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test_colours.cc
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test_colours.cc
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/**
* \authors The HEJ collaboration (see AUTHORS for details)
* \date 2019-2020
* \copyright GPLv2 or later
*/
#include "hej_test.hh"
#include <cstdlib>
#include <iostream>
#include <utility>
#include <vector>
#include "HEJ/Constants.hh"
#include "HEJ/Event.hh"
#include "HEJ/event_types.hh"
#include "HEJ/exceptions.hh"
#include "HEJ/Particle.hh"
#include "HEJ/PDG_codes.hh"
#include "HEJ/RNG.hh"
#include "fastjet/JetDefinition.hh"
/// biased RNG to connect always to colour
class dum_rnd: public HEJ::DefaultRNG {
public:
dum_rnd() = default;
double flat() override {
return 0.;
}
};
HEJ::Event::EventData decay_boson( HEJ::Event::EventData ev ){
for( std::size_t i=0; i<ev.outgoing.size(); ++i ){
if( std::abs(ev.outgoing[i].type) == HEJ::ParticleID::Wp){
ev.decays[i] = decay_W(ev.outgoing[i]);
}
}
return ev;
}
void dump_event(HEJ::Event const & ev){
for(auto const & in: ev.incoming()){
std::cerr << "in type=" << in.type
<< ", colour={" << (*in.colour).first
<< ", " << (*in.colour).second << "}\n";
}
for(auto const & out: ev.outgoing()){
std::cerr << "out type=" << out.type << ", colour={";
if(out.colour)
std::cerr << (*out.colour).first << ", " << (*out.colour).second;
else
std::cerr << "non, non";
std::cerr << "}\n";
}
}
/// true if colour is allowed for particle
bool correct_colour(HEJ::Particle const & part){
if(!HEJ::is_parton(part) && !part.colour) return true;
if(!part.colour) return false;
int const colour = part.colour->first;
int const anti_colour = part.colour->second;
if(part.type == HEJ::ParticleID::gluon)
return colour != anti_colour
&& colour >= HEJ::COLOUR_OFFSET
&& anti_colour >= HEJ::COLOUR_OFFSET;
if(HEJ::is_quark(part))
return anti_colour == 0 && colour >= HEJ::COLOUR_OFFSET;
return colour == 0 && anti_colour >= HEJ::COLOUR_OFFSET;
}
bool correct_colour(HEJ::Event const & ev){
if(!ev.is_leading_colour())
return false;
// some of these additional checks are also in ev.is_leading_colour()
for(auto const & part: ev.incoming()){
if(!correct_colour(part))
return false;
}
for(auto const & part: ev.outgoing()){
if(!correct_colour(part))
return false;
}
return true;
}
bool match_expected(
HEJ::Event const & ev,
std::vector<HEJ::Colour> const & expected
){
ASSERT(ev.outgoing().size()+2==expected.size());
for(std::size_t i=0; i<ev.incoming().size(); ++i){
ASSERT(ev.incoming()[i].colour);
if( *ev.incoming()[i].colour != expected[i])
return false;
}
for(std::size_t i=2; i<ev.outgoing().size()+2; ++i){
if( ev.outgoing()[i-2].colour ){
if( *ev.outgoing()[i-2].colour != expected[i] )
return false;
} else if( expected[i].first != 0 || expected[i].second != 0)
return false;
}
return true;
}
void check_event(
HEJ::Event::EventData unc_ev,
std::vector<HEJ::Colour> const & expected_colours
){
unc_ev = decay_boson(std::move(unc_ev));
shuffle_particles(unc_ev); // make sure incoming order doesn't matter
HEJ::Event ev{unc_ev.cluster(
fastjet::JetDefinition(fastjet::JetAlgorithm::antikt_algorithm, 0.4), 30.)
};
ASSERT(HEJ::event_type::is_resummable(ev.type()));
dum_rnd rng;
ASSERT(!ev.is_leading_colour());
ASSERT(ev.generate_colours(rng));
if(!correct_colour(ev)){
std::cerr << "Found illegal colours for event\n";
dump_event(ev);
throw std::invalid_argument("Illegal colour set");
}
if(!match_expected(ev, expected_colours)){
std::cerr << "Colours didn't match expectation. Found\n";
dump_event(ev);
std::cerr << "but expected\n";
for(auto const & col: expected_colours){
std::cerr << "colour={" << col.first << ", " << col.second << "}\n";
}
throw std::logic_error("Colours did not match expectation");
}
}
HEJ::Event::EventData reset_colour(
HEJ::Event::EventData ev, std::vector<HEJ::Colour> const & goal
){
for(std::size_t i=0; i<2; ++i){
ev.incoming[i].colour = goal[i];
}
for(std::size_t i=0; i<ev.outgoing.size(); ++i){
auto const & col_goal{ goal[i+2] };
if(col_goal.first == 0 && col_goal.second == 0)
ev.outgoing[i].colour = HEJ::optional<HEJ::Colour>{};
else
ev.outgoing[i].colour = col_goal;
}
return ev;
}
int main() {
HEJ::Event::EventData ev;
std::vector<HEJ::Colour> expected_colours(7);
/// pure gluon (they all have a mass of 4 GeV to allow decays)
ev.incoming[0] = { HEJ::ParticleID::gluon, { 0, 0, -205, 205}, {}};
ev.incoming[1] = { HEJ::ParticleID::gluon, { 0, 0, 279, 279}, {}};
ev.outgoing.push_back({ HEJ::ParticleID::gluon, {-15, -82, -82, 117}, {}});
ev.outgoing.push_back({ HEJ::ParticleID::gluon, { 68, 93, 20, 117}, {}});
ev.outgoing.push_back({ HEJ::ParticleID::higgs, {-30, -65, 22, 75}, {}});
ev.outgoing.push_back({ HEJ::ParticleID::gluon, {-12, 92, 76, 120}, {}});
ev.outgoing.push_back({ HEJ::ParticleID::gluon, {-11, -38, 38, 55}, {}});
expected_colours[0] = {502, 501};
expected_colours[1] = {509, 502};
expected_colours[2] = {503, 501};
expected_colours[3] = {505, 503};
expected_colours[4] = { 0, 0};
expected_colours[5] = {507, 505};
expected_colours[6] = {509, 507};
// default colours is always forbidden!
// default: swap last two (anti-)colour -> crossing
ev=reset_colour(ev, expected_colours);
std::swap(ev.outgoing[4].colour, ev.outgoing[3].colour);
check_event(ev, expected_colours);
/// last g to Qx (=> gQx -> g ... Qx)
ev.incoming[1].type = HEJ::ParticleID::d_bar;
ev.outgoing[4].type = HEJ::ParticleID::d_bar;
// => only end changes
expected_colours[1].first = 0;
expected_colours[6].first = 0;
// default: swap last two anti-colours -> last gluon colour singlet
ev=reset_colour(ev, expected_colours);
std::swap(ev.outgoing[4].colour->second, ev.outgoing[3].colour->second);
check_event(ev, expected_colours);
{
// don't overwrite
auto new_expected = expected_colours;
auto new_ev = ev;
/// uno forward (=> gQx -> g ... Qx g)
std::swap(new_ev.outgoing[3].type, new_ev.outgoing[4].type);
// => uno quarks eats colour and gluon connects to anti-colour
new_expected[5] = {0, expected_colours[3].first};
new_expected[6] = {expected_colours[0].first, expected_colours[0].first+2};
new_expected[1].second += 2; // one more anti-colour in line
// default: swap last two anti-colours -> crossing
new_ev=reset_colour(new_ev, new_expected);
std::swap(new_ev.outgoing[4].colour->second, new_ev.outgoing[3].colour->second);
check_event(new_ev, new_expected);
}
/// swap Qx <-> Q (=> gQ -> g ... Q)
ev.incoming[1].type = HEJ::ParticleID::d;
ev.outgoing[4].type = HEJ::ParticleID::d;
// => swap: colour<->anti && initial<->final
std::swap(expected_colours[1], expected_colours[6]);
std::swap(expected_colours[1].first, expected_colours[1].second);
std::swap(expected_colours[6].first, expected_colours[6].second);
// default: swap incoming <-> outgoing
ev=reset_colour(ev, expected_colours);
std::swap(ev.incoming[0].colour, ev.outgoing[0].colour);
check_event(ev, expected_colours);
/// first g to qx (=> qxQ -> qx ... Q)
ev.incoming[0].type = HEJ::ParticleID::u_bar;
ev.outgoing[0].type = HEJ::ParticleID::u_bar;
expected_colours[0] = { 0, 501};
// => shift anti-colour index one up
expected_colours[1].first -= 2;
expected_colours[5] = expected_colours[3];
expected_colours[3] = expected_colours[2];
expected_colours[2] = { 0, 502};
// default: closed qx->qx g
ev=reset_colour(ev, expected_colours);
ev.outgoing[1].colour->first = ev.outgoing[0].colour->second;
ev.outgoing[1].colour->second = ev.incoming[0].colour->second;
ev.outgoing[4].colour->first = ev.outgoing[3].colour->second;
check_event(ev, expected_colours);
{
// don't overwrite
auto new_expected = expected_colours;
auto new_ev = ev;
/// uno backward (=> qxQ -> g qx ... Q)
std::swap(new_ev.outgoing[0].type, new_ev.outgoing[1].type);
// => uno gluon connects to quark colour
new_expected[3] = expected_colours[2];
new_expected[2] = {expected_colours[0].second+2, expected_colours[0].second};
// default: Colourful Higgs
new_ev=reset_colour(new_ev, new_expected);
new_ev.outgoing[2].colour = std::make_pair(1,1);
check_event(new_ev, new_expected);
/// swap qx <-> q (=> qQ -> g q ... Q)
new_ev.incoming[0].type = HEJ::ParticleID::u;
new_ev.outgoing[1].type = HEJ::ParticleID::u;
// => swap: colour<->anti && inital<->final
std::swap(new_expected[0], new_expected[3]);
std::swap(new_expected[0].first, new_expected[0].second);
std::swap(new_expected[3].first, new_expected[3].second);
// => & connect first gluon with remaining anti-colour
new_expected[2] = {new_expected[0].first, new_expected[0].first+2};
// shift colour line one down
new_expected[1].first-=2;
new_expected[5].first-=2;
new_expected[5].second-=2;
// shift anti-colour line one up
new_expected[6].first+=2;
// default: swap 2 quarks -> disconnected
new_ev=reset_colour(new_ev, new_expected);
std::swap(new_ev.outgoing[1].colour, new_ev.outgoing[4].colour);
check_event(new_ev, new_expected);
}
{
// don't overwrite
auto new_expected = expected_colours;
auto new_ev = ev;
/// uno forward (=> qxQ -> qx ... Q g)
std::swap(new_ev.outgoing[3].type, new_ev.outgoing[4].type);
// => uno gluon connects to remaining colour
new_expected[5] = expected_colours[6];
new_expected[6] = {expected_colours[3].first+2, expected_colours[3].first};
// default: no colour on last gluon
new_ev=reset_colour(new_ev, new_expected);
new_ev.incoming[1].colour->first = new_ev.outgoing[4].colour->second;
new_ev.outgoing[4].colour = {};
check_event(new_ev, new_expected);
}
{
// don't overwrite
auto new_expected = expected_colours;
auto new_ev = ev;
/// qqx backward (=> gQ -> qx q ... Q) with Wp
// => swap: incoming q <-> outgoing gluon
std::swap(new_ev.incoming[0].type, new_ev.outgoing[1].type);
new_ev.outgoing[1].type=static_cast<HEJ::ParticleID>(
-(new_ev.outgoing[1].type+1) );
new_ev.outgoing[2].type = HEJ::ParticleID::Wp;
// incoming q -> outgoing q (colour<->anti)
std::swap(new_expected[0], new_expected[3]);
std::swap(new_expected[3].first, new_expected[3].second);
new_expected[3].first+=2;
new_expected[0].first-=1; // skip one index
// couple first in to first out
new_expected[2].second=new_expected[0].second;
// default: swap qqx <-> first g
new_ev=reset_colour(new_ev, new_expected);
std::swap(new_ev.outgoing[0].colour->second, new_ev.outgoing[3].colour->second);
std::swap(new_ev.outgoing[1].colour->first, new_ev.outgoing[3].colour->first);
check_event(new_ev, new_expected);
}
{
// don't overwrite
auto new_expected = expected_colours;
auto new_ev = ev;
/// qqx forward (=> qx g -> qx ... Qx Q) with Wp
// => swap: incoming Q <-> outgoing gluon
std::swap(new_ev.incoming[1].type, new_ev.outgoing[3].type);
new_ev.outgoing[3].type=static_cast<HEJ::ParticleID>(
-(new_ev.outgoing[3].type+1));
new_ev.outgoing[2].type = HEJ::ParticleID::Wp;
// incoming q -> outgoing q (colour<->anti)
std::swap(new_expected[1], new_expected[5]);
std::swap(new_expected[5].first, new_expected[5].second);
new_expected[5].second-=2;
new_expected[1].second-=1; // skip one index
// couple last in to last out
new_expected[6].first=new_expected[1].first;
// default: uncoloured quark
new_ev=reset_colour(new_ev, new_expected);
new_ev.outgoing[0].colour = {};
check_event(new_ev, new_expected);
// move Higgs to position 1 (=> qx g -> qx h g Qx Q)
std::swap(new_ev.outgoing[1].type, new_ev.outgoing[2].type);
std::swap(new_expected[3], new_expected[4]); // trivial
// default: incoming qx wrong colour
new_ev=reset_colour(new_ev, new_expected);
new_ev.incoming[0].colour->first = 1;
check_event(new_ev, new_expected);
// central qqx (=> qx g -> qx h Q Qx g)
// => swap: Q <-> g
std::swap(new_ev.outgoing[2].type, new_ev.outgoing[4].type);
std::swap(new_expected[4], new_expected[6]);
// gluon was connected on left side, i.e. doesn't matter for QQx
// => couple Q to out qx
new_expected[4].first = new_expected[2].second;
// Qx next in line
new_expected[5].second = new_expected[4].first+2;
// incoming g shifted by one position in line
new_expected[1].first-=2;
new_expected[1].second+=2;
// default: wrong colour in last incoming
new_ev=reset_colour(new_ev, new_expected);
std::swap(new_ev.incoming[1].colour->first,
new_ev.incoming[1].colour->second);
check_event(new_ev, new_expected);
}
return EXIT_SUCCESS;
}

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