std::vector<fastjet::PseudoJet> const & Born_jets);
int sample_ng_jets(int ng, std::vector<fastjet::PseudoJet> const & Born_jets);
double probability_in_jet(
std::vector<fastjet::PseudoJet> const & Born_jets
) const;
std::vector<fastjet::PseudoJet> gen_non_jet(
int ng_non_jet,
double ptmin, double ptmax
);
void rescale_rapidities(
std::vector<fastjet::PseudoJet> & partons,
double ymin, double ymax
);
std::vector<fastjet::PseudoJet> reshuffle(
std::vector<fastjet::PseudoJet> const & Born_jets,
fastjet::PseudoJet const & q
);
bool jets_ok(
std::vector<fastjet::PseudoJet> const & Born_jets,
std::vector<fastjet::PseudoJet> const & partons
) const;
void reconstruct_incoming(std::array<Particle, 2> const & Born_incoming);
double phase_space_normalisation(
int num_Born_jets,
int num_res_partons
) const;
std::vector<fastjet::PseudoJet> split(
std::vector<fastjet::PseudoJet> const & jets, int ng_jets
);
std::vector<int> distribute_jet_partons(
int ng_jets, std::vector<fastjet::PseudoJet> const & jets
);
std::vector<fastjet::PseudoJet> split(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<int> const & np_in_jet
);
bool split_preserved_jets(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<fastjet::PseudoJet> const & jet_partons
) const;
template<class Particle>
Particle const & most_backward_FKL(
std::vector<Particle> const & partons
) const;
template<class Particle>
Particle const & most_forward_FKL(
std::vector<Particle> const & partons
) const;
template<class Particle>
Particle & most_backward_FKL(std::vector<Particle> & partons) const;
template<class Particle>
Particle & most_forward_FKL(std::vector<Particle> & partons) const;
bool extremal_ok(
std::vector<fastjet::PseudoJet> const & partons
) const;
void copy_AWZH_boson_from(Event const & event);
bool momentum_conserved() const;
bool unob_, unof_;
double weight_;
PhaseSpacePointConfig param_;
std::array<Particle, 2> incoming_;
std::vector<Particle> outgoing_;
//! \internal Particle decays in the format {outgoing index, decay products}
- std::unordered_map<int, std::vector<Particle>> decays_;
+ std::unordered_map<size_t, std::vector<Particle>> decays_;
std::reference_wrapper<HEJ::RNG> ran_;
};
}
diff --git a/src/Event.cc b/src/Event.cc
index 4427004..f098930 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -1,343 +1,343 @@
#include "HEJ/Event.hh"
#include "HEJ/utility.hh"
namespace HEJ{
namespace{
constexpr int status_in = -1;
constexpr int status_decayed = 2;
constexpr int status_out = 1;
// helper functions to determine event type
// check if there is at most one photon, W, H, Z in the final state
// and all the rest are quarks or gluons
bool final_state_ok(std::vector<Particle> const & outgoing){
bool has_AWZH_boson = false;
for(auto const & out: outgoing){
if(is_AWZH_boson(out.type)){
if(has_AWZH_boson) return false;
has_AWZH_boson = true;
}
else if(! is_parton(out.type)) return false;
}
return true;
}
template<class Iterator>
Iterator remove_AWZH(Iterator begin, Iterator end){
return std::remove_if(
begin, end, [](Particle const & p){return is_AWZH_boson(p);}
);
}
template<class Iterator>
bool valid_outgoing(Iterator begin, Iterator end){
return std::distance(begin, end) >= 2
&& std::is_sorted(begin, end, rapidity_less{})
&& std::count_if(
begin, end, [](Particle const & s){return is_AWZH_boson(s);}
) < 2;
}
// Note that this changes the outgoing range!
template<class ConstIterator, class Iterator>
bool is_FKL(
ConstIterator begin_incoming, ConstIterator end_incoming,
Iterator begin_outgoing, Iterator end_outgoing
){
assert(std::distance(begin_incoming, end_incoming) == 2);
assert(std::distance(begin_outgoing, end_outgoing) >= 2);
// One photon, W, H, Z in the final state is allowed.
// Remove it for remaining tests,
end_outgoing = remove_AWZH(begin_outgoing, end_outgoing);
// Test if this is a standard FKL configuration.
return
(begin_incoming->type == begin_outgoing->type)
&& ((end_incoming-1)->type == (end_outgoing-1)->type)
&& std::all_of(
begin_outgoing + 1, end_outgoing - 1,
[](Particle const & p){ return p.type == pid::gluon; }
);
}
bool is_FKL(
std::array<Particle, 2> const & incoming,
std::vector<Particle> outgoing
){
assert(std::is_sorted(begin(incoming), end(incoming), pz_less{}));
assert(valid_outgoing(begin(outgoing), end(outgoing)));
return is_FKL(
begin(incoming), end(incoming),
begin(outgoing), end(outgoing)
);
}
bool has_2_jets(Event const & event){
return event.jets().size() >= 2;
}
/**
* \brief Checks whether event is unordered backwards
* @param ev Event
* @returns Is Event Unordered Backwards
*
* Checks there is more than 3 constuents in the final state
* Checks there is more than 3 jets
* Checks the most backwards parton is a gluon
* Checks the most forwards jet is not a gluon
* Checks the rest of the event is FKL
* Checks the second most backwards is not a different boson
* Checks the unordered gluon actually forms a jet
*/
bool is_unordered_backward(Event const & ev){
auto const & in = ev.incoming();
auto const & out = ev.outgoing();
assert(std::is_sorted(begin(in), end(in), pz_less{}));
assert(valid_outgoing(begin(out), end(out)));
if(out.size() < 3) return false;
if(ev.jets().size() < 3) return false;
if(in.front().type == pid::gluon) return false;
if(out.front().type != pid::gluon) return false;
// When skipping the unordered emission
// the remainder should be a regular FKL event,
// except that the (new) first outgoing particle must not be a A,W,Z,H.
const auto FKL_begin = next(begin(out));
if(is_AWZH_boson(*FKL_begin)) return false;
if(!is_FKL(in, {FKL_begin, end(out)})) return false;
// check that the unordered gluon forms an extra jet
const auto jets = sorted_by_rapidity(ev.jets());
const auto indices = ev.particle_jet_indices({jets.front()});
return indices[0] >= 0 && indices[1] == -1;
}
/**
* \brief Checks for a forward unordered gluon emission
* @param ev Event
* @returns Is the event a forward unordered emission
*
* \see is_unordered_backward
*/
bool is_unordered_forward(Event const & ev){
auto const & in = ev.incoming();
auto const & out = ev.outgoing();
assert(std::is_sorted(begin(in), end(in), pz_less{}));
assert(valid_outgoing(begin(out), end(out)));
if(out.size() < 3) return false;
if(ev.jets().size() < 3) return false;
if(in.back().type == pid::gluon) return false;
if(out.back().type != pid::gluon) return false;
// When skipping the unordered emission
// the remainder should be a regular FKL event,
// except that the (new) last outgoing particle must not be a A,W,Z,H.
const auto FKL_end = prev(end(out));
if(is_AWZH_boson(*prev(FKL_end))) return false;
if(!is_FKL(in, {begin(out), FKL_end})) return false;
// check that the unordered gluon forms an extra jet
const auto jets = sorted_by_rapidity(ev.jets());
const auto indices = ev.particle_jet_indices({jets.back()});
return indices.back() >= 0 && indices[indices.size()-2] == -1;
}
using event_type::EventType;
EventType classify(Event const & ev){
if(! final_state_ok(ev.outgoing())) return EventType::bad_final_state;
if(! has_2_jets(ev)) return EventType::no_2_jets;
if(is_FKL(ev.incoming(), ev.outgoing())) return EventType::FKL;
if(is_unordered_backward(ev)){
return EventType::unordered_backward;
}
if(is_unordered_forward(ev)){
return EventType::unordered_forward;
}
return EventType::nonHEJ;
}
Particle extract_particle(LHEF::HEPEUP const & hepeup, int i){
return Particle{
static_cast<ParticleID>(hepeup.IDUP[i]),
fastjet::PseudoJet{
hepeup.PUP[i][0], hepeup.PUP[i][1],
hepeup.PUP[i][2], hepeup.PUP[i][3]
}
};
}
bool is_decay_product(std::pair<int, int> const & mothers){
if(mothers.first == 0) return false;
return mothers.second == 0 || mothers.first == mothers.second;
}
}
UnclusteredEvent::UnclusteredEvent(LHEF::HEPEUP const & hepeup):
central(EventParameters{
hepeup.scales.mur, hepeup.scales.muf, hepeup.weight()
})
{
size_t in_idx = 0;
for (int i = 0; i < hepeup.NUP; ++i) {
// skip decay products
// we will add them later on, but we have to ensure that
// the decayed particle is added before
if(is_decay_product(hepeup.MOTHUP[i])) continue;
auto particle = extract_particle(hepeup, i);
// needed to identify mother particles for decay products
particle.p.set_user_index(i+1);
if(hepeup.ISTUP[i] == status_in){
if(in_idx > incoming.size()) {
throw std::invalid_argument{
"Event has too many incoming particles"
};
}
incoming[in_idx++] = std::move(particle);
}
else outgoing.emplace_back(std::move(particle));
}
std::sort(
begin(incoming), end(incoming),
[](Particle o1, Particle o2){return o1.p.pz()<o2.p.pz();}
);
std::sort(begin(outgoing), end(outgoing), rapidity_less{});
// add decay products
for (int i = 0; i < hepeup.NUP; ++i) {
if(!is_decay_product(hepeup.MOTHUP[i])) continue;
const int mother_id = hepeup.MOTHUP[i].first;
const auto mother = std::find_if(
begin(outgoing), end(outgoing),
[mother_id](Particle const & particle){
return particle.p.user_index() == mother_id;
}
);
if(mother == end(outgoing)){
throw std::invalid_argument{"invalid decay product parent"};
}
const int mother_idx = std::distance(begin(outgoing), mother);
assert(mother_idx >= 0);
decays[mother_idx].emplace_back(extract_particle(hepeup, i));
}
}
Event::Event(
UnclusteredEvent ev,
fastjet::JetDefinition const & jet_def, double min_jet_pt
):
ev_{std::move(ev)},
cs_{to_PseudoJet(filter_partons(ev_.outgoing)), jet_def},
min_jet_pt_{min_jet_pt}
{
type_ = classify(*this);
}
std::vector<fastjet::PseudoJet> Event::jets() const{
return cs_.inclusive_jets(min_jet_pt_);
}
/**
* \brief Returns the invarient mass of the event
* @param ev Event
* @returns s hat
*
* Makes use of the FastJet PseudoJet function m2().
* Applies this function to the sum of the incoming partons.
*/
double shat(Event const & ev){
return (ev.incoming()[0].p + ev.incoming()[1].p).m2();
}
namespace{
// colour flow according to Les Houches standard
// TODO: stub
std::vector<std::pair<int, int>> colour_flow(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing
){
std::vector<std::pair<int, int>> result(
incoming.size() + outgoing.size()
);
for(auto & col: result){
col = std::make_pair(-1, -1);
}
return result;
}
}
LHEF::HEPEUP to_HEPEUP(Event const & event, LHEF::HEPRUP * heprup){
LHEF::HEPEUP result;
result.heprup = heprup;
result.weights = {{event.central().weight, nullptr}};
for(auto const & var: event.variations()){
result.weights.emplace_back(var.weight, nullptr);
}
size_t num_particles = event.incoming().size() + event.outgoing().size();
for(auto const & decay: event.decays()) num_particles += decay.second.size();
result.NUP = num_particles;
// the following entries are pretty much meaningless
result.IDPRUP = event.type()+1; // event ID
result.AQEDUP = 1./128.; // alpha_EW
//result.AQCDUP = 0.118 // alpha_QCD
// end meaningless part
result.XWGTUP = event.central().weight;
result.SCALUP = event.central().muf;
result.scales.muf = event.central().muf;
result.scales.mur = event.central().mur;
result.scales.SCALUP = event.central().muf;
result.pdfinfo.p1 = event.incoming().front().type;
result.pdfinfo.p2 = event.incoming().back().type;
result.pdfinfo.scale = event.central().muf;
for(Particle const & in: event.incoming()){
result.IDUP.emplace_back(in.type);
result.ISTUP.emplace_back(status_in);
result.PUP.push_back({in.p[0], in.p[1], in.p[2], in.p[3], in.p.m()});
result.MOTHUP.emplace_back(0, 0);
}
for(size_t i = 0; i < event.outgoing().size(); ++i){
Particle const & out = event.outgoing()[i];
result.IDUP.emplace_back(out.type);
const int status = event.decays().count(i)?status_decayed:status_out;
result.ISTUP.emplace_back(status);
result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
result.MOTHUP.emplace_back(1, 2);
}
result.ICOLUP = colour_flow(
event.incoming(), filter_partons(event.outgoing())
);
if(result.ICOLUP.size() < num_particles){
const size_t AWZH_boson_idx = std::find_if(
begin(event.outgoing()), end(event.outgoing()),
[](Particle const & s){ return is_AWZH_boson(s); }
) - begin(event.outgoing()) + event.incoming().size();
assert(AWZH_boson_idx <= result.ICOLUP.size());
result.ICOLUP.insert(
begin(result.ICOLUP) + AWZH_boson_idx,
std::make_pair(0,0)
);
}
for(auto const & decay: event.decays()){
for(auto const out: decay.second){
result.IDUP.emplace_back(out.type);
result.ISTUP.emplace_back(status_out);
result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
- const int mother_idx = 1 + event.incoming().size() + decay.first;
+ const size_t mother_idx = 1 + event.incoming().size() + decay.first;
result.MOTHUP.emplace_back(mother_idx, mother_idx);
result.ICOLUP.emplace_back(0,0);
}
}
assert(result.ICOLUP.size() == num_particles);
static constexpr double unknown_spin = 9.; //per Les Houches accord
result.VTIMUP = std::vector<double>(num_particles, unknown_spin);
result.SPINUP = result.VTIMUP;
return result;
}
}
diff --git a/src/PhaseSpacePoint.cc b/src/PhaseSpacePoint.cc
index c3047e3..c243ae2 100644
--- a/src/PhaseSpacePoint.cc
+++ b/src/PhaseSpacePoint.cc
@@ -1,537 +1,539 @@
#include "HEJ/PhaseSpacePoint.hh"
#include <random>
#include <CLHEP/Random/Randomize.h>
#include <CLHEP/Random/RanluxEngine.h>
#include "HEJ/Constants.hh"
#include "HEJ/resummation_jet_momenta.hh"
#include "HEJ/Jacobian.hh"
#include "HEJ/uno.hh"
#include "HEJ/utility.hh"
#include "HEJ/kinematics.hh"
namespace HEJ{
namespace {
constexpr int max_jet_user_idx = PhaseSpacePoint::ng_max;
bool is_nonjet_parton(fastjet::PseudoJet const & parton){
assert(parton.user_index() != -1);
return parton.user_index() > max_jet_user_idx;
}
bool is_jet_parton(fastjet::PseudoJet const & parton){
assert(parton.user_index() != -1);
return parton.user_index() <= max_jet_user_idx;
}
// user indices for partons with extremal rapidity
constexpr int unob_idx = -5;
constexpr int unof_idx = -4;
constexpr int backward_FKL_idx = -3;
constexpr int forward_FKL_idx = -2;
}
namespace {
double estimate_ng_mean(std::vector<fastjet::PseudoJet> const & Born_jets){
const double delta_y =
Born_jets.back().rapidity() - Born_jets.front().rapidity();
assert(delta_y > 0);
// Formula derived from fit in arXiv:1805.04446 (see Fig. 2)
return 0.975052*delta_y;
}
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::cluster_jets(
std::vector<fastjet::PseudoJet> const & partons
) const{
fastjet::ClusterSequence cs(partons, param_.jet_param.def);
return cs.inclusive_jets(param_.jet_param.min_pt);
}
bool PhaseSpacePoint::pass_resummation_cuts(
std::vector<fastjet::PseudoJet> const & jets
) const{
return cluster_jets(jets).size() == jets.size();
}
int PhaseSpacePoint::sample_ng(std::vector<fastjet::PseudoJet> const & Born_jets){
const double ng_mean = estimate_ng_mean(Born_jets);
std::poisson_distribution<int> dist(ng_mean);
const int ng = dist(ran_.get());
assert(ng >= 0);
assert(ng < ng_max);
weight_ *= std::tgamma(ng + 1)*std::exp(ng_mean)*std::pow(ng_mean, -ng);
return ng;
}
void PhaseSpacePoint::copy_AWZH_boson_from(Event const & event){
auto const & from = event.outgoing();
const auto AWZH_boson = std::find_if(
begin(from), end(from),
[](Particle const & p){ return is_AWZH_boson(p); }
);
if(AWZH_boson == end(from)) return;
auto insertion_point = std::lower_bound(
begin(outgoing_), end(outgoing_), *AWZH_boson, rapidity_less{}
);
outgoing_.insert(insertion_point, *AWZH_boson);
// copy decay products
const int idx = std::distance(begin(from), AWZH_boson);
+ assert(idx >= 0);
const auto decay_it = event.decays().find(idx);
if(decay_it != end(event.decays())){
const int new_idx = std::distance(begin(outgoing_), insertion_point);
+ assert(new_idx >= 0);
assert(outgoing_[new_idx].type == AWZH_boson->type);
decays_.emplace(new_idx, decay_it->second);
}
assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
}
PhaseSpacePoint::PhaseSpacePoint(
Event const & ev, PhaseSpacePointConfig conf, HEJ::RNG & ran
):
unob_{has_unob_gluon(ev.incoming(), ev.outgoing())},
unof_{!unob_ && has_unof_gluon(ev.incoming(), ev.outgoing())},
param_{std::move(conf)},
ran_{ran}
{
weight_ = 1;
const auto Born_jets = sorted_by_rapidity(ev.jets());
const int ng = sample_ng(Born_jets);
weight_ /= std::tgamma(ng + 1);
const int ng_jets = sample_ng_jets(ng, Born_jets);
std::vector<fastjet::PseudoJet> out_partons = gen_non_jet(
ng - ng_jets, CMINPT, param_.jet_param.min_pt
);
{
const auto qperp = std::accumulate(
begin(out_partons), end(out_partons),
fastjet::PseudoJet{}
);
const auto jets = reshuffle(Born_jets, qperp);
if(weight_ == 0.) return;
if(! pass_resummation_cuts(jets)){
weight_ = 0.;
return;
}
std::vector<fastjet::PseudoJet> jet_partons = split(jets, ng_jets);
if(weight_ == 0.) return;
rescale_rapidities(
out_partons,
most_backward_FKL(jet_partons).rapidity(),
most_forward_FKL(jet_partons).rapidity()
);
if(! cluster_jets(out_partons).empty()){
weight_ = 0.;
return;
}
std::sort(begin(out_partons), end(out_partons), rapidity_less{});
assert(
std::is_sorted(begin(jet_partons), end(jet_partons), rapidity_less{})
);
const auto first_jet_parton = out_partons.insert(
end(out_partons), begin(jet_partons), end(jet_partons)
);
std::inplace_merge(
begin(out_partons), first_jet_parton, end(out_partons), rapidity_less{}
);
}
if(! jets_ok(Born_jets, out_partons)){
weight_ = 0.;
return;
}
weight_ *= phase_space_normalisation(Born_jets.size(), out_partons.size());
outgoing_.reserve(out_partons.size() + 1); // one slot for possible A, W, Z, H
for(auto & p: out_partons){
outgoing_.emplace_back(Particle{pid::gluon, std::move(p)});
}
most_backward_FKL(outgoing_).type = ev.incoming().front().type;
most_forward_FKL(outgoing_).type = ev.incoming().back().type;
copy_AWZH_boson_from(ev);
assert(!outgoing_.empty());
reconstruct_incoming(ev.incoming());
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_non_jet(
int count, double ptmin, double ptmax
){
// heuristic parameters for pt sampling
const double ptpar = 1.3 + count/5.;
const double temp1 = atan((ptmax - ptmin)/ptpar);
std::vector<fastjet::PseudoJet> partons(count);
for(size_t i = 0; i < (size_t) count; ++i){
const double r1 = ran_.get().flat();
const double pt = ptmin + ptpar*tan(r1*temp1);
const double temp2 = cos(r1*temp1);
const double phi = 2*M_PI*ran_.get().flat();
weight_ *= 2.0*M_PI*pt*ptpar*temp1/(temp2*temp2);
// we don't know the allowed rapidity span yet,
// set a random value to be rescaled later on
const double y = ran_.get().flat();
partons[i].reset_PtYPhiM(pt, y, phi);
// Set user index higher than any jet-parton index
// in order to assert that these are not inside jets
partons[i].set_user_index(i + 1 + ng_max);
assert(ptmin-1e-5 <= partons[i].pt() && partons[i].pt() <= ptmax+1e-5);
}
assert(std::all_of(partons.cbegin(), partons.cend(), is_nonjet_parton));
return partons;
}
void PhaseSpacePoint::rescale_rapidities(
std::vector<fastjet::PseudoJet> & partons,
double ymin, double ymax
){
constexpr double ep = 1e-7;
for(auto & parton: partons){
assert(0 <= parton.rapidity() && parton.rapidity() <= 1);
const double dy = ymax - ymin - 2*ep;
const double y = ymin + ep + dy*parton.rapidity();
parton.reset_momentum_PtYPhiM(parton.pt(), y, parton.phi());
weight_ *= dy;
assert(ymin <= parton.rapidity() && parton.rapidity() <= ymax);
}
}
namespace {
template<typename T, typename... Rest>
auto min(T const & a, T const & b, Rest&&... r) {
using std::min;
return min(a, min(b, std::forward<Rest>(r)...));
}
}
double PhaseSpacePoint::probability_in_jet(
std::vector<fastjet::PseudoJet> const & Born_jets
) const{
assert(std::is_sorted(begin(Born_jets), end(Born_jets), rapidity_less{}));
assert(Born_jets.size() >= 2);
const double dy =
Born_jets.back().rapidity() - Born_jets.front().rapidity();
const double R = param_.jet_param.def.R();
const int njets = Born_jets.size();
const double p_J_y_large = (njets-1)*R*R/(2.*dy);
const double p_J_y0 = njets*R/M_PI;
return min(p_J_y_large, p_J_y0, 1.);
}
int PhaseSpacePoint::sample_ng_jets(
int ng, std::vector<fastjet::PseudoJet> const & Born_jets
){
const double p_J = probability_in_jet(Born_jets);
std::binomial_distribution<> bin_dist(ng, p_J);
const int ng_J = bin_dist(ran_.get());
weight_ *= std::pow(p_J, -ng_J)*std::pow(1 - p_J, ng_J - ng);
return ng_J;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::reshuffle(
std::vector<fastjet::PseudoJet> const & Born_jets,
fastjet::PseudoJet const & q
){
if(q == fastjet::PseudoJet{0, 0, 0, 0}) return Born_jets;
const auto jets = resummation_jet_momenta(Born_jets, q);
if(jets.empty()){
weight_ = 0;
return {};
}
// additional Jacobian to ensure Born integration over delta gives 1
weight_ *= Jacobian(Born_jets, q);
return jets;
}
std::vector<int> PhaseSpacePoint::distribute_jet_partons(
int ng_jets, std::vector<fastjet::PseudoJet> const & jets
){
size_t first_valid_jet = 0;
size_t num_valid_jets = jets.size();
const double R_eff = 5./3.*param_.jet_param.def.R();
// if there is an unordered jet too far away from the FKL jets
// then extra gluon constituents of the unordered jet would
// violate the FKL rapidity ordering
if(unob_ && jets[0].delta_R(jets[1]) > R_eff){
++first_valid_jet;
--num_valid_jets;
}
else if(unof_ && jets[jets.size()-1].delta_R(jets[jets.size()-2]) > R_eff){
--num_valid_jets;
}
std::vector<int> np(jets.size(), 1);
for(int i = 0; i < ng_jets; ++i){
++np[first_valid_jet + ran_.get().flat() * num_valid_jets];
}
weight_ *= std::pow(num_valid_jets, ng_jets);
return np;
}
#ifndef NDEBUG
namespace{
bool tagged_FKL_backward(
std::vector<fastjet::PseudoJet> const & jet_partons
){
return std::find_if(
begin(jet_partons), end(jet_partons),
[](fastjet::PseudoJet const & p){
return p.user_index() == backward_FKL_idx;
}
) != end(jet_partons);
}
bool tagged_FKL_forward(
std::vector<fastjet::PseudoJet> const & jet_partons
){
// the most forward FKL parton is most likely near the end of jet_partons;
// start search from there
return std::find_if(
jet_partons.rbegin(), jet_partons.rend(),
[](fastjet::PseudoJet const & p){
return p.user_index() == forward_FKL_idx;
}
) != jet_partons.rend();
}
bool tagged_FKL_extremal(
std::vector<fastjet::PseudoJet> const & jet_partons
){
return tagged_FKL_backward(jet_partons) && tagged_FKL_forward(jet_partons);
}
} // namespace anonymous
#endif
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
std::vector<fastjet::PseudoJet> const & jets,
int ng_jets
){
return split(jets, distribute_jet_partons(ng_jets, jets));
}
bool PhaseSpacePoint::pass_extremal_cuts(
fastjet::PseudoJet const & ext_parton,
fastjet::PseudoJet const & jet
) const{
if(ext_parton.pt() < param_.min_extparton_pt) return false;
return (ext_parton - jet).pt()/jet.pt() < param_.max_ext_soft_pt_fraction;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<int> const & np
){
assert(! jets.empty());
assert(jets.size() == np.size());
assert(pass_resummation_cuts(jets));
const size_t most_backward_FKL_idx = 0 + unob_;
const size_t most_forward_FKL_idx = jets.size() - 1 - unof_;
const auto & jet = param_.jet_param;
const JetSplitter jet_splitter{jet.def, jet.min_pt, ran_};
std::vector<fastjet::PseudoJet> jet_partons;
// randomly distribute jet gluons among jets
for(size_t i = 0; i < jets.size(); ++i){
auto split_res = jet_splitter.split(jets[i], np[i]);
weight_ *= split_res.weight;
if(weight_ == 0) return {};
assert(
std::all_of(
begin(split_res.constituents), end(split_res.constituents),
is_jet_parton
)
);
const auto first_new_parton = jet_partons.insert(
end(jet_partons),
begin(split_res.constituents), end(split_res.constituents)
);
// mark uno and extremal FKL emissions here so we can check
// their position once all emissions are generated
auto extremal = end(jet_partons);
if((unob_ && i == 0) || i == most_backward_FKL_idx){
// unordered or FKL backward emission
extremal = std::min_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(
(i == most_backward_FKL_idx)?backward_FKL_idx:unob_idx
);
}
else if((unof_ && i == jets.size() - 1) || i == most_forward_FKL_idx){
// unordered or FKL forward emission
extremal = std::max_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(
(i == most_forward_FKL_idx)?forward_FKL_idx:unof_idx
);
}
if(
extremal != end(jet_partons)
&& !pass_extremal_cuts(*extremal, jets[i])
){
weight_ = 0;
return {};
}
}
assert(tagged_FKL_extremal(jet_partons));
std::sort(begin(jet_partons), end(jet_partons), rapidity_less{});
if(
!extremal_ok(jet_partons)
|| !split_preserved_jets(jets, jet_partons)
){
weight_ = 0.;
return {};
}
return jet_partons;
}
bool PhaseSpacePoint::extremal_ok(
std::vector<fastjet::PseudoJet> const & partons
) const{
assert(std::is_sorted(begin(partons), end(partons), rapidity_less{}));
if(unob_ && partons.front().user_index() != unob_idx) return false;
if(unof_ && partons.back().user_index() != unof_idx) return false;
return
most_backward_FKL(partons).user_index() == backward_FKL_idx
&& most_forward_FKL(partons).user_index() == forward_FKL_idx;
}
bool PhaseSpacePoint::split_preserved_jets(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<fastjet::PseudoJet> const & jet_partons
) const{
assert(std::is_sorted(begin(jets), end(jets), rapidity_less{}));
const auto split_jets = sorted_by_rapidity(cluster_jets(jet_partons));
// this can happen if two overlapping jets
// are both split into more than one parton
if(split_jets.size() != jets.size()) return false;
for(size_t i = 0; i < split_jets.size(); ++i){
// this can happen if there are two overlapping jets
// and a parton is assigned to the "wrong" jet
if(!nearby_ep(jets[i].rapidity(), split_jets[i].rapidity(), 1e-2)){
return false;
}
}
return true;
}
template<class Particle>
Particle const & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> const & partons
) const{
return partons[0 + unob_];
}
template<class Particle>
Particle const & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> const & partons
) const{
const size_t idx = partons.size() - 1 - unof_;
assert(idx < partons.size());
return partons[idx];
}
template<class Particle>
Particle & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> & partons
) const{
return partons[0 + unob_];
}
template<class Particle>
Particle & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> & partons
) const{
const size_t idx = partons.size() - 1 - unof_;
assert(idx < partons.size());
return partons[idx];
}
namespace {
bool contains_idx(
fastjet::PseudoJet const & jet, fastjet::PseudoJet const & parton
){
auto const & constituents = jet.constituents();
const int idx = parton.user_index();
return std::find_if(
begin(constituents), end(constituents),
[idx](fastjet::PseudoJet const & con){return con.user_index() == idx;}
) != end(constituents);
}
}
/**
* final jet test:
* - number of jets must match Born kinematics
* - no partons designated as nonjet may end up inside jets
* - all other outgoing partons *must* end up inside jets
* - the extremal (in rapidity) partons must be inside the extremal jets
* - rapidities must be the same (by construction)
*/
bool PhaseSpacePoint::jets_ok(
std::vector<fastjet::PseudoJet> const & Born_jets,
std::vector<fastjet::PseudoJet> const & partons
) const{
fastjet::ClusterSequence cs(partons, param_.jet_param.def);
const auto jets = sorted_by_rapidity(cs.inclusive_jets(param_.jet_param.min_pt));
if(jets.size() != Born_jets.size()) return false;
int in_jet = 0;
for(size_t i = 0; i < jets.size(); ++i){
assert(jets[i].has_constituents());
for(auto && parton: jets[i].constituents()){
if(is_nonjet_parton(parton)) return false;
}
in_jet += jets[i].constituents().size();
}
const int expect_in_jet = std::count_if(
partons.cbegin(), partons.cend(), is_jet_parton
);
if(in_jet != expect_in_jet) return false;
// note that PseudoJet::contains does not work here
if(! (
contains_idx(most_backward_FKL(jets), most_backward_FKL(partons))
&& contains_idx(most_forward_FKL(jets), most_forward_FKL(partons))
)) return false;
if(unob_ && !contains_idx(jets.front(), partons.front())) return false;
if(unof_ && !contains_idx(jets.back(), partons.back())) return false;
for(size_t i = 0; i < jets.size(); ++i){
assert(nearby_ep(jets[i].rapidity(), Born_jets[i].rapidity(), 1e-2));
}
return true;
}
void PhaseSpacePoint::reconstruct_incoming(
std::array<Particle, 2> const & Born_incoming
){
std::tie(incoming_[0].p, incoming_[1].p) = incoming_momenta(outgoing_);
for(size_t i = 0; i < incoming_.size(); ++i){
incoming_[i].type = Born_incoming[i].type;
}
assert(momentum_conserved());
}
double PhaseSpacePoint::phase_space_normalisation(
int num_Born_jets, int num_out_partons
) const{
return pow(16*pow(M_PI,3), num_Born_jets - num_out_partons);
}
bool PhaseSpacePoint::momentum_conserved() const{
fastjet::PseudoJet diff;
for(auto const & in: incoming()) diff += in.p;
const double norm = diff.E();
for(auto const & out: outgoing()) diff -= out.p;
return nearby(diff, fastjet::PseudoJet{}, norm);
}
} //namespace HEJ

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