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diff --git a/src/EventReweighter.cc b/src/EventReweighter.cc
index 3ac852f..880028e 100644
--- a/src/EventReweighter.cc
+++ b/src/EventReweighter.cc
@@ -1,319 +1,320 @@
#include "RHEJ/EventReweighter.hh"
#include <string>
#include <unordered_map>
#include "RHEJ/PhaseSpacePoint.hh"
#include "RHEJ/PDG_codes.hh"
#include "RHEJ/config.hh" // ScaleGenerator definition
#include "RHEJ/debug.hh"
namespace RHEJ{
using EventType = event_type::EventType;
namespace {
static_assert(
std::numeric_limits<double>::has_quiet_NaN,
"no quiet NaN for double"
);
constexpr double NaN = std::numeric_limits<double>::quiet_NaN();
UnclusteredEvent to_UnclusteredEvent(PhaseSpacePoint const & psp){
UnclusteredEvent result;
result.incoming = psp.incoming();
std::sort(
begin(result.incoming), end(result.incoming),
[](Sparticle o1, Sparticle o2){return o1.p.pz()<o2.p.pz();}
);
assert(result.incoming.size() == 2);
result.outgoing = psp.outgoing();
assert(
std::is_sorted(
begin(result.outgoing), end(result.outgoing),
rapidity_less{}
)
);
assert(result.outgoing.size() >= 2);
result.decays = psp.decays();
result.central.mur = NaN;
result.central.muf = NaN;
result.central.weight = psp.weight();
return result;
}
} // anonymous namespace
EventReweighter::EventReweighter(
LHEF::HEPRUP const & heprup,
fastjet::JetDefinition jet_def, double jetptmin,
EventTreatMap treat,
double extpartonptmin, double max_ext_soft_pt_fraction,
bool log_corr,
HiggsCouplingSettings Higgs_coupling
):
EventReweighter{
RHEJ::Beam{
heprup.EBMUP.first,
{{
static_cast<RHEJ::ParticleID>(heprup.IDBMUP.first),
static_cast<RHEJ::ParticleID>(heprup.IDBMUP.second)
}}
},
heprup.PDFSUP.first,
jet_def, jetptmin,
std::move(treat),
extpartonptmin, max_ext_soft_pt_fraction,
log_corr,
std::move(Higgs_coupling)
}
{
if(heprup.EBMUP.second != E_beam_){
throw std::invalid_argument(
"asymmetric beam: " + std::to_string(E_beam_)
+ " ---> <--- " + std::to_string(heprup.EBMUP.second)
);
};
if(heprup.PDFSUP.second != pdf_.id()){
throw std::invalid_argument(
"conflicting PDF ids: " + std::to_string(pdf_.id())
+ " vs. " + std::to_string(heprup.PDFSUP.second)
);
}
}
EventReweighter::EventReweighter(
Beam beam,
int pdf_id,
fastjet::JetDefinition jet_def, double jetptmin,
EventTreatMap treat,
double extpartonptmin, double max_ext_soft_pt_fraction,
bool log_corr,
HiggsCouplingSettings Higgs_coupling
):
extpartonptmin_{extpartonptmin},
max_ext_soft_pt_fraction_{max_ext_soft_pt_fraction},
jetptmin_{jetptmin},
E_beam_{beam.E},
jet_def_{jet_def},
pdf_{pdf_id, beam.type.front(), beam.type.back()},
MEt2_{
[this](double mu){ return pdf_.Halphas(mu); },
jet_def, jetptmin,
log_corr, std::move(Higgs_coupling)
},
treat_{std::move(treat)}
{}
PDF const & EventReweighter::pdf() const{
return pdf_;
}
namespace{
static_assert(
std::numeric_limits<double>::has_infinity, "infinity not supported"
);
// there is no simple way to create a vector of move-only objects
// this is a clumsy work-around
ScaleGenerator make_identity(){
std::vector<std::unique_ptr<ScaleFunction>> scale_fun;
scale_fun.emplace_back(new InputScales);
return ScaleGenerator{
ScaleConfig{
std::move(scale_fun), {}, std::numeric_limits<double>::infinity()
}
};
}
const ScaleGenerator identity{make_identity()};
}
std::vector<Event> EventReweighter::reweight(
Event const & input_ev, int num_events
){
return reweight(input_ev, num_events, identity);
}
std::vector<Event> EventReweighter::reweight(
Event const & input_ev, int num_events,
ScaleGenerator const & gen_scales
){
auto res_events = gen_res_events(input_ev, num_events);
if(res_events.empty()) return {};
for(auto & event: res_events) event = gen_scales(event);
return rescale(input_ev, std::move(res_events));
}
/**
* \brief main generation/reweighting function: generate phase space points and divide out Born factors
*/
std::vector<Event> EventReweighter::gen_res_events(
Event const & ev,
int phase_space_points
){
assert(ev.variations().empty());
switch(treat_.at(ev.type())){
case EventTreatment::discard: return {};
case EventTreatment::keep:
if(! jets_pass_resummation_cuts(ev)) return {};
else return {ev};
default:;
}
const double Born_shat = shat(ev);
std::vector<Event> resummation_events;
for(int psp_number = 0; psp_number < phase_space_points; ++psp_number){
PhaseSpacePoint psp{
ev,
jet_def_, jetptmin_,
extpartonptmin_, max_ext_soft_pt_fraction_
};
if(psp.weight() == 0.) continue;
+ if(psp.incoming()[0].E() > E_beam_ || psp.incoming()[1].E() > E_beam_) continue;
resummation_events.emplace_back(
to_UnclusteredEvent(std::move(psp)), jet_def_, jetptmin_
);
auto & new_event = resummation_events.back();
assert(new_event.variations().empty());
new_event.central().mur = ev.central().mur;
new_event.central().muf = ev.central().muf;
const double resum_shat = shat(new_event);
new_event.central().weight *= ev.central().weight*Born_shat*Born_shat/
(phase_space_points*resum_shat*resum_shat);
}
return resummation_events;
}
std::vector<Event> EventReweighter::rescale(
Event const & Born_ev,
std::vector<Event> events
) const{
const double Born_pdf = pdf_factors(Born_ev).central;
const double Born_ME = tree_matrix_element(Born_ev);
for(auto & cur_event: events){
const auto pdf = pdf_factors(cur_event);
assert(pdf.variations.size() == cur_event.variations().size());
const auto ME = matrix_elements(cur_event);
assert(ME.variations.size() == cur_event.variations().size());
cur_event.central().weight *= pdf.central*ME.central/(Born_pdf*Born_ME);
for(size_t i = 0; i < cur_event.variations().size(); ++i){
cur_event.variations(i).weight *=
pdf.variations[i]*ME.variations[i]/(Born_pdf*Born_ME);
}
}
return events;
};
bool EventReweighter::jets_pass_resummation_cuts(
Event const & ev
) const{
const auto out_as_PseudoJet = to_PseudoJet(filter_partons(ev.outgoing()));
fastjet::ClusterSequence cs{out_as_PseudoJet, jet_def_};
return cs.inclusive_jets(jetptmin_).size() == ev.jets().size();
}
EventReweighter::EventFactors
EventReweighter::pdf_factors(Event const & ev) const{
auto const & a = ev.incoming().front();
auto const & b = ev.incoming().back();
const double xa = a.p.e()/E_beam_;
const double xb = b.p.e()/E_beam_;
EventFactors result;
std::unordered_map<double, double> known_pdf;
result.central =
pdf_.pdfpt(0,xa,ev.central().muf,a.type)*
pdf_.pdfpt(1,xb,ev.central().muf,b.type);
known_pdf.emplace(ev.central().muf, result.central);
result.variations.reserve(ev.variations().size());
for(auto const & param: ev.variations()){
const double muf = param.muf;
auto cur_pdf = known_pdf.find(muf);
if(cur_pdf == known_pdf.end()){
cur_pdf = known_pdf.emplace(
muf,
pdf_.pdfpt(0,xa,muf,a.type)*pdf_.pdfpt(1,xb,muf,b.type)
).first;
}
result.variations.emplace_back(cur_pdf->second);
}
assert(result.variations.size() == ev.variations().size());
return result;
}
EventReweighter::EventFactors
EventReweighter::matrix_elements(Event const & ev) const{
assert(treat_.count(ev.type()) > 0);
if(treat_.find(ev.type())->second == EventTreatment::keep){
return fixed_order_scale_ME(ev);
}
// precompute overall kinematic factor
const double ME_kin = MEt2_.tree_kin(ev.incoming(), ev.outgoing(), true);
EventFactors result;
std::unordered_map<double, double> known_ME;
result.central = MEt2_(
ev.central().mur,
ev.incoming(), ev.outgoing(),
true
);
known_ME.emplace(ev.central().mur, result.central);
result.variations.reserve(ev.variations().size());
for(auto const & param: ev.variations()){
const double mur = param.mur;
auto cur_ME = known_ME.find(mur);
if(cur_ME == known_ME.end()){
const double ME = MEt2_.tree_param(
mur, ev.incoming(), ev.outgoing()
)*ME_kin*MEt2_.virtual_corrections(
mur, ev.incoming(), ev.outgoing()
);
cur_ME = known_ME.emplace(mur, ME).first;
}
result.variations.emplace_back(cur_ME->second);
}
assert(result.variations.size() == ev.variations().size());
return result;
}
double EventReweighter::tree_matrix_element(Event const & ev) const{
assert(ev.variations().empty());
assert(treat_.count(ev.type()) > 0);
if(treat_.find(ev.type())->second == EventTreatment::keep){
return fixed_order_scale_ME(ev).central;
}
return MEt2_.tree(
ev.central().mur,
ev.incoming(), ev.outgoing(),
false
);
}
EventReweighter::EventFactors
EventReweighter::fixed_order_scale_ME(Event const & ev) const{
const int alpha_s_power = std::count_if(
begin(ev.outgoing()), end(ev.outgoing()),
[](Sparticle const & p){ return is_parton(p); }
);
EventFactors result;
result.central = pow(pdf_.Halphas(ev.central().mur), alpha_s_power);
for(auto const & var: ev.variations()){
result.variations.emplace_back(
pow(pdf_.Halphas(var.mur), alpha_s_power)
);
}
return result;
}
}

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