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diff --git a/src/Event.cc b/src/Event.cc
index 33a291a..ba02818 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -1,1178 +1,1179 @@
/**
* \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 <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/PDG_codes.hh"
#include "HEJ/RNG.hh"
#include "HEJ/exceptions.hh"
#include "HEJ/optional.hh"
namespace HEJ {
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]);
}
/// @name helper functions to determine event type
//@{
/**
* \brief check if final state valid for HEJ
*
* 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(Event const & ev){
std::vector<Particle> const & outgoing = ev.outgoing();
if(ev.decays().size() > 1) // at most one decay
return false;
bool has_AWZH_boson = false;
for( size_t i=0; i<outgoing.size(); ++i ){
auto const & out{ outgoing[i] };
if(is_AWZH_boson(out.type)){
// at most one boson
if(has_AWZH_boson) return false;
has_AWZH_boson = true;
// valid decay for W
if(std::abs(out.type) == ParticleID::Wp){
// exactly 1 decay of W
if( ev.decays().size() != 1 || ev.decays().cbegin()->first != i )
return false;
if( !valid_W_decay(out.type>0?+1:-1, ev.decays().cbegin()->second) )
return false;
}
// valid decay for Z
if(out.type == ParticleID::Z_photon_mix){
// exactly 1 decay
if( ev.decays().size() != 1 || ev.decays().cbegin()->first != i )
return false;
if( !valid_Z_decay(ev.decays().cbegin()->second) )
return false;
}
}
else if(! is_parton(out.type)) return false;
}
return true;
}
/**
* returns all EventTypes implemented in HEJ
*/
size_t implemented_types(std::vector<Particle> const & bosons){
using namespace event_type;
if(bosons.empty()) return FKL | unob | unof | qqxexb | qqxexf | qqxmid;
if(bosons.size()>1) return non_resummable; // multi boson
switch (bosons[0].type) {
case ParticleID::Wp:
case ParticleID::Wm:
return FKL | unob | unof | qqxexb | qqxexf | qqxmid;
case ParticleID::Z_photon_mix:
return FKL | unob | unof;
case ParticleID::h:
return FKL | unob | unof;
default:
return non_resummable;
}
}
/**
* \brief function which determines if type change is consistent with Wp emission.
* @param in incoming Particle id
* @param out outgoing Particle id
* @param qqx Current both incoming/both outgoing?
*
* \see is_Wm_Change
*/
bool is_Wp_Change(ParticleID in, ParticleID out, bool qqx){
if(!qqx && (in==-1 || in== 2 || in==-3 || in== 4)) return out== (in-1);
if( qqx && (in== 1 || in==-2 || in== 3 || in==-4)) 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 qqx Current both incoming/both outgoing?
*
* Ensures that change type of quark line is possible by a flavour changing
* Wm emission. Allows checking of qqx currents also.
*/
bool is_Wm_Change(ParticleID in, ParticleID out, bool qqx){
if(!qqx && (in== 1 || in==-2 || in== 3 || in==-4)) return out== (in+1);
if( qqx && (in==-1 || in== 2 || in==-3 || in== 4)) 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 qqx Current both incoming/outgoing?
*/
bool no_flavour_change(ParticleID in, ParticleID out, bool qqx){
const int qqxCurrent = qqx?-1:1;
if(std::abs(in)<=pid::top || in==pid::gluon)
return (in==out*qqxCurrent);
return false;
}
bool has_2_jets(Event const & event){
return event.jets().size() >= 2;
}
/**
* \brief check if we have a valid Impact factor
* @param in incoming Particle
* @param out outgoing Particle
* @param qqx 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 qqx, int & W_change
){
if( no_flavour_change(in, out, qqx) ){
return true;
}
if( is_Wp_Change(in, out, qqx) ) {
W_change+=1;
return true;
}
if( is_Wm_Change(in, out, qqx) ) {
W_change-=1;
return true;
}
return false;
}
//! 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;
assert(boson.size() < 2);
// keep track of all states that we don't test
size_t not_tested = qqxmid;
if(backward)
not_tested |= unof | qqxexf;
else
not_tested |= unob | qqxexb;
// Is this LL current?
if( is_valid_impact_factor(incoming_id, begin_out->type, false, W_change) ){
++begin_out;
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 qqx
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?qqxexb:qqxexf);
}
}
}
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;
assert(boson.size() < 2);
// 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
| qqxexb | qqxexf;
// Find the first non-gluon/non-FKL
while( (begin_out->type==pid::gluon) && (begin_out!=end_out) ){
++begin_out;
}
// 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( is_valid_impact_factor(
begin_out->type, next->type, true, W_change )
){
// veto Higgs inside qqx
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 gluon/FKL
for(; begin_out!=end_out; ++begin_out){
if(begin_out->type != pid::gluon) return non_resummable;
}
return possible | qqxmid;
}
return non_resummable;
}
/**
* \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_2_jets(ev))
return no_2_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{ev.cbegin_partons()};
auto end_out{ev.crbegin_partons()};
assert(std::distance(begin(in), end(in)) == 2);
assert(std::distance(begin_out, end_out.base()) >= 2);
assert(std::is_sorted(begin_out, end_out.base(), rapidity_less{}));
auto const boson{ filter_AWZH_bosons(ev.outgoing()) };
// we only allow one boson through final_state_ok
assert(boson.size()<=1);
// keep track of potential W couplings, at the end the sum should be 0
int remaining_Wp = 0;
int remaining_Wm = 0;
if(!boson.empty() && std::abs(boson.front().type) == ParticleID::Wp ){
if(boson.front().type>0) ++remaining_Wp;
else ++remaining_Wm;
}
int W_change = 0;
size_t final_type = ~(no_2_jets | bad_final_state);
// check forward impact factor
final_type &= possible_impact_factors(
in.front().type,
begin_out, end_out.base(),
W_change, boson, 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;
W_change = 0;
// check backward impact factor
final_type &= possible_impact_factors(
in.back().type,
end_out, std::make_reverse_iterator(begin_out),
W_change, boson, 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;
W_change = 0;
// check central emissions
final_type &= possible_central(
begin_out, end_out.base(), W_change, boson );
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(boson)) != 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]: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 {
Particle reconstruct_boson(std::vector<Particle> const & leptons) {
Particle decayed_boson;
decayed_boson.p = leptons[0].p + leptons[1].p;
const int pidsum = leptons[0].type + leptons[1].type;
if(pidsum == +1) {
assert(is_antilepton(leptons[0]));
if(is_antineutrino(leptons[0])) {
throw not_implemented{"lepton-flavour violating final state"};
}
assert(is_neutrino(leptons[1]));
// charged antilepton + neutrino means we had a W+
decayed_boson.type = pid::Wp;
}
else if(pidsum == -1) {
assert(is_antilepton(leptons[0]));
if(is_neutrino(leptons[1])) {
throw not_implemented{"lepton-flavour violating final state"};
}
assert(is_antineutrino(leptons[0]));
// charged lepton + antineutrino means we had a W-
decayed_boson.type = pid::Wm;
}
else if(pidsum == 0) {
assert(is_anylepton(leptons[0]));
if(is_anyneutrino(leptons[0])) {
throw not_implemented{"final state with two neutrinos"};
}
// charged lepton-antilepton pair means we had a Z/photon
decayed_boson.type = pid::Z_photon_mix;
}
else {
throw not_implemented{
"final state with leptons "
+ name(leptons[0].type)
+ " and "
+ name(leptons[1].type)
};
}
return decayed_boson;
}
} // namespace
void Event::EventData::reconstruct_intermediate() {
const auto begin_leptons = std::partition(
begin(outgoing), end(outgoing),
[](Particle const & p) {return !is_anylepton(p);}
);
- if(begin_leptons == end(outgoing)) return;
- assert(is_anylepton(*begin_leptons));
+ // We can only reconstruct FS with 2 leptons
+ if(std::distance(begin_leptons, end(outgoing)) != 2) return;
std::vector<Particle> leptons(begin_leptons, end(outgoing));
- outgoing.erase(begin_leptons, end(outgoing));
- if(leptons.size() != 2) {
- throw not_implemented{"Final states with one or more than two leptons"};
- }
std::sort(
begin(leptons), end(leptons),
[](Particle const & p0, Particle const & p1) {
+ assert(is_anylepton(p0) && is_anylepton(p1));
return p0.type < p1.type;
}
);
- outgoing.emplace_back(reconstruct_boson(leptons));
+ // `reconstruct_boson` can throw, it should therefore be called before
+ // changing `outgoing` to allow the user to recover the original EventData
+ auto boson = reconstruct_boson(leptons);
+ outgoing.erase(begin_leptons, end(outgoing));
+ outgoing.emplace_back(std::move(boson));
decays.emplace(outgoing.size()-1, std::move(leptons));
}
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::qqxexb: {
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::qqxexf: {
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::qqxmid:{
auto it_next = std::next(it_part);
if( !try_connect_t(it_part, line_colour)
// u-channel only allowed at qqx/qxq 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 qx 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 qx 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::qqxexb: {
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::qqxexf: {
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::qqxmid:{
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 max_ext_soft_pt_fraction, 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() <= max_ext_soft_pt_fraction;
}
} // namespace
// this should work with multiple types
bool Event::valid_hej_state(double const max_frac,
double const min_pt
) const {
using namespace event_type;
if(!is_resummable(type()))
return false;
auto const & jet_idx{ particle_jet_indices() };
auto idx_begin{ jet_idx.cbegin() };
auto idx_end{ jet_idx.crbegin() };
auto part_begin{ cbegin_partons() };
auto part_end{ crbegin_partons() };
// always seperate extremal jets
if( !valid_parton(jets(), *part_begin, *idx_begin, max_frac, min_pt) )
return false;
++part_begin;
++idx_begin;
if( !valid_parton(jets(), *part_end, *idx_end, max_frac, min_pt) )
return false;
++part_end;
++idx_end;
// unob -> second parton in own jet
if( type() & (unob | qqxexb) ){
if( !valid_parton(jets(), *part_begin, *idx_begin, max_frac, min_pt) )
return false;
++part_begin;
++idx_begin;
}
if( type() & (unof | qqxexf) ){
if( !valid_parton(jets(), *part_end, *idx_end, max_frac, min_pt) )
return false;
++part_end;
// ++idx_end; // last check, we don't need idx_end afterwards
}
if( type() & qqxmid ){
// find qqx pair
auto begin_qqx{ std::find_if( part_begin, part_end.base(),
[](Particle const & part) -> bool {
return part.type != ParticleID::gluon;
}
)};
assert(begin_qqx != part_end.base());
long int qqx_pos{ std::distance(part_begin, begin_qqx) };
assert(qqx_pos >= 0);
idx_begin+=qqx_pos;
if( !( valid_parton(jets(),*begin_qqx, *idx_begin, max_frac,min_pt)
&& valid_parton(jets(),*(++begin_qqx),*(++idx_begin),max_frac,min_pt)
))
return false;
}
return true;
}
Event::ConstPartonIterator Event::begin_partons() const {
return cbegin_partons();
}
Event::ConstPartonIterator Event::cbegin_partons() const {
return boost::make_filter_iterator(
static_cast<bool (*)(Particle const &)>(is_parton),
cbegin(outgoing()),
cend(outgoing())
);
}
Event::ConstPartonIterator Event::end_partons() const {
return cend_partons();
}
Event::ConstPartonIterator Event::cend_partons() const {
return boost::make_filter_iterator(
static_cast<bool (*)(Particle const &)>(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 boost::make_filter_iterator(
static_cast<bool (*)(Particle const &)>(is_parton),
begin(outgoing_),
end(outgoing_)
);
}
Event::PartonIterator Event::end_partons() {
return boost::make_filter_iterator(
static_cast<bool (*)(Particle const &)>(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, 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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