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diff --git a/src/Event.cc b/src/Event.cc
index 1e4a3cf..7dcd400 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -1,1403 +1,1405 @@
/**
* \authors The HEJ collaboration (see AUTHORS for details)
* \date 2019-2020
* \copyright GPLv2 or later
*/
#include "HEJ/Event.hh"
#include <algorithm>
#include <cassert>
#include <cstdlib>
#include <iomanip>
#include <iterator>
#include <memory>
#include <numeric>
#include <optional>
#include <ostream>
#include <string>
#include <utility>
#include "fastjet/ClusterSequence.hh"
#include "fastjet/JetDefinition.hh"
#include "fastjet/PseudoJet.hh"
#include "LHEF/LHEF.h"
#include "HEJ/Constants.hh"
#include "HEJ/EWConstants.hh"
#include "HEJ/PDG_codes.hh"
#include "HEJ/RNG.hh"
#include "HEJ/exceptions.hh"
#include "HEJ/LorentzVector.hh"
#include "HEJ/utility.hh"
namespace HEJ {
/**
* returns all EventTypes implemented in HEJ
*/
size_t implemented_types(std::vector<Particle> const & bosons){
using namespace event_type;
// no bosons
if(bosons.empty()) return FKL | unob | unof | qqbar_exb | qqbar_exf | qqbar_mid;
// 1 boson
if(bosons.size()== 1) {
switch (bosons[0].type) {
case ParticleID::Wp:
case ParticleID::Wm:
return FKL | unob | unof | qqbar_exb | qqbar_exf | qqbar_mid;
case ParticleID::Z_photon_mix:
return FKL | unob | unof;
case ParticleID::h:
return FKL | unob | unof;
default:
return non_resummable;
}
}
// 2 bosons
if(bosons.size() == 2) {
// Resum only samesign W events
if(bosons[0].type == ParticleID::Wp && bosons[1].type == ParticleID::Wp) {
return FKL;
}
else if(bosons[0].type == ParticleID::Wm && bosons[1].type == ParticleID::Wm) {
return FKL;
}
}
return non_resummable;
}
namespace {
using std::size_t;
//! LHE status codes
namespace lhe_status {
enum Status: int {
in = -1,
decay = 2,
out = 1,
};
}
using LHE_Status = lhe_status::Status;
//! true if leptonic W decay
bool valid_W_decay( int const w_type, // sign of W
std::vector<Particle> const & decays
){
if(decays.size() != 2) // no 1->2 decay
return false;
const int pidsum = decays[0].type + decays[1].type;
if( std::abs(pidsum) != 1 || pidsum != w_type ) // correct charge
return false;
// leptonic decay (only check first, second follows from pidsum)
if( w_type == 1 ) // W+
return is_antilepton(decays[0]) || is_neutrino(decays[0]);
// W-
return is_lepton(decays[0]) || is_antineutrino(decays[0]);
}
//! true for Z decay to charged leptons
bool valid_Z_decay(std::vector<Particle> const & decays){
if(decays.size() != 2) // no 1->2 decay
return false;
const int pidsum = decays[0].type + decays[1].type;
if( std::abs(pidsum) != 0 ) // correct charge
return false;
// leptonic decay (only check first, second follows from pidsum)
return is_anylepton(decays[0]) && !is_anyneutrino(decays[0]);
}
//! true if supported decay
bool valid_decay(std::vector<Particle> const & decays){
return valid_W_decay(+1, decays) || // Wp
valid_W_decay(-1, decays) || // Wm
valid_Z_decay( decays) // Z/gamma
;
}
/// @name helper functions to determine event type
//@{
/**
* \brief check if final state valid for HEJ
*
* check final state has the expected number of valid decays for bosons
* and all the rest are quarks or gluons
*/
bool final_state_ok(Event const & ev){
size_t invalid_decays = ev.decays().size();
std::vector<Particle> const & outgoing = ev.outgoing();
for( size_t i=0; i<outgoing.size(); ++i ){
auto const & out{ outgoing[i] };
if(is_AWZH_boson(out.type)){
auto const decay = ev.decays().find(i);
// Momentum Conservating Decays
if(decay != ev.decays().cend()) {
auto const progeny = decay -> second;
fastjet::PseudoJet res = std::accumulate(
progeny.cbegin(), progeny.cend(), fastjet::PseudoJet(),
[](fastjet::PseudoJet & sum, Particle const & p) -> fastjet::PseudoJet {
return std::move(sum) + p.p;
}
);
if(!nearby(out.p, res, out.E())){ return false; }
}
// W decays (required)
if(std::abs(out.type) == ParticleID::Wp){
if( decay != ev.decays().cend() &&
valid_W_decay(out.type>0?+1:-1, decay->second)
){
--invalid_decays;
}
else return false;
}
// Higgs decays (optional)
else if(out.type == ParticleID::h){
if(decay != ev.decays().cend()) --invalid_decays;
}
// Z decays (required)
else if(out.type == ParticleID::Z_photon_mix){
if( decay != ev.decays().cend() &&
valid_Z_decay(decay->second)
){
--invalid_decays;
}
else return false;
}
}
else if(! is_parton(out.type)) return false;
}
// any invalid decays?
return invalid_decays == 0;
}
/**
* \brief function which determines if type change is consistent with Wp emission.
* @param in incoming Particle id
* @param out outgoing Particle id
* @param is_qqbar Current both incoming/both outgoing?
*
* \see is_Wm_Change
*/
bool is_Wp_Change(ParticleID in, ParticleID out, bool is_qqbar){
using namespace pid;
if(!is_qqbar && (in==d_bar || in==u || in==s_bar || in==c))
return out == (in-1);
if( is_qqbar && (in==d || in==u_bar || in==s || in==c_bar))
return out == -(in+1);
return false;
}
/**
* \brief function which determines if type change is consistent with Wm emission.
* @param in incoming Particle id
* @param out outgoing Particle id
* @param is_qqbar Current both incoming/both outgoing?
*
* Ensures that change type of quark line is possible by a flavour changing
* Wm emission. Allows checking of is_qqbar currents also.
*/
bool is_Wm_Change(ParticleID in, ParticleID out, bool is_qqbar){
using namespace pid;
if(!is_qqbar && (in==d || in==u_bar || in==s || in==c_bar))
return out == (in+1);
if( is_qqbar && (in==d_bar || in==u || in==s_bar || in==c))
return out == -(in-1);
return false;
}
/**
* \brief checks if particle type remains same from incoming to outgoing
* @param in incoming Particle
* @param out outgoing Particle
* @param is_qqbar Current both incoming/outgoing?
*/
bool no_flavour_change(ParticleID in, ParticleID out, bool is_qqbar){
const int qqbarCurrent = is_qqbar?-1:1;
if(std::abs(in)<=pid::top || in==pid::gluon)
return (in==out*qqbarCurrent);
return false;
}
bool has_enough_jets(Event const & event){
if(event.jets().size() >= 2) return true;
if(event.jets().empty()) return false;
// check for h+jet
const auto the_higgs = std::find_if(
begin(event.outgoing()), end(event.outgoing()),
[](const auto & particle) { return particle.type == pid::higgs; }
);
return the_higgs != end(event.outgoing());
}
bool is_gluon_to_Higgs(const ParticleID in, const ParticleID out) {
return in == pid::gluon && out == pid::Higgs;
}
/**
* \brief check if we have a valid Impact factor
* @param in incoming Particle
* @param out outgoing Particle
* @param is_qqbar Current both incoming/outgoing?
* @param W_change returns +1 if Wp, -1 if Wm, else 0
*/
bool is_valid_impact_factor(
ParticleID in, ParticleID out, bool is_qqbar, int & W_change
){
if( no_flavour_change(in, out, is_qqbar) || is_gluon_to_Higgs(in, out)) {
return true;
}
if( is_Wp_Change(in, out, is_qqbar) ) {
W_change+=1;
return true;
}
if( is_Wm_Change(in, out, is_qqbar) ) {
W_change-=1;
return true;
}
return false;
}
bool is_extremal_higgs_off_quark(
const ParticleID in,
const ParticleID extremal_out,
const ParticleID out
) {
return in == out && extremal_out == pid::higgs && is_anyquark(in);
}
//! Returns all possible classifications from the impact factors
// the beginning points are changed s.t. after the the classification they
// point to the beginning of the (potential) FKL chain
// sets W_change: + if Wp change
// 0 if no change
// - if Wm change
// This function can be used with forward & backwards iterators
template<class OutIterator>
size_t possible_impact_factors(
ParticleID incoming_id, // incoming
OutIterator & begin_out, OutIterator const & end_out, // outgoing
int & W_change, std::vector<Particle> const & boson,
bool const backward // backward?
){
using namespace event_type;
if(begin_out == end_out) return non_resummable;
// keep track of all states that we don't test
size_t not_tested = qqbar_mid;
if(backward)
not_tested |= unof | qqbar_exf;
else
not_tested |= unob | qqbar_exb;
// Is this LL current?
if( is_valid_impact_factor(incoming_id, begin_out->type, false, W_change) ){
++begin_out;
return not_tested | FKL;
}
// q -> H q and qbar -> H qbar are technically not LL,
// but we treat them as such anyway
const auto next = std::next(begin_out);
if(
// first ensure that the next particle is not part of the *other* impact factor
next != end_out
&& is_extremal_higgs_off_quark(incoming_id, begin_out->type, next->type)
) {
std::advance(begin_out, 2);
return not_tested | FKL;
}
// or NLL current?
// -> needs two partons in two different jets
if( std::distance(begin_out, end_out)>=2
){
auto next = std::next(begin_out);
// Is this unordered emisson?
if( incoming_id!=pid::gluon && begin_out->type==pid::gluon ){
if( is_valid_impact_factor(
incoming_id, next->type, false, W_change )
){
// veto Higgs inside uno
assert(next!=end_out);
if( !boson.empty() && boson.front().type == ParticleID::h
){
if( (backward && boson.front().rapidity() < next->rapidity())
||(!backward && boson.front().rapidity() > next->rapidity()))
return non_resummable;
}
begin_out = std::next(next);
return not_tested | (backward?unob:unof);
}
}
// Is this QQbar?
else if( incoming_id==pid::gluon ){
if( is_valid_impact_factor(
begin_out->type, next->type, true, W_change )
){
// veto Higgs inside qqbar
assert(next!=end_out);
if( !boson.empty() && boson.front().type == ParticleID::h
){
if( (backward && boson.front().rapidity() < next->rapidity())
||(!backward && boson.front().rapidity() > next->rapidity()))
return non_resummable;
}
begin_out = std::next(next);
return not_tested | (backward?qqbar_exb:qqbar_exf);
}
}
}
return non_resummable;
}
//! Returns all possible classifications from central emissions
// the beginning points are changed s.t. after the the classification they
// point to the end of the emission chain
// sets W_change: + if Wp change
// 0 if no change
// - if Wm change
template<class OutIterator>
size_t possible_central(
OutIterator & begin_out, OutIterator const & end_out,
int & W_change, std::vector<Particle> const & boson
){
using namespace event_type;
// if we already passed the central chain,
// then it is not a valid all-order state
if(std::distance(begin_out, end_out) < 0) return non_resummable;
// keep track of all states that we don't test
size_t possible = unob | unof
| qqbar_exb | qqbar_exf;
// Find the first quark or antiquark emission
begin_out = std::find_if(
begin_out, end_out,
[](Particle const & p) { return is_anyquark(p); }
);
// end of chain -> FKL
if( begin_out==end_out ){
return possible | FKL;
}
// is this a qqbar-pair?
// needs two partons in two separate jets
auto next = std::next(begin_out);
if(
next != end_out
&& is_valid_impact_factor(begin_out->type, next->type, true, W_change)
){
// veto Higgs inside qqbar
if( !boson.empty() && boson.front().type == ParticleID::h
&& boson.front().rapidity() > begin_out->rapidity()
&& boson.front().rapidity() < next->rapidity()
){
return non_resummable;
}
begin_out = std::next(next);
// remaining chain should be pure FKL (gluon or higgs)
if(std::any_of(
begin_out, end_out,
[](Particle const & p) { return is_anyquark(p); }
)) {
return non_resummable;
}
return possible | qqbar_mid;
}
return non_resummable;
}
namespace {
bool is_parton_or_higgs(Particle const & p) {
return is_parton(p) || p.type == pid::higgs;
}
}
/**
* \brief Checks for all event types
* @param ev Event
* @returns Event Type
*
*/
event_type::EventType classify(Event const & ev){
using namespace event_type;
if(! has_enough_jets(ev))
return not_enough_jets;
// currently we can't handle multiple boson states in the ME. So they are
// considered "bad_final_state" even though the "classify" could work with
// them.
if(! final_state_ok(ev))
return bad_final_state;
// initialise variables
auto const & in = ev.incoming();
// range for current checks
auto begin_out = boost::make_filter_iterator(
is_parton_or_higgs, cbegin(ev.outgoing()), cend(ev.outgoing())
);
auto rbegin_out = std::make_reverse_iterator(
boost::make_filter_iterator(
is_parton_or_higgs, cend(ev.outgoing()), cend(ev.outgoing())
)
);
assert(std::distance(begin(in), end(in)) == 2);
assert(std::distance(begin_out, rbegin_out.base()) >= 2);
assert(std::is_sorted(begin_out, rbegin_out.base(), rapidity_less{}));
auto const bosons{ filter_AWZH_bosons(ev.outgoing()) };
// keep track of potential W couplings, at the end the sum should be 0
int remaining_Wp = 0;
int remaining_Wm = 0;
for(auto const & boson : bosons){
if(boson.type == ParticleID::Wp) ++remaining_Wp;
else if(boson.type == ParticleID::Wm) ++remaining_Wm;
}
size_t final_type = ~(not_enough_jets | bad_final_state);
// check forward impact factor
int W_change = 0;
final_type &= possible_impact_factors(
in.front().type,
begin_out, rbegin_out.base(),
W_change, bosons, true );
if( final_type == non_resummable )
return non_resummable;
if(W_change>0) remaining_Wp-=W_change;
else if(W_change<0) remaining_Wm+=W_change;
// check backward impact factor
W_change = 0;
final_type &= possible_impact_factors(
in.back().type,
rbegin_out, std::make_reverse_iterator(begin_out),
W_change, bosons, false );
if( final_type == non_resummable )
return non_resummable;
if(W_change>0) remaining_Wp-=W_change;
else if(W_change<0) remaining_Wm+=W_change;
// check central emissions
W_change = 0;
final_type &= possible_central(
begin_out, rbegin_out.base(), W_change, bosons );
if( final_type == non_resummable )
return non_resummable;
if(W_change>0) remaining_Wp-=W_change;
else if(W_change<0) remaining_Wm+=W_change;
// Check whether the right number of Ws are present
if( remaining_Wp != 0 || remaining_Wm != 0 ) return non_resummable;
// result has to be unique
if( (final_type & (final_type-1)) != 0) return non_resummable;
// check that each sub processes is implemented
// (has to be done at the end)
if( (final_type & ~implemented_types(bosons)) != 0 )
return non_resummable;
return static_cast<EventType>(final_type);
}
//@}
Particle extract_particle(LHEF::HEPEUP const & hepeup, size_t i){
auto id = static_cast<ParticleID>(hepeup.IDUP[i]);
auto colour = is_parton(id)?hepeup.ICOLUP[i]:std::optional<Colour>();
return { id,
{ hepeup.PUP[i][0], hepeup.PUP[i][1],
hepeup.PUP[i][2], hepeup.PUP[i][3] },
colour
};
}
bool is_decay_product(std::pair<int, int> const & mothers){
if(mothers.first == 0) return false;
return mothers.second == 0 || mothers.first == mothers.second;
}
} // namespace
Event::EventData::EventData(LHEF::HEPEUP const & hepeup){
parameters.central = EventParameters{
hepeup.scales.mur, hepeup.scales.muf, hepeup.XWGTUP
};
size_t in_idx = 0;
for (int i = 0; i < hepeup.NUP; ++i) {
// skip decay products
// we will add them later on, but we have to ensure that
// the decayed particle is added before
if(is_decay_product(hepeup.MOTHUP[i])) continue;
auto particle = extract_particle(hepeup, i);
// needed to identify mother particles for decay products
particle.p.set_user_index(i+1);
if(hepeup.ISTUP[i] == LHE_Status::in){
if(in_idx > incoming.size()) {
throw std::invalid_argument{
"Event has too many incoming particles"
};
}
incoming[in_idx++] = std::move(particle);
}
else outgoing.emplace_back(std::move(particle));
}
// add decay products
for (int i = 0; i < hepeup.NUP; ++i) {
if(!is_decay_product(hepeup.MOTHUP[i])) continue;
const int mother_id = hepeup.MOTHUP[i].first;
const auto mother = std::find_if(
begin(outgoing), end(outgoing),
[mother_id](Particle const & particle){
return particle.p.user_index() == mother_id;
}
);
if(mother == end(outgoing)){
throw std::invalid_argument{"invalid decay product parent"};
}
const int mother_idx = std::distance(begin(outgoing), mother);
assert(mother_idx >= 0);
decays[mother_idx].emplace_back(extract_particle(hepeup, i));
}
}
Event::Event(
UnclusteredEvent const & ev,
fastjet::JetDefinition const & jet_def, double const min_jet_pt
):
Event( Event::EventData{
ev.incoming, ev.outgoing, ev.decays,
Parameters<EventParameters>{ev.central, ev.variations}
}.cluster(jet_def, min_jet_pt) )
{}
//! @TODO remove in HEJ 2.2.0
UnclusteredEvent::UnclusteredEvent(LHEF::HEPEUP const & hepeup){
Event::EventData const evData{hepeup};
incoming = evData.incoming;
outgoing = evData.outgoing;
decays = evData.decays;
central = evData.parameters.central;
variations = evData.parameters.variations;
}
void Event::EventData::sort(){
// sort particles
std::sort(
begin(incoming), end(incoming),
[](Particle const & o1, Particle const & o2){return o1.p.pz()<o2.p.pz();}
);
auto old_outgoing = std::move(outgoing);
std::vector<size_t> idx(old_outgoing.size());
std::iota(idx.begin(), idx.end(), 0);
std::sort(idx.begin(), idx.end(), [&old_outgoing](size_t i, size_t j){
return old_outgoing[i].rapidity() < old_outgoing[j].rapidity();
});
outgoing.clear();
outgoing.reserve(old_outgoing.size());
for(size_t i: idx) {
outgoing.emplace_back(std::move(old_outgoing[i]));
}
// find decays again
if(!decays.empty()){
auto old_decays = std::move(decays);
decays.clear();
for(size_t i=0; i<idx.size(); ++i) {
auto decay = old_decays.find(idx[i]);
if(decay != old_decays.end())
decays.emplace(i, std::move(decay->second));
}
assert(old_decays.size() == decays.size());
}
}
namespace {
// use valid_X_decay to determine boson type
ParticleID reconstruct_type(std::vector<Particle> const & progeny) {
if(valid_W_decay(+1, progeny)) { return ParticleID::Wp; }
if(valid_W_decay(-1, progeny)) { return ParticleID::Wm; }
if(valid_Z_decay(progeny)) { return ParticleID::Z_photon_mix; }
throw not_implemented{
"final state with decay X -> "
+ name(progeny[0].type)
+ " + "
+ name(progeny[1].type)
};
}
// reconstruct particle with explicit ParticleID
Particle reconstruct_boson(
std::vector<Particle> const & progeny,
ParticleID const & type
) {
Particle progenitor;
progenitor.p = progeny[0].p + progeny[1].p;
progenitor.type = type;
return progenitor;
}
// reconstruct via call to reconstruct_type
Particle reconstruct_boson(std::vector<Particle> const & progeny) {
Particle progenitor {reconstruct_boson(progeny, reconstruct_type(progeny))};
assert(is_AWZH_boson(progenitor));
return progenitor;
}
using GroupedParticles = std::vector<std::vector<Particle> >;
using Decay = std::pair<Particle, std::vector<Particle> >;
using Decays = std::vector<Decay>;
// return groups of reconstructable progeny
std::vector<GroupedParticles> group_progeny(std::vector<Particle> & leptons) {
/**
Warning: The partition in to charged/neutral leptons is valid ONLY for WW.
**/
assert(leptons.size() == 4);
auto const begin_neutrino = std::partition(
begin(leptons), end(leptons),
[](Particle const & p) {return !is_anyneutrino(p);}
);
std::vector<Particle> neutrinos (begin_neutrino, end(leptons));
leptons.erase(begin_neutrino, end(leptons));
if(leptons.size() != 2 || neutrinos.size() != 2) { return {}; }
assert(leptons.size() == 2 && neutrinos.size() == 2);
std::vector<GroupedParticles> valid_groupings;
GroupedParticles candidate_grouping{{leptons[0], neutrinos[0]}, {leptons[1], neutrinos[1]}};
if(valid_decay(candidate_grouping.front()) && valid_decay(candidate_grouping.back())) {
valid_groupings.emplace_back(std::move(candidate_grouping));
}
candidate_grouping = {{leptons[1], neutrinos[0]}, {leptons[0], neutrinos[1]}};
if(valid_decay(candidate_grouping.front()) && valid_decay(candidate_grouping.back())) {
valid_groupings.emplace_back(std::move(candidate_grouping));
}
return valid_groupings;
}
// 'best' decay ordering measure
double decay_measure(const Particle& reconstructed, EWConstants const & params) {
ParticleProperties ref = params.prop(reconstructed.type);
return std::abs(reconstructed.p.m() - ref.mass);
}
// decay_measure accumulated over decays
double decay_measure(Decays const & decays, EWConstants const & params) {
return
std::accumulate(
cbegin(decays), cend(decays), 0.,
[&params] (double dm, Decay const & decay) -> double {
return dm + decay_measure(decay.first, params);
}
);
}
// select best combination of decays for the event
Decays select_decays
(
std::vector<Particle> & leptons,
EWConstants const & ew_parameters
) {
std::vector<GroupedParticles> groupings = group_progeny(leptons);
std::vector<Decays> valid_decays;
valid_decays.reserve(groupings.size());
// Reconstruct all groupings
for(GroupedParticles const & group : groupings) {
Decays decays;
for(auto const & progeny : group) {
decays.emplace_back(make_pair(reconstruct_boson(progeny), progeny));
}
valid_decays.emplace_back(decays);
}
if (valid_decays.empty()) {
throw not_implemented{"No supported intermediate reconstruction available"};
}
if (valid_decays.size() == 1) {
return valid_decays[0];
}
// select decay with smallest decay_measure
auto selected = std::min_element(cbegin(valid_decays), cend(valid_decays),
[&ew_parameters] (auto const & d1, auto const & d2) -> bool {
return decay_measure(d1, ew_parameters) < decay_measure(d2, ew_parameters);
}
);
return *selected;
}
} // namespace
void Event::EventData::reconstruct_intermediate(EWConstants const & ew_parameters) {
auto const begin_leptons = std::partition(
begin(outgoing), end(outgoing),
[](Particle const & p) {return !is_anylepton(p);}
);
std::vector<Particle> leptons(begin_leptons, end(outgoing));
outgoing.erase(begin_leptons, end(outgoing));
if(leptons.empty()) { return; } // nothing to do
if(leptons.size() == 2) {
outgoing.emplace_back(reconstruct_boson(leptons));
std::sort(begin(leptons), end(leptons), type_less{});
decays.emplace(outgoing.size()-1, std::move(leptons));
}
else if(leptons.size() == 4) {
Decays valid_decays = select_decays(leptons, ew_parameters);
for(auto &decay : valid_decays) {
outgoing.emplace_back(decay.first);
std::sort(begin(decay.second), end(decay.second), type_less{});
decays.emplace(outgoing.size()-1, std::move(decay.second));
}
}
else {
throw not_implemented {
std::to_string(leptons.size())
+ " leptons in the final state"
};
}
}
namespace {
void repair_momentum(fastjet::PseudoJet & p, const double tolerance) {
if(p.e() > 0. && p.m2() != 0. && (p.m2() < tolerance * tolerance)) {
const double rescale = std::sqrt(p.modp() / p.e());
const double e = p.e() * rescale;
const double px = p.px() / rescale;
const double py = p.py() / rescale;
const double pz = p.pz() / rescale;
p.reset(px, py, pz, e);
}
}
}
void Event::EventData::repair_momenta(const double tolerance) {
for(auto & in: incoming) {
if(is_massless(in)) {
const double px = (std::abs(in.px()) < tolerance)?0.:in.px();
const double py = (std::abs(in.py()) < tolerance)?0.:in.py();
in.p.reset(px, py, in.p.pz(), in.p.e());
repair_momentum(in.p, tolerance);
}
}
for(auto & out: outgoing) {
if(is_massless(out)) repair_momentum(out.p, tolerance);
}
for(auto & decay: decays) {
for(auto & out: decay.second) {
if(is_massless(out)) repair_momentum(out.p, tolerance);
}
}
}
Event Event::EventData::cluster(
fastjet::JetDefinition const & jet_def, double const min_jet_pt
){
sort();
return Event{ std::move(incoming), std::move(outgoing), std::move(decays),
std::move(parameters),
jet_def, min_jet_pt
};
}
Event::Event(
std::array<Particle, 2> && incoming,
std::vector<Particle> && outgoing,
std::unordered_map<size_t, std::vector<Particle>> && decays,
Parameters<EventParameters> && parameters,
fastjet::JetDefinition const & jet_def,
double const min_jet_pt
): incoming_{std::move(incoming)},
outgoing_{std::move(outgoing)},
decays_{std::move(decays)},
parameters_{std::move(parameters)},
cs_{ to_PseudoJet( filter_partons(outgoing_) ), jet_def },
min_jet_pt_{min_jet_pt}
{
jets_ = sorted_by_rapidity(cs_.inclusive_jets(min_jet_pt_));
assert(std::is_sorted(begin(outgoing_), end(outgoing_),
rapidity_less{}));
type_ = classify(*this);
}
namespace {
//! check that Particles have a reasonable colour
bool correct_colour(Particle const & part){
ParticleID id{ part.type };
if(!is_parton(id))
return !part.colour;
if(!part.colour)
return false;
Colour const & col{ *part.colour };
if(is_quark(id))
return col.first != 0 && col.second == 0;
if(is_antiquark(id))
return col.first == 0 && col.second != 0;
assert(id==ParticleID::gluon);
return col.first != 0 && col.second != 0 && col.first != col.second;
}
//! Connect parton to t-channel colour line & update the line
//! returns false if connection not possible
template<class OutIterator>
bool try_connect_t(OutIterator const & it_part, Colour & line_colour){
if( line_colour.first == it_part->colour->second ){
line_colour.first = it_part->colour->first;
return true;
}
if( line_colour.second == it_part->colour->first ){
line_colour.second = it_part->colour->second;
return true;
}
return false;
}
//! Connect parton to u-channel colour line & update the line
//! returns false if connection not possible
template<class OutIterator>
bool try_connect_u(OutIterator & it_part, Colour & line_colour){
auto it_next = std::next(it_part);
if( try_connect_t(it_next, line_colour)
&& try_connect_t(it_part, line_colour)
){
it_part=it_next;
return true;
}
return false;
}
} // namespace
bool Event::is_leading_colour() const {
if( !correct_colour(incoming()[0]) || !correct_colour(incoming()[1]) )
return false;
Colour line_colour = *incoming()[0].colour;
std::swap(line_colour.first, line_colour.second);
// reasonable colour
if(!std::all_of(outgoing().cbegin(), outgoing().cend(), correct_colour))
return false;
for(auto it_part = cbegin_partons(); it_part!=cend_partons(); ++it_part){
switch (type()) {
case event_type::FKL:
if( !try_connect_t(it_part, line_colour) )
return false;
break;
case event_type::unob:
case event_type::qqbar_exb: {
if( !try_connect_t(it_part, line_colour)
// u-channel only allowed at impact factor
&& (std::distance(cbegin_partons(), it_part)!=0
|| !try_connect_u(it_part, line_colour)))
return false;
break;
}
case event_type::unof:
case event_type::qqbar_exf: {
if( !try_connect_t(it_part, line_colour)
// u-channel only allowed at impact factor
&& (std::distance(it_part, cend_partons())!=2
|| !try_connect_u(it_part, line_colour)))
return false;
break;
}
case event_type::qqbar_mid:{
auto it_next = std::next(it_part);
if( !try_connect_t(it_part, line_colour)
// u-channel only allowed at q-qbar/qbar-q pair
&& ( ( !(is_quark(*it_part) && is_antiquark(*it_next))
&& !(is_antiquark(*it_part) && is_quark(*it_next)))
|| !try_connect_u(it_part, line_colour))
)
return false;
break;
}
default:
throw std::logic_error{"unreachable"};
}
// no colour singlet exchange/disconnected diagram
if(line_colour.first == line_colour.second)
return false;
}
return (incoming()[1].colour->first == line_colour.first)
&& (incoming()[1].colour->second == line_colour.second);
}
namespace {
//! connect incoming Particle to colour flow
void connect_incoming(Particle & in, int & colour, int & anti_colour){
in.colour = std::make_pair(anti_colour, colour);
// gluon
if(in.type == pid::gluon)
return;
if(in.type > 0){
// quark
assert(is_quark(in));
in.colour->second = 0;
colour*=-1;
return;
}
// anti-quark
assert(is_antiquark(in));
in.colour->first = 0;
anti_colour*=-1;
}
//! connect outgoing Particle to t-channel colour flow
template<class OutIterator>
void connect_tchannel(
OutIterator & it_part, int & colour, int & anti_colour, RNG & ran
){
assert(colour>0 || anti_colour>0);
if(it_part->type == ParticleID::gluon){
// gluon
if(colour>0 && anti_colour>0){
// on g line => connect to colour OR anti-colour (random)
if(ran.flat() < 0.5){
it_part->colour = std::make_pair(colour+2,colour);
colour+=2;
} else {
it_part->colour = std::make_pair(anti_colour, anti_colour+2);
anti_colour+=2;
}
} else if(colour > 0){
// on q line => connect to available colour
it_part->colour = std::make_pair(colour+2, colour);
colour+=2;
} else {
assert(colour<0 && anti_colour>0);
// on qbar line => connect to available anti-colour
it_part->colour = std::make_pair(anti_colour, anti_colour+2);
anti_colour+=2;
}
} else if(is_quark(*it_part)) {
// quark
assert(anti_colour>0);
if(colour>0){
// on g line => connect and remove anti-colour
it_part->colour = std::make_pair(anti_colour, 0);
anti_colour+=2;
anti_colour*=-1;
} else {
// on qbar line => new colour
colour*=-1;
it_part->colour = std::make_pair(colour, 0);
}
} else if(is_antiquark(*it_part)) {
// anti-quark
assert(colour>0);
if(anti_colour>0){
// on g line => connect and remove colour
it_part->colour = std::make_pair(0, colour);
colour+=2;
colour*=-1;
} else {
// on q line => new anti-colour
anti_colour*=-1;
it_part->colour = std::make_pair(0, anti_colour);
}
} else { // not a parton
assert(!is_parton(*it_part));
it_part->colour = {};
}
}
//! connect to t- or u-channel colour flow
template<class OutIterator>
void connect_utchannel(
OutIterator & it_part, int & colour, int & anti_colour, RNG & ran
){
OutIterator it_first = it_part++;
if(ran.flat()<.5) {// t-channel
connect_tchannel(it_first, colour, anti_colour, ran);
connect_tchannel(it_part, colour, anti_colour, ran);
}
else { // u-channel
connect_tchannel(it_part, colour, anti_colour, ran);
connect_tchannel(it_first, colour, anti_colour, ran);
}
}
} // namespace
bool Event::generate_colours(RNG & ran){
// generate only for HEJ events
if(!event_type::is_resummable(type()))
return false;
assert(std::is_sorted(
begin(outgoing()), end(outgoing()), rapidity_less{}));
assert(incoming()[0].pz() < incoming()[1].pz());
// positive (anti-)colour -> can connect
// negative (anti-)colour -> not available/used up by (anti-)quark
int colour = COLOUR_OFFSET;
int anti_colour = colour+1;
// initialise first
connect_incoming(incoming_[0], colour, anti_colour);
// reset outgoing colours
std::for_each(outgoing_.begin(), outgoing_.end(),
[](Particle & part){ part.colour = {};});
for(auto it_part = begin_partons(); it_part!=end_partons(); ++it_part){
switch (type()) {
// subleading can connect to t- or u-channel
case event_type::unob:
case event_type::qqbar_exb: {
if( std::distance(begin_partons(), it_part)==0)
connect_utchannel(it_part, colour, anti_colour, ran);
else
connect_tchannel(it_part, colour, anti_colour, ran);
break;
}
case event_type::unof:
case event_type::qqbar_exf: {
if( std::distance(it_part, end_partons())==2)
connect_utchannel(it_part, colour, anti_colour, ran);
else
connect_tchannel(it_part, colour, anti_colour, ran);
break;
}
case event_type::qqbar_mid:{
auto it_next = std::next(it_part);
if( std::distance(begin_partons(), it_part)>0
&& std::distance(it_part, end_partons())>2
&& ( (is_quark(*it_part) && is_antiquark(*it_next))
|| (is_antiquark(*it_part) && is_quark(*it_next)) )
)
connect_utchannel(it_part, colour, anti_colour, ran);
else
connect_tchannel(it_part, colour, anti_colour, ran);
break;
}
default: // rest has to be t-channel
connect_tchannel(it_part, colour, anti_colour, ran);
}
}
// Connect last
connect_incoming(incoming_[1], anti_colour, colour);
assert(is_leading_colour());
return true;
} // generate_colours
namespace {
bool valid_parton(
std::vector<fastjet::PseudoJet> const & jets,
Particle const & parton, int const idx,
double const soft_pt_regulator, double const min_extparton_pt
){
// TODO code overlap with PhaseSpacePoint::pass_extremal_cuts
if(min_extparton_pt > parton.pt()) return false;
if(idx<0) return false;
assert(static_cast<int>(jets.size())>=idx);
auto const & jet{ jets[idx] };
return (parton.p - jet).pt()/jet.pt() <= soft_pt_regulator;
}
} // namespace
bool Event::valid_hej_state(double const soft_pt_regulator,
double const min_pt
) const {
using namespace event_type;
if(!is_resummable(type()))
return false;
auto const & jet_indices{ particle_jet_indices() };
auto jet_idx_begin{ jet_indices.cbegin() };
auto jet_idx_end{ jet_indices.crbegin() };
auto part_begin{ cbegin_partons() };
auto part_end{ crbegin_partons() };
if(!is_backward_g_to_h(*this)) {
const int first_jet_idx = *jet_idx_begin;
if(! valid_parton(jets(), *part_begin, first_jet_idx, soft_pt_regulator, min_pt)) {
return false;
}
++part_begin;
++jet_idx_begin;
// unob -> second parton in own jet
if( type() & (unob | qqbar_exb) ){
if(
(*jet_idx_begin == first_jet_idx)
|| !valid_parton(jets(), *part_begin, *jet_idx_begin, soft_pt_regulator, min_pt)
) {
return false;
}
++part_begin;
++jet_idx_begin;
}
}
if(!is_forward_g_to_h(*this)) {
const int last_jet_idx = *jet_idx_end;
if(!valid_parton(jets(), *part_end, last_jet_idx, soft_pt_regulator, min_pt)) {
return false;
}
++part_end;
++jet_idx_end;
if( type() & (unof | qqbar_exf) ){
if(
(*jet_idx_end == last_jet_idx)
|| !valid_parton(jets(), *part_end, *jet_idx_end, soft_pt_regulator, min_pt)
) {
return false;
}
++part_end;
// ++jet_idx_end; // last check, we don't need idx_end afterwards
}
}
if( type() & qqbar_mid ){
// find qqbar pair
auto begin_qqbar{ std::find_if( part_begin, part_end.base(),
[](Particle const & part) -> bool {
return part.type != ParticleID::gluon;
}
)};
assert(begin_qqbar != part_end.base());
long int qqbar_pos{ std::distance(part_begin, begin_qqbar) };
assert(qqbar_pos >= 0);
jet_idx_begin += qqbar_pos;
+ const int next_jet_idx = *std::next(jet_idx_begin);
+ const auto next_qqbar = std::next(begin_qqbar);
if(
- (*jet_idx_begin == *std::next(jet_idx_begin))
+ (*jet_idx_begin == next_jet_idx)
|| ! valid_parton(jets(), *begin_qqbar, *jet_idx_begin, soft_pt_regulator, min_pt)
- || ! valid_parton(jets(), *std::next(begin_qqbar), *std::next(jet_idx_begin), soft_pt_regulator, min_pt)
+ || ! valid_parton(jets(), *next_qqbar, next_jet_idx, soft_pt_regulator, min_pt)
) {
return false;
}
}
return true;
}
bool Event::valid_incoming() const{
for(std::size_t i=0; i < incoming_.size(); ++i){
if(!(HEJ::nearby_ep(std::abs(incoming_[i].pz()), incoming_[i].E(), TOL*incoming_[i].E())
&& (incoming_[i].pt()==0.)))
return false;
}
return true;
}
Event::ConstPartonIterator Event::begin_partons() const {
return cbegin_partons();
}
Event::ConstPartonIterator Event::cbegin_partons() const {
return {HEJ::is_parton, cbegin(outgoing()), cend(outgoing())};
}
Event::ConstPartonIterator Event::end_partons() const {
return cend_partons();
}
Event::ConstPartonIterator Event::cend_partons() const {
return {HEJ::is_parton, cend(outgoing()), cend(outgoing())};
}
Event::ConstReversePartonIterator Event::rbegin_partons() const {
return crbegin_partons();
}
Event::ConstReversePartonIterator Event::crbegin_partons() const {
return std::reverse_iterator<ConstPartonIterator>( cend_partons() );
}
Event::ConstReversePartonIterator Event::rend_partons() const {
return crend_partons();
}
Event::ConstReversePartonIterator Event::crend_partons() const {
return std::reverse_iterator<ConstPartonIterator>( cbegin_partons() );
}
Event::PartonIterator Event::begin_partons() {
return {HEJ::is_parton, begin(outgoing_), end(outgoing_)};
}
Event::PartonIterator Event::end_partons() {
return {HEJ::is_parton, end(outgoing_), end(outgoing_)};
}
Event::ReversePartonIterator Event::rbegin_partons() {
return std::reverse_iterator<PartonIterator>( end_partons() );
}
Event::ReversePartonIterator Event::rend_partons() {
return std::reverse_iterator<PartonIterator>( begin_partons() );
}
namespace {
void print_momentum(std::ostream & os, fastjet::PseudoJet const & part){
constexpr int prec = 6;
const std::streamsize orig_prec = os.precision();
os <<std::scientific<<std::setprecision(prec) << "["
<<std::setw(2*prec+1)<<std::right<< part.px() << ", "
<<std::setw(2*prec+1)<<std::right<< part.py() << ", "
<<std::setw(2*prec+1)<<std::right<< part.pz() << ", "
<<std::setw(2*prec+1)<<std::right<< part.E() << "]"<< std::fixed;
os.precision(orig_prec);
}
void print_colour(std::ostream & os, std::optional<Colour> const & col){
constexpr int width = 3;
if(!col)
os << "(no color)"; // American spelling for better alignment
else
os << "(" <<std::setw(width)<<std::right<< col->first
<< ", " <<std::setw(width)<<std::right<< col->second << ")";
}
} // namespace
std::ostream& operator<<(std::ostream & os, Event const & ev){
constexpr int prec = 4;
constexpr int wtype = 3; // width for types
const std::streamsize orig_prec = os.precision();
os <<std::setprecision(prec)<<std::fixed;
os << "########## " << name(ev.type()) << " ##########" << std::endl;
os << "Incoming particles:\n";
for(auto const & in: ev.incoming()){
os <<std::setw(wtype)<< in.type << ": ";
print_colour(os, in.colour);
os << " ";
print_momentum(os, in.p);
os << std::endl;
}
os << "\nOutgoing particles: " << ev.outgoing().size() << "\n";
for(auto const & out: ev.outgoing()){
os <<std::setw(wtype)<< out.type << ": ";
print_colour(os, out.colour);
os << " ";
print_momentum(os, out.p);
os << " => rapidity="
<<std::setw(2*prec-1)<<std::right<< out.rapidity() << std::endl;
}
os << "\nForming Jets: " << ev.jets().size() << "\n";
for(auto const & jet: ev.jets()){
print_momentum(os, jet);
os << " => rapidity="
<<std::setw(2*prec-1)<<std::right<< jet.rapidity() << std::endl;
}
if(!ev.decays().empty() ){
os << "\nDecays: " << ev.decays().size() << "\n";
for(auto const & decay: ev.decays()){
os <<std::setw(wtype)<< ev.outgoing()[decay.first].type
<< " (" << decay.first << ") to:\n";
for(auto const & out: decay.second){
os <<" "<<std::setw(wtype)<< out.type << ": ";
print_momentum(os, out.p);
os << " => rapidity="
<<std::setw(2*prec-1)<<std::right<< out.rapidity() << std::endl;
}
}
}
os << std::defaultfloat;
os.precision(orig_prec);
return os;
}
double shat(Event const & ev){
return (ev.incoming()[0].p + ev.incoming()[1].p).m2();
}
LHEF::HEPEUP to_HEPEUP(Event const & event, LHEF::HEPRUP * heprup){
LHEF::HEPEUP result;
result.heprup = heprup;
result.weights = {{event.central().weight, nullptr}};
for(auto const & var: event.variations()){
result.weights.emplace_back(var.weight, nullptr);
}
size_t num_particles = event.incoming().size() + event.outgoing().size();
for(auto const & decay: event.decays()) num_particles += decay.second.size();
result.NUP = num_particles;
// the following entries are pretty much meaningless
result.IDPRUP = event.type(); // event type
result.AQEDUP = 1./128.; // alpha_EW
//result.AQCDUP = 0.118 // alpha_QCD
// end meaningless part
result.XWGTUP = event.central().weight;
result.SCALUP = event.central().muf;
result.scales.muf = event.central().muf;
result.scales.mur = event.central().mur;
result.scales.SCALUP = event.central().muf;
result.pdfinfo.p1 = event.incoming().front().type;
result.pdfinfo.p2 = event.incoming().back().type;
result.pdfinfo.scale = event.central().muf;
result.IDUP.reserve(num_particles); // PID
result.ISTUP.reserve(num_particles); // status (in, out, decay)
result.PUP.reserve(num_particles); // momentum
result.MOTHUP.reserve(num_particles); // index mother particle
result.ICOLUP.reserve(num_particles); // colour
// incoming
std::array<Particle, 2> incoming{ event.incoming() };
// First incoming should be positive pz according to LHE standard
// (or at least most (everyone?) do it this way, and Pythia assumes it)
if(incoming[0].pz() < incoming[1].pz())
std::swap(incoming[0], incoming[1]);
for(Particle const & in: incoming){
result.IDUP.emplace_back(in.type);
result.ISTUP.emplace_back(LHE_Status::in);
result.PUP.push_back({in.p[0], in.p[1], in.p[2], in.p[3], in.p.m()});
result.MOTHUP.emplace_back(0, 0);
assert(in.colour);
result.ICOLUP.emplace_back(*in.colour);
}
// outgoing
for(size_t i = 0; i < event.outgoing().size(); ++i){
Particle const & out = event.outgoing()[i];
result.IDUP.emplace_back(out.type);
const int status = event.decays().count(i) != 0u
?LHE_Status::decay
:LHE_Status::out;
result.ISTUP.emplace_back(status);
result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
result.MOTHUP.emplace_back(1, 2);
if(out.colour)
result.ICOLUP.emplace_back(*out.colour);
else{
result.ICOLUP.emplace_back(std::make_pair(0,0));
}
}
// decays
for(auto const & decay: event.decays()){
for(auto const & out: decay.second){
result.IDUP.emplace_back(out.type);
result.ISTUP.emplace_back(LHE_Status::out);
result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
const size_t mother_idx = 1 + event.incoming().size() + decay.first;
result.MOTHUP.emplace_back(mother_idx, mother_idx);
result.ICOLUP.emplace_back(0,0);
}
}
assert(result.ICOLUP.size() == num_particles);
static constexpr double unknown_spin = 9.; //per Les Houches accord
result.VTIMUP = std::vector<double>(num_particles, unknown_spin);
result.SPINUP = result.VTIMUP;
return result;
}
} // namespace HEJ

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