diff --git a/src/PhaseSpacePoint.cc b/src/PhaseSpacePoint.cc
index b631f00..7dd83df 100644
--- a/src/PhaseSpacePoint.cc
+++ b/src/PhaseSpacePoint.cc
@@ -1,977 +1,977 @@
/**
* \authors The HEJ collaboration (see AUTHORS for details)
* \date 2019-2020
* \copyright GPLv2 or later
*/
#include "HEJ/PhaseSpacePoint.hh"
#include <algorithm>
#include <cassert>
#include <cmath>
#include <cstdlib>
#include <functional>
#include <iterator>
#include <limits>
#include <numeric>
#include <random>
#include <tuple>
#include "fastjet/ClusterSequence.hh"
#include "fastjet/JetDefinition.hh"
#include "HEJ/Constants.hh"
#include "HEJ/Event.hh"
#include "HEJ/JetSplitter.hh"
#include "HEJ/PDG_codes.hh"
#include "HEJ/RNG.hh"
#include "HEJ/event_types.hh"
#include "HEJ/kinematics.hh"
#include "HEJ/resummation_jet.hh"
#include "HEJ/utility.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;
}
namespace user_idx {
//! user indices for partons with extremal rapidity
enum ID: int {
qqbar_mid1 = -9,
qqbar_mid2 = -8,
qqbarb = -7,
qqbarf = -6,
unob = -5,
unof = -4,
backward_fkl = -3,
forward_fkl = -2,
};
} // namespace user_idx
using UID = user_idx::ID;
double phase_space_normalisation(
int num_Born_jets, int num_out_partons
){
return std::pow(16.*std::pow(M_PI,3), num_Born_jets - num_out_partons);
}
} // namespace
Event::EventData to_EventData(PhaseSpacePoint psp){
Event::EventData result;
result.incoming = std::move(psp).incoming_; // NOLINT(bugprone-use-after-move)
result.outgoing = std::move(psp).outgoing_; // NOLINT(bugprone-use-after-move)
// 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);
static_assert(
std::numeric_limits<double>::has_quiet_NaN,
"no quiet NaN for double"
);
constexpr double nan = std::numeric_limits<double>::quiet_NaN();
result.decays = std::move(psp).decays_; // NOLINT(bugprone-use-after-move)
result.parameters.central = {nan, nan, psp.weight()}; // NOLINT(bugprone-use-after-move)
return result;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::cluster_jets(
std::vector<fastjet::PseudoJet> const & partons
) const{
fastjet::ClusterSequence cs(partons, param_.jet_param.def);
return sorted_by_rapidity(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();
}
namespace {
// find iterators to central qqbar emission
auto get_central_qqbar(Event const & ev) {
// find born quarks (ignore extremal partons)
auto const firstquark = std::find_if(
std::next(ev.begin_partons()), std::prev(ev.end_partons(), 2),
[](Particle const & s){ return (is_anyquark(s)); }
);
// assert that it is a q-q_bar pair.
assert(std::distance(firstquark, ev.end_partons()) != 2);
assert(
( is_quark(*firstquark) && is_antiquark(*std::next(firstquark)) )
|| ( is_antiquark(*firstquark) && is_quark(*std::next(firstquark)) )
);
return std::make_pair(firstquark, std::next(firstquark));
}
//! returns index of most backward q-qbar jet
template<class Iterator>
int get_back_quark_jet(Event const & ev, Iterator firstquark){
// find jets at FO corresponding to the quarks
// technically this isn't necessary for LO
std::vector<int> const born_indices{ ev.particle_jet_indices() };
const auto firstquark_idx = std::distance(ev.begin_partons(), firstquark);
int const firstjet_idx = born_indices[firstquark_idx];
assert(firstjet_idx>0);
assert( born_indices[firstquark_idx+1] == firstjet_idx+1 );
return firstjet_idx;
}
//! returns index of most backward q-qbar jet
int getBackQuarkJet(Event const & ev){
const auto firstquark = get_central_qqbar(ev).first;
return get_back_quark_jet(ev, firstquark);
}
} // namespace
double PhaseSpacePoint::estimate_emission_rapidity_range(
Event const & ev
) const {
assert(std::is_sorted(begin(ev.jets()), end(ev.jets()), rapidity_less{}));
const double ymin = is_backward_g_to_h(ev)?
ev.outgoing().front().rapidity():
most_backward_FKL(ev.jets()).rapidity();
const double ymax = is_forward_g_to_h(ev)?
ev.outgoing().back().rapidity():
most_forward_FKL(ev.jets()).rapidity();
double delta_y = ymax - ymin;
// neglect tiny probability for emission between central qqbar pair
if(ev.type() == event_type::central_qqbar) {
const int qjet = getBackQuarkJet(ev);
delta_y -= ev.jets()[qjet+1].rapidity() - ev.jets()[qjet].rapidity();
}
assert(delta_y >= 0);
return delta_y;
}
double PhaseSpacePoint::estimate_ng_mean(Event const & ev) const {
// Formula derived from fit in arXiv:1805.04446 (see Fig. 2)
constexpr double GLUONS_PER_RAPIDITY = 0.975052;
return GLUONS_PER_RAPIDITY*estimate_emission_rapidity_range(ev);
}
int PhaseSpacePoint::sample_ng(Event const & event, RNG & ran){
const double ng_mean = estimate_ng_mean(event);
std::poisson_distribution<int> dist(ng_mean);
const int ng = dist(ran);
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::boost_AWZH_bosons_from(
std::vector<fastjet::PseudoJet> const & boosted_bosons, Event const & event
){
auto const & from = event.outgoing();
auto find_AWZH = [](Particle const & p){ return is_AWZH_boson(p); };
size_t boosted_idx = 0;
for(
auto original_boson = std::find_if(begin(from), end(from), find_AWZH);
original_boson != end(from);
original_boson = std::find_if(++original_boson, end(from), find_AWZH),
++boosted_idx
){
auto insertion_point = std::lower_bound(
begin(outgoing_), end(outgoing_), *original_boson, rapidity_less{}
);
// copy AWZH particle
const int new_idx = std::distance(begin(outgoing_), insertion_point);
assert(new_idx >= 0); // insert invalidates distance
- assert(outgoing_[new_idx].type == original_boson->type);
outgoing_.insert(insertion_point,
{original_boson->type, boosted_bosons[boosted_idx], original_boson->colour}
);
+ assert(outgoing_[new_idx].type == original_boson->type);
assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
// copy & boost decay products
const int idx = std::distance(begin(from), original_boson);
assert(idx >= 0);
const auto decay_it = event.decays().find(idx);
if(decay_it != end(event.decays())){
auto decayparticles = decay_it->second;
// change the momenta of the decay products.
fastjet::PseudoJet sum;
for(auto & particle: decayparticles){
auto & p = particle.p;
// boost _to_ rest frame of input boson
p.unboost(original_boson->p);
// then boost _from_ rest frame of shuffled boson
p.boost(boosted_bosons[boosted_idx]);
if(p.E() < std::abs(p.pz())){
throw std::underflow_error("Reshuffled decay with E<|pz|");
}
sum += p;
}
if(!nearby(boosted_bosons[boosted_idx], sum, boosted_bosons[boosted_idx].E())){
throw std::underflow_error("Boson and decays momenta do not match after reshuffling");
}
decays_.emplace(new_idx, decayparticles);
}
}
}
namespace {
template<class ConstIterator, class Iterator>
void label_extremal_qqbar(
ConstIterator born_begin, ConstIterator born_end,
Iterator first_out
){
// find born quarks
const auto firstquark = std::find_if(
born_begin, born_end-1,
[](Particle const & s){ return (is_anyquark(s)); }
);
assert(firstquark != born_end-1);
const auto secondquark = std::find_if(
firstquark+1, born_end,
[](Particle const & s){ return (is_anyquark(s)); }
);
assert(secondquark != born_end);
assert( ( is_quark(*firstquark) && is_antiquark(*secondquark) )
|| ( is_antiquark(*firstquark) && is_quark(*secondquark) ));
assert(first_out->type == ParticleID::gluon);
assert((first_out+1)->type == ParticleID::gluon);
// copy type from born
first_out->type = firstquark->type;
(first_out+1)->type = secondquark->type;
}
} // namespace
void PhaseSpacePoint::label_qqbar(Event const & event){
assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
assert(filter_partons(outgoing_).size() == outgoing_.size());
if(qqbarb_){
label_extremal_qqbar(event.outgoing().cbegin(), event.outgoing().cend(),
outgoing_.begin() );
return;
}
if(qqbarf_){ // same as qqbarb with reversed order
label_extremal_qqbar( event.outgoing().crbegin(), event.outgoing().crend(),
outgoing_.rbegin() );
return;
}
// central qqbar
const auto firstquark = get_central_qqbar(event).first;
// find jets at FO corresponding to the quarks
// technically this isn't necessary for LO
const auto firstjet_idx = get_back_quark_jet(event, firstquark);
// find corresponding jets after resummation
fastjet::ClusterSequence cs{to_PseudoJet(outgoing_), param_.jet_param.def};
auto const jets = fastjet::sorted_by_rapidity(
cs.inclusive_jets( param_.jet_param.min_pt ));
std::vector<int> const resum_indices{ cs.particle_jet_indices({jets}) };
// assert that jets didn't move
assert(nearby_ep( ( event.jets().cbegin()+firstjet_idx )->rapidity(),
jets[ firstjet_idx ].rapidity(), 1e-2) );
assert(nearby_ep( ( event.jets().cbegin()+firstjet_idx+1 )->rapidity(),
jets[ firstjet_idx+1 ].rapidity(), 1e-2) );
// find last partons in first (central) jet
size_t idx_out = 0;
for(size_t i=resum_indices.size()-2; i>0; --i)
if(resum_indices[i] == firstjet_idx){
idx_out = i;
break;
}
assert(idx_out != 0);
// check that there is sufficient pt in jets from the quarks
const double minpartonjetpt = 1. - param_.soft_pt_regulator;
if (outgoing_[idx_out].p.pt()<minpartonjetpt*( event.jets().cbegin()+firstjet_idx )->pt()){
weight_=0.;
status_ = StatusCode::wrong_jets;
return;
}
if (outgoing_[idx_out+1].p.pt()<minpartonjetpt*( event.jets().cbegin()+firstjet_idx+1 )->pt()){
weight_=0.;
status_ = StatusCode::wrong_jets;
return;
}
// check that no additional emission between jets
// such configurations are possible if we have an gluon gets generated
// inside the rapidities of the qqbar chain, but clusted to a
// differnet/outside jet. Changing this is non trivial
if(resum_indices[idx_out+1] != resum_indices[idx_out]+1){
weight_=0.;
status_ = StatusCode::gluon_in_qqbar;
return;
}
outgoing_[idx_out].type = firstquark->type;
outgoing_[idx_out+1].type = std::next(firstquark)->type;
}
void PhaseSpacePoint::label_quarks(Event const & ev){
const auto WZEmit = std::find_if(
begin(ev.outgoing()), end(ev.outgoing()),
[](Particle const & s){ return (std::abs(s.type) == pid::Wp || s.type == pid::Z_photon_mix); }
);
if (WZEmit != end(ev.outgoing())){
if(!qqbarb_) {
const size_t backward_FKL_idx = unob_?1:0;
const auto backward_FKL = std::next(ev.begin_partons(), backward_FKL_idx);
outgoing_[backward_FKL_idx].type = backward_FKL->type;
}
if(!qqbarf_) {
const size_t forward_FKL_idx = unof_?1:0;
const auto forward_FKL = std::prev(ev.end_partons(), 1+forward_FKL_idx);
outgoing_.rbegin()[unof_].type = forward_FKL->type; // NOLINT
}
} else {
if(!is_backward_g_to_h(ev)) {
most_backward_FKL(outgoing_).type = ev.incoming().front().type;
}
if(!is_forward_g_to_h(ev)) {
most_forward_FKL(outgoing_).type = ev.incoming().back().type;
}
}
if(qqbar_mid_||qqbarb_||qqbarf_){
label_qqbar(ev);
}
}
PhaseSpacePoint::PhaseSpacePoint(
Event const & ev, PhaseSpacePointConfig conf, RNG & ran
):
unob_{ev.type() == event_type::unob},
unof_{ev.type() == event_type::unof},
qqbarb_{ev.type() == event_type::qqbar_exb},
qqbarf_{ev.type() == event_type::qqbar_exf},
qqbar_mid_{ev.type() == event_type::qqbar_mid},
param_{std::move(conf)},
status_{unspecified}
{
// legacy code: override new variable with old
if(param_.max_ext_soft_pt_fraction){
param_.soft_pt_regulator = *param_.max_ext_soft_pt_fraction;
param_.max_ext_soft_pt_fraction = {};
}
weight_ = 1;
auto const & Born_jets = ev.jets();
const int ng = sample_ng(ev, ran);
weight_ /= std::tgamma(ng + 1);
const int ng_jets = sample_ng_jets(ev, ng, ran);
std::vector<fastjet::PseudoJet> out_partons = gen_non_jet(
ng - ng_jets, CMINPT, param_.jet_param.min_pt, ran
);
const auto qperp = std::accumulate(
begin(out_partons), end(out_partons),
fastjet::PseudoJet{}
);
std::vector<fastjet::PseudoJet> jets;
std::vector<fastjet::PseudoJet> bosons;
std::tie(jets, bosons) = reshuffle(ev, qperp);
if(weight_ == 0.) {
status_ = failed_reshuffle;
return;
}
if(! pass_resummation_cuts(jets)){
status_ = failed_resummation_cuts;
weight_ = 0.;
return;
}
// split jets in multiple partons
std::vector<fastjet::PseudoJet> jet_partons = split(
ev, jets, ng_jets, ran
);
if(weight_ == 0.) {
status_ = StatusCode::failed_split;
return;
}
const double ymin = is_backward_g_to_h(ev)?
ev.outgoing().front().rapidity():
most_backward_FKL(jet_partons).rapidity()
;
const double ymax = is_forward_g_to_h(ev)?
ev.outgoing().back().rapidity():
most_forward_FKL(jet_partons).rapidity()
;
if(qqbar_mid_){
const int qqbar_backjet = getBackQuarkJet(ev);
rescale_qqbar_rapidities(
out_partons, jets,
ymin, ymax,
qqbar_backjet
);
}
else{
rescale_rapidities(out_partons, ymin, ymax);
}
if(! cluster_jets(out_partons).empty()){
weight_ = 0.;
status_ = StatusCode::empty_jets;
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(ev, out_partons)){
weight_ = 0.;
status_ = StatusCode::wrong_jets;
return;
}
weight_ *= phase_space_normalisation(Born_jets.size(), out_partons.size());
outgoing_.reserve(out_partons.size() + 2); // two slots for possible A, W, Z, H
for( auto it = std::make_move_iterator(out_partons.begin());
it != std::make_move_iterator(out_partons.end());
++it
){
outgoing_.emplace_back( Particle{pid::gluon, *it, {}});
}
assert(!outgoing_.empty());
label_quarks(ev);
if(weight_ == 0.) {
//! @TODO optimise s.t. this is not possible
// status is handled internally
return;
}
// reattach bosons & decays
if(!bosons.empty()){
try {
boost_AWZH_bosons_from(bosons, ev);
} catch (std::underflow_error const & e){
weight_ = 0.;
status_ = StatusCode::failed_reshuffle;
return;
}
}
reconstruct_incoming(ev.incoming());
status_ = StatusCode::good;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_non_jet(
int const ng_non_jet, double const ptmin, double const ptmax, RNG & ran
){
// heuristic parameters for pt sampling
const double ptpar = 1.3 + ng_non_jet/5.;
const double temp1 = std::atan((ptmax - ptmin)/ptpar);
std::vector<fastjet::PseudoJet> partons(ng_non_jet);
for(int i = 0; i < ng_non_jet; ++i){
const double r1 = ran.flat();
const double pt = ptmin + ptpar*std::tan(r1*temp1);
const double temp2 = std::cos(r1*temp1);
const double phi = 2*M_PI*ran.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.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 sorted_by_rapidity(partons);
}
void PhaseSpacePoint::rescale_qqbar_rapidities(
std::vector<fastjet::PseudoJet> & out_partons,
std::vector<fastjet::PseudoJet> const & jets,
const double ymin1, const double ymax2,
const int qqbar_backjet
){
const double ymax1 = jets[qqbar_backjet].rapidity();
const double ymin2 = jets[qqbar_backjet+1].rapidity();
constexpr double ep = 1e-7;
const double tot_y = ymax1 - ymin1 + ymax2 - ymin2;
std::vector<std::reference_wrapper<fastjet::PseudoJet>> refpart(
out_partons.begin(), out_partons.end());
double ratio = (ymax1 - ymin1)/tot_y;
const auto gap{ std::find_if(refpart.begin(), refpart.end(),
[ratio](fastjet::PseudoJet const & p){
return (p.rapidity()>=ratio);} ) };
double ymin = ymin1;
double ymax = ymax1;
double dy = ymax - ymin - 2*ep;
double offset = 0.;
for(auto it_part=refpart.begin(); it_part<refpart.end(); ++it_part){
if(it_part == gap){
ymin = ymin2;
ymax = ymax2;
dy = ymax - ymin - 2*ep;
offset = ratio;
ratio = 1-ratio;
}
fastjet::PseudoJet & part = *it_part;
assert(offset <= part.rapidity() && part.rapidity() < ratio+offset);
const double y = ymin + ep + dy*((part.rapidity()-offset)/ratio);
part.reset_momentum_PtYPhiM(part.pt(), y, part.phi());
weight_ *= tot_y-4.*ep;
assert(ymin <= part.rapidity() && part.rapidity() <= ymax);
}
assert(is_sorted(begin(out_partons), end(out_partons), rapidity_less{}));
}
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(Event const & ev) const{
const double dy = estimate_emission_rapidity_range(ev);
const double R = param_.jet_param.def.R();
// jets into which we predominantly emit
const int njets = ev.jets().size() - unof_ - unob_ - qqbarb_ - qqbarf_; //NOLINT
assert(njets >= 1);
const size_t nextremal_jets = std::min(njets, 2);
const double p_J_y_large = (njets - nextremal_jets/2.)*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(Event const & event, int ng, RNG & ran){
const double p_J = probability_in_jet(event);
std::binomial_distribution<> bin_dist(ng, p_J);
const int ng_J = bin_dist(ran);
weight_ *= std::pow(p_J, -ng_J)*std::pow(1 - p_J, ng_J - ng);
return ng_J;
}
std::pair< std::vector<fastjet::PseudoJet>,
std::vector<fastjet::PseudoJet> >
PhaseSpacePoint::reshuffle(
Event const & ev,
fastjet::PseudoJet const & q
){
// Create a copy of the outgoing momenta not containing decay products
std::vector<fastjet::PseudoJet const *> born_momenta;
born_momenta.reserve(ev.jets().size());
std::transform(ev.jets().cbegin(), ev.jets().cend(),
back_inserter(born_momenta),
[](fastjet::PseudoJet const & t) { return &t; });
auto bosons = filter_AWZH_bosons(ev.outgoing());
std::vector<fastjet::PseudoJet const *> p_boson_momenta;
std::transform(bosons.cbegin(), bosons.cend(),
back_inserter(p_boson_momenta),
[](Particle const & t) { return &(t.p); });
std::vector<fastjet::PseudoJet> boson_momenta;
std::transform(bosons.cbegin(), bosons.cend(),
back_inserter(boson_momenta),
[](Particle const & t) { return t.p; });
// reshuffle all momenta
if(q == fastjet::PseudoJet{0, 0, 0, 0}) return {ev.jets(), boson_momenta};
// add bosons to reshuffling
if(!bosons.empty()) {
born_momenta.insert( born_momenta.end(), p_boson_momenta.begin(), p_boson_momenta.end() );
}
auto shuffle_momenta = resummation_jet_momenta(born_momenta, q);
if(shuffle_momenta.empty()){
weight_ = 0;
return {};
}
// additional Jacobian to ensure Born integration over delta gives 1
weight_ *= resummation_jet_weight(born_momenta, q);
// take out bosons again
if(!bosons.empty()) {
std::vector<fastjet::PseudoJet> shuffle_bosons;
for(size_t i = 0; i < bosons.size(); ++i) {
shuffle_bosons.push_back(shuffle_momenta.back());
shuffle_momenta.pop_back();
}
std::reverse(shuffle_bosons.begin(), shuffle_bosons.end());
return {shuffle_momenta, shuffle_bosons};
}
return {shuffle_momenta, {}};
}
std::vector<int> PhaseSpacePoint::distribute_jet_partons(
int ng_jets, std::vector<fastjet::PseudoJet> const & jets, RNG & ran
){
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_||qqbarb_) && jets[0].delta_R(jets[1]) > R_eff){
++first_valid_jet;
--num_valid_jets;
}
else if((unof_||qqbarf_) && 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.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() == UID::backward_fkl;
}
) != 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() == UID::forward_fkl;
}
) != jet_partons.rend();
}
} // namespace
#endif
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
Event const & Born_event,
std::vector<fastjet::PseudoJet> const & jets,
int ng_jets
, RNG & ran
){
return split(
Born_event,
jets,
distribute_jet_partons(ng_jets, jets, ran),
ran
);
}
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_.soft_pt_regulator;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
Event const & Born_event,
std::vector<fastjet::PseudoJet> const & jets,
std::vector<int> const & np,
RNG & ran
){
assert(! jets.empty());
assert(jets.size() == np.size());
assert(pass_resummation_cuts(jets));
constexpr auto no_such_jet_idx = std::numeric_limits<std::size_t>::max();
const size_t most_backward_FKL_idx = is_backward_g_to_h(Born_event)?
no_such_jet_idx: // we have backward Higgs instead of FKL jet
(0 + unob_ + qqbarb_); // NOLINT
const size_t most_forward_FKL_idx = is_forward_g_to_h(Born_event)?
no_such_jet_idx: // we have forward Higgs instead of FKL jet
(jets.size() - 1 - unof_ - qqbarf_); // NOLINT
const size_t qqbar_jet_idx = qqbar_mid_?
getBackQuarkJet(Born_event):
no_such_jet_idx;
auto const & jet = param_.jet_param;
const JetSplitter jet_splitter{jet.def, jet.min_pt};
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], ran);
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
// also mark qqbar_mid partons, and apply appropriate pt cut.
auto extremal = end(jet_partons);
if (i == most_backward_FKL_idx){ //FKL backward emission
extremal = std::min_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(UID::backward_fkl);
}
else if(((unob_ || qqbarb_) && i == 0)){
// unordered/qqbarb
extremal = std::min_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index((unob_)?UID::unob:UID::qqbarb);
}
else if (i == most_forward_FKL_idx){
extremal = std::max_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(UID::forward_fkl);
}
else if(((unof_ || qqbarf_) && i == jets.size() - 1)){
// unordered/qqbarf
extremal = std::max_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index((unof_)?UID::unof:UID::qqbarf);
}
else if((qqbar_mid_ && i == qqbar_jet_idx)){
extremal = std::max_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(UID::qqbar_mid1);
}
else if((qqbar_mid_ && i == qqbar_jet_idx+1)){
extremal = std::min_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(UID::qqbar_mid2);
}
if(
extremal != end(jet_partons)
&& !pass_extremal_cuts(*extremal, jets[i])
){
weight_ = 0;
return {};
}
}
assert(is_backward_g_to_h(Born_event) || tagged_FKL_backward(jet_partons));
assert(is_forward_g_to_h(Born_event) || tagged_FKL_forward(jet_partons));
std::sort(begin(jet_partons), end(jet_partons), rapidity_less{});
if(
!extremal_ok(Born_event, jet_partons)
|| !split_preserved_jets(jets, jet_partons)
){
weight_ = 0.;
return {};
}
return jet_partons;
}
bool PhaseSpacePoint::extremal_ok(
Event const & Born_event,
std::vector<fastjet::PseudoJet> const & partons
) const{
assert(std::is_sorted(begin(partons), end(partons), rapidity_less{}));
if(unob_ && partons.front().user_index() != UID::unob) return false;
if(unof_ && partons.back().user_index() != UID::unof) return false;
if(qqbarb_ && partons.front().user_index() != UID::qqbarb) return false;
if(qqbarf_ && partons.back().user_index() != UID::qqbarf) return false;
if(is_backward_g_to_h(Born_event)) {
if(partons.front().rapidity() < Born_event.outgoing().front().rapidity()){
return false;
}
} else if(most_backward_FKL(partons).user_index() != UID::backward_fkl) {
return false;
}
if(is_forward_g_to_h(Born_event)) {
return partons.back().rapidity() <= Born_event.outgoing().back().rapidity();
}
return most_forward_FKL(partons).user_index() == UID::forward_fkl;
}
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 = 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_ + qqbarb_];
}
template<class Particle>
Particle const & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> const & partons
) const{
const size_t idx = partons.size() - 1 - unof_ - qqbarf_;
assert(idx < partons.size());
return partons[idx];
}
template<class Particle>
Particle & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> & partons
) const{
return partons[0 + unob_ + qqbarb_];
}
template<class Particle>
Particle & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> & partons
) const{
const size_t idx = partons.size() - 1 - unof_ - qqbarf_;
assert(idx < partons.size());
return partons[idx];
}
bool PhaseSpacePoint::contains_idx(
fastjet::PseudoJet const & jet, fastjet::PseudoJet const & parton
) const {
auto const & constituents = jet.constituents();
const int idx = parton.user_index();
const bool injet = std::find_if(
begin(constituents), end(constituents),
[idx](fastjet::PseudoJet const & con){return con.user_index() == idx;}
) != end(constituents);
const double minpartonjetpt = 1. - param_.soft_pt_regulator;
return ((parton.pt()>minpartonjetpt*jet.pt())&&injet);
}
bool PhaseSpacePoint::jets_ok(
Event const & Born_event,
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_event.jets().size()) return false;
int in_jet = 0;
for(auto const & jet : jets){
assert(jet.has_constituents());
for(auto && parton: jet.constituents()){
if(is_nonjet_parton(parton)) return false;
}
in_jet += jet.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(
!is_backward_g_to_h(Born_event) &&
!contains_idx(most_backward_FKL(jets), most_backward_FKL(partons))
) return false;
if(
!is_forward_g_to_h(Born_event)
&& !contains_idx(most_forward_FKL(jets), most_forward_FKL(partons))
) return false;
if(unob_ && !contains_idx(jets.front(), partons.front())) return false;
if(qqbarb_ && !contains_idx(jets.front(), partons.front())) return false;
if(unof_ && !contains_idx(jets.back(), partons.back())) return false;
if(qqbarf_ && !contains_idx(jets.back(), partons.back())) return false;
#ifndef NDEBUG
for(size_t i = 0; i < jets.size(); ++i){
assert(nearby_ep(jets[i].rapidity(), Born_event.jets()[i].rapidity(), 1e-2));
}
#endif
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());
}
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