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diff --git a/FixedOrderGen/src/PhaseSpacePoint.cc b/FixedOrderGen/src/PhaseSpacePoint.cc
index 6080e6b..f922cd4 100644
--- a/FixedOrderGen/src/PhaseSpacePoint.cc
+++ b/FixedOrderGen/src/PhaseSpacePoint.cc
@@ -1,420 +1,419 @@
#include "PhaseSpacePoint.hh"
#include <random>
#include "RHEJ/kinematics.hh"
#include "RHEJ/utility.hh"
-#include "RHEJ/debug.hh"
#include "RHEJ/exceptions.hh"
#include "Process.hh"
#include <CLHEP/Random/Randomize.h>
#include <CLHEP/Random/RanluxEngine.h>
using namespace RHEJ;
namespace HEJFOG{
static_assert(
std::numeric_limits<double>::has_quiet_NaN,
"no quiet NaN for double"
);
constexpr double NaN = std::numeric_limits<double>::quiet_NaN();
RHEJ::UnclusteredEvent to_UnclusteredEvent(PhaseSpacePoint const & psp){
RHEJ::UnclusteredEvent result;
result.incoming = psp.incoming();
std::sort(
begin(result.incoming), end(result.incoming),
[](Particle o1, Particle 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),
RHEJ::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;
}
namespace{
bool can_swap_to_uno(
RHEJ::Particle const & p1, RHEJ::Particle const & p2
){
return is_parton(p1)
&& p1.type != RHEJ::pid::gluon
&& p2.type == RHEJ::pid::gluon;
}
}
void PhaseSpacePoint::maybe_turn_to_uno(
double chance,
RHEJ::RNG & ran
){
assert(outgoing_.size() >= 2);
const size_t nout = outgoing_.size();
const bool can_be_uno_backward = can_swap_to_uno(
outgoing_[0], outgoing_[1]
);
const bool can_be_uno_forward = can_swap_to_uno(
outgoing_[nout-1], outgoing_[nout-2]
);
if(!can_be_uno_backward && !can_be_uno_forward) return;
if(ran.flat() < chance){
weight_ /= chance;
if(can_be_uno_backward && can_be_uno_forward){
if(ran.flat() < 0.5){
std::swap(outgoing_[0].type, outgoing_[1].type);
}
else{
std::swap(outgoing_[nout-1].type, outgoing_[nout-2].type);
}
weight_ *= 2.;
}
else if(can_be_uno_backward){
std::swap(outgoing_[0].type, outgoing_[1].type);
}
else{
assert(can_be_uno_forward);
std::swap(outgoing_[nout-1].type, outgoing_[nout-2].type);
}
}
else weight_ /= 1 - chance;
}
PhaseSpacePoint::PhaseSpacePoint(
Process const & proc,
fastjet::JetDefinition jet_def,double jetptmin, double rapmax,
RHEJ::PDF & pdf, double E_beam,
double uno_chance,
HiggsProperties const & h,
RHEJ::RNG & ran
):
jetptmin_{jetptmin},
jet_def_{jet_def}
{
assert(proc.njets >= 2);
const int nout = proc.njets + (proc.boson?1:0);
status_ = good;
weight_ = 1;
weight_ /= std::tgamma(nout);
outgoing_.reserve(nout);
for(auto&& p_out: gen_LO_partons(proc.njets, jetptmin_, E_beam, rapmax, ran)){
outgoing_.emplace_back(Particle{pid::gluon, std::move(p_out)});
}
if(status_ != good) return;
if(proc.boson && *proc.boson == pid::Higgs){
// The Higgs
auto Hparticle=gen_boson(pid::higgs, h.mass, h.width, ran);
auto pos=std::upper_bound(
begin(outgoing_),end(outgoing_),Hparticle,rapidity_less{}
);
outgoing_.insert(pos, Hparticle);
if(! h.decays.empty()){
const int boson_idx = std::distance(begin(outgoing_), pos);
decays_.emplace(
boson_idx,
decay_boson(outgoing_[boson_idx], h.decays, ran)
);
}
}
reconstruct_incoming(proc.incoming, pdf, E_beam, ran);
if(status_ != good) return;
// set outgoing states
most_backward_FKL(outgoing_).type = incoming_[0].type;
most_forward_FKL(outgoing_).type = incoming_[1].type;
if(proc.njets > 2) maybe_turn_to_uno(uno_chance, ran);
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_LO_partons(
int np , double ptmin, double ptmax, double rapmax,
RHEJ::RNG & ran
){
if (np<2) throw std::invalid_argument{"Not enough partons in gen_LO_partons"};
// heuristic parameters for pt sampling
const double ptpar = ptmin + np/5.;
const double arg_small_y = atan((ptmax - ptmin)/ptpar);
const double y_cut = 3.;
weight_ /= pow(16.*pow(M_PI,3),np-2);
std::vector<fastjet::PseudoJet> partons;
partons.reserve(np);
for(int i = 0; i < np; ++i){
const double y = -rapmax + 2*rapmax*ran.flat();
weight_ *= 2*rapmax;
const double phi = 2*M_PI*ran.flat();
weight_ *= 2.0*M_PI;
double pt;
const double r1 = ran.flat();
if(y < y_cut){
pt = ptmin + ptpar*tan(r1*arg_small_y);
const double temp = cos(r1*arg_small_y);
weight_ *= pt*ptpar*arg_small_y/(temp*temp);
}
else{
const double ptpar2 = ptpar/(1 + 5*(y-y_cut));
const double temp = 1. - std::exp((ptmin-ptmax)/ptpar2);
pt = ptmin - ptpar2*std::log(1-r1*temp);
weight_ *= pt*ptpar2*temp/(1-r1*temp);
}
partons.emplace_back(fastjet::PtYPhiM(pt, y, phi));
assert(ptmin-1e-5 <= partons[i].pt() && partons[i].pt() <= ptmax+1e-5);
}
// Need to check that at LO, the number of jets = number of partons;
fastjet::ClusterSequence cs(partons, jet_def_);
auto cluster_jets=cs.inclusive_jets(jetptmin_);
if (cluster_jets.size()!=unsigned(np)){
weight_=0.0;
status_ = not_enough_jets;
return {};
}
std::sort(begin(partons), end(partons), rapidity_less{});
return partons;
}
Particle PhaseSpacePoint::gen_boson(
RHEJ::ParticleID bosonid, double mass, double width,
RHEJ::RNG & ran
){
std::array<double,2> ptrans{0.,0.};
for (auto const & parton:outgoing_) {
ptrans[0]-=parton.px();
ptrans[1]-=parton.py();
}
// The Higgs:
// Generate a y Gaussian distributed around 0
const double y = random_normal(1.6, ran);
const double r1 = ran.flat();
const double sH = mass*(
mass + width*tan(M_PI/2.*r1 + (r1-1.)*atan(mass/width))
);
const double mHperp=sqrt(ptrans[0]*ptrans[0]+ptrans[1]*ptrans[1]+sH);
const double pz=mHperp*sinh(y);
const double E=mHperp*cosh(y);
return Particle{bosonid,fastjet::PseudoJet{ptrans[0],ptrans[1],pz,E}};
}
Particle const & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> const & partons
) const{
if(!RHEJ::is_parton(partons[0])) return partons[1];
return partons[0];
}
Particle const & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> const & partons
) const{
const size_t last_idx = partons.size() - 1;
if(!RHEJ::is_parton(partons[last_idx])) return partons[last_idx-1];
return partons[last_idx];
}
Particle & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> & partons
) const{
if(!RHEJ::is_parton(partons[0])) return partons[1];
return partons[0];
}
Particle & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> & partons
) const{
const size_t last_idx = partons.size() - 1;
if(!RHEJ::is_parton(partons[last_idx])) return partons[last_idx-1];
return partons[last_idx];
}
void PhaseSpacePoint::reconstruct_incoming(
std::array<RHEJ::ParticleID, 2> const & ids,
RHEJ::PDF & pdf, double E_beam,
RHEJ::RNG & ran
){
std::tie(incoming_[0].p, incoming_[1].p) = incoming_momenta(outgoing_);
// calculate xa, xb
const double sqrts=2*E_beam;
const double xa=(incoming_[0].p.e()-incoming_[0].p.pz())/sqrts;
const double xb=(incoming_[1].p.e()+incoming_[1].p.pz())/sqrts;
// abort if phase space point is outside of collider energy reach
if (xa>1. || xb>1.){
weight_=0;
status_ = too_much_energy;
return;
}
// pick pdfs
/** TODO:
* ufa, ufb don't correspond to our final scale choice.
* The reversed HEJ scale generators currently expect a full event as input,
* so fixing this is not completely trivial
*/
if(ids[0] == pid::proton || ids[0] == pid::p_bar){
const double ufa=jetptmin_;
incoming_[0].type = generate_incoming_id(xa, ufa, pdf, ran);
}
else {
incoming_[0].type = ids[0];
}
if(ids[1] == pid::proton || ids[1] == pid::p_bar){
const double ufb=jetptmin_;
incoming_[1].type = generate_incoming_id(xb, ufb, pdf, ran);
}
else {
incoming_[1].type = ids[1];
}
assert(momentum_conserved(1e-7));
}
RHEJ::ParticleID PhaseSpacePoint::generate_incoming_id(
double x, double uf, RHEJ::PDF & pdf,
RHEJ::RNG & ran
){
const double pdfg=fabs(pdf.pdfpt(0,x,uf,pid::gluon));
const double pdfu=fabs(pdf.pdfpt(0,x,uf,pid::up));
const double pdfd=fabs(pdf.pdfpt(0,x,uf,pid::down));
const double pdfux=fabs(pdf.pdfpt(0,x,uf,pid::u_bar));
const double pdfdx=fabs(pdf.pdfpt(0,x,uf,pid::d_bar));
const double pdfc=fabs(pdf.pdfpt(0,x,uf,pid::charm));
const double pdfs=fabs(pdf.pdfpt(0,x,uf,pid::strange));
const double pdfsx=fabs(pdf.pdfpt(0,x,uf,pid::s_bar));
const double pdfb=fabs(pdf.pdfpt(0,x,uf,pid::b));
const double pdftot=pdfg+4.0/9.0*(pdfu + pdfd + pdfux + pdfdx +pdfs +pdfsx + 2.0*(pdfc +pdfb ));
const double r1=pdftot*ran.flat();
double sum;
if (r1<(sum=pdfg)) {
weight_*=pdftot/pdfg;
return pid::gluon;
}
if (r1<(sum+=(4./9.)*pdfu)) {
weight_*=pdftot/((4./9.)*pdfu);
return pid::up;
}
else if (r1<(sum+=(4./9.)*pdfd)) {
weight_*=pdftot/((4./9.)*pdfd);
return pid::down;
}
else if (r1<(sum+=(4./9.)*pdfux)) {
weight_*=pdftot/((4./9.)*pdfux);
return pid::u_bar;
}
else if (r1<(sum+=(4./9.)*pdfdx)) {
weight_*=pdftot/((4./9.)*pdfdx);
return pid::d_bar;
}
else if (r1<(sum+=(4./9.)*pdfc)) {
weight_*=pdftot/((4./9.)*pdfc);
return pid::c;
}
else if (r1<(sum+=(4./9.)*pdfc)){
weight_*=pdftot/((4./9.)*pdfc);
return pid::c_bar;
}
else if (r1<(sum+=(4./9.)*pdfs)) {
weight_*=pdftot/((4./9.)*pdfs);
return pid::s;
}
else if (r1<(sum+=(4./9.)*pdfsx)) {
weight_*=pdftot/((4./9.)*pdfsx);
return pid::s_bar;
}
else if (r1<(sum+=(4./9.)*pdfb)) {
weight_*=pdftot/((4./9.)*pdfb);
return pid::b;
}
else if (r1<=(sum+=(4./9.)*pdfb)) {
weight_*=pdftot/((4./9.)*pdfb);
return pid::b_bar;
}
std::cout << "Error in choosing incoming parton: "<<x<<" "<<uf<<" "<<sum<<" "<<pdftot<<" "<<r1;
std::cout << " "<<pdfg+4./9.*(pdfu+pdfux+pdfd+pdfdx+pdfs+pdfsx+2.*(pdfc+pdfb))<<std::endl;
throw std::logic_error{"Failed to choose parton flavour"};
}
double PhaseSpacePoint::random_normal(
double stddev,
RHEJ::RNG & ran
){
const double r1 = ran.flat();
const double r2 = ran.flat();
const double lninvr1 = -log(r1);
const double result = stddev*sqrt(2.*lninvr1)*cos(2.*M_PI*r2);
weight_ *= exp(result*result/(2*stddev*stddev))*sqrt(2.*M_PI)*stddev;
return result;
}
bool PhaseSpacePoint::momentum_conserved(double ep) const{
fastjet::PseudoJet diff;
for(auto const & in: incoming()) diff += in.p;
for(auto const & out: outgoing()) diff -= out.p;
return nearby_ep(diff, fastjet::PseudoJet{}, ep);
}
Decay PhaseSpacePoint::select_decay_channel(
std::vector<Decay> const & decays,
RHEJ::RNG & ran
){
double br_total = 0.;
for(auto const & decay: decays) br_total += decay.branching_ratio;
// adjust weight
// this is given by (channel branching ratio)/(chance to pick channel)
// where (chance to pick channel) =
// (channel branching ratio)/(total branching ratio)
weight_ *= br_total;
const double r1 = br_total*ran.flat();
double br_sum = 0.;
for(auto const & decay: decays){
br_sum += decay.branching_ratio;
if(r1 < br_sum) return decay;
}
throw std::logic_error{"unreachable"};
}
std::vector<Particle> PhaseSpacePoint::decay_boson(
RHEJ::Particle const & parent,
std::vector<Decay> const & decays,
RHEJ::RNG & ran
){
const auto channel = select_decay_channel(decays, ran);
if(channel.products.size() != 2){
throw RHEJ::not_implemented{
"only decays into two particles are implemented"
};
}
std::vector<Particle> decay_products(channel.products.size());
for(size_t i = 0; i < channel.products.size(); ++i){
decay_products[i].type = channel.products[i];
}
// choose polar and azimuth angle in parent rest frame
const double E = parent.m()/2;
const double theta = 2.*M_PI*ran.flat();
const double cos_phi = 2.*ran.flat()-1.;
const double sin_phi = sqrt(1. - cos_phi*cos_phi); // Know 0 < phi < pi
const double px = E*cos(theta)*sin_phi;
const double py = E*sin(theta)*sin_phi;
const double pz = E*cos_phi;
decay_products[0].p.reset(px, py, pz, E);
decay_products[1].p.reset(-px, -py, -pz, E);
for(auto & particle: decay_products) particle.p.boost(parent.p);
return decay_products;
}
}
diff --git a/FixedOrderGen/t/h_2j_decay.cc b/FixedOrderGen/t/h_2j_decay.cc
index 688c1e4..a269595 100644
--- a/FixedOrderGen/t/h_2j_decay.cc
+++ b/FixedOrderGen/t/h_2j_decay.cc
@@ -1,82 +1,82 @@
#ifdef NDEBUG
#undef NDEBUG
#endif
#include <algorithm>
#include <cmath>
#include <cassert>
#include <iostream>
#include "config.hh"
#include "EventGenerator.hh"
#include "RHEJ/Ranlux64.hh"
#include "RHEJ/PDF.hh"
#include "RHEJ/MatrixElement.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.hh"
using namespace HEJFOG;
bool pass_dR_cut(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<RHEJ::Particle> const & photons
){
constexpr double delta_R_min = 0.7;
for(auto const & jet: jets){
for(auto const & photon: photons){
if(jet.delta_R(photon.p) < delta_R_min) return false;
}
}
return true;
}
int main(){
constexpr double invGeV2_to_pb = 389379292.;
constexpr double xs_ref = 0.00425287; //calculated with "old" HEJ svn r3364
auto config = load_config("config_h_2j_decay.yml");
RHEJ::Ranlux64 ran{};
HEJFOG::EventGenerator generator{
config.process,
config.beam,
RHEJ::ScaleGenerator{
config.scales.base,
config.scales.factors,
config.scales.max_ratio
},
config.jets,
config.pdf_id,
config.unordered_fraction,
config.Higgs_properties,
config.Higgs_coupling,
ran
};
double xs = 0., xs_err = 0.;
for (int trials = 0; trials < config.events; ++trials){
auto ev = generator.gen_event();
if(generator.status() != good) continue;
assert(ev.decays().size() == 1);
const auto decay = begin(ev.decays());
assert(ev.outgoing().size() > static_cast<size_t>(decay->first));
const auto & the_Higgs = ev.outgoing()[decay->first];
assert(the_Higgs.type == RHEJ::pid::Higgs);
assert(decay->second.size() == 2);
auto const & gamma = decay->second;
assert(gamma[0].type == RHEJ::pid::photon);
assert(gamma[1].type == RHEJ::pid::photon);
- assert(nearby_ep(gamma[0].p + gamma[1].p, the_Higgs.p, 1e-6));
+ assert(RHEJ::nearby_ep(gamma[0].p + gamma[1].p, the_Higgs.p, 1e-6));
if(!pass_dR_cut(ev.jets(), gamma)) continue;
ev.central().weight *= invGeV2_to_pb;
ev.central().weight /= config.events;
xs += ev.central().weight;
xs_err += ev.central().weight*ev.central().weight;
}
xs_err = std::sqrt(xs_err);
std::cout << xs_ref << " ~ " << xs << " +- " << xs_err << '\n';
assert(std::abs(xs - xs_ref) < 3*xs_err);
assert(xs_err < 0.012*xs);
}
diff --git a/include/RHEJ/debug.hh b/include/RHEJ/debug.hh
deleted file mode 100644
index 7432727..0000000
--- a/include/RHEJ/debug.hh
+++ /dev/null
@@ -1,58 +0,0 @@
-#pragma once
-
-#include <iostream>
-#include <cassert>
-
-#include "fastjet/PseudoJet.hh"
-
-inline
-std::ostream & operator<<(std::ostream & o, fastjet::PseudoJet const & p){
- o << '(';
- for(size_t i = 0; i < 3; ++i) o << p[i] << ", ";
- return o << p[3] << ')';
-}
-
-// to work around compiler warnings for unused variables
-template<typename... T>
-void ignore(T&&...) {}
-
-inline
-void dprint() {};
-
-template<typename T, typename... Rest>
-void dprint(T&& t, Rest&&... r){
- ignore(std::forward<T>(t), std::forward<Rest>(r)...);
- #ifndef NDEBUG
- std::cout << std::forward<T>(t);
- dprint(std::forward<Rest>(r)...);
- #endif
-}
-
-//check whether two doubles are closer than ep > 0 to each other
-inline
-bool nearby_ep(double a, double b, double ep){
- ignore(a, b, ep);
- assert(ep > 0);
- return std::abs(a-b) < ep;
-}
-
-//check whether two four-vectors are close to each other
-inline
-bool nearby_ep(
- fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb,
- double ep
-){
- ignore(pa, pb, ep);
- assert(ep > 0);
- for(size_t i = 0; i < 4; ++i){
- if(!nearby_ep(pa[i], pb[i], ep)) return false;
- }
- return true;
-}
-
-inline
-bool nearby(
- fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb, double const norm = 1.
-){
- return nearby_ep(pa, pb, 1e-7*norm);
-}
diff --git a/include/RHEJ/utility.hh b/include/RHEJ/utility.hh
index 41e1dc6..c6ad7b4 100644
--- a/include/RHEJ/utility.hh
+++ b/include/RHEJ/utility.hh
@@ -1,166 +1,198 @@
/**
* \file
* \brief Contains various utilities
*/
#pragma once
#include <algorithm>
+#include <cassert>
#include <boost/core/demangle.hpp>
// FastJet Includes
#include "fastjet/PseudoJet.hh"
#include "fastjet/ClusterSequence.hh"
#include "RHEJ/PDG_codes.hh"
namespace RHEJ{
//! Class representing a particle
struct Particle {
//! particle type
ParticleID type;
//! particle momentum
fastjet::PseudoJet p;
//! get rapidity
double rapidity() const{
return p.rapidity();
}
//! get transverse momentum
double perp() const{
return p.perp();
}
//! get momentum in x direction
double px() const{
return p.px();
}
//! get momentum in y direction
double py() const{
return p.py();
}
//! get momentum in z direction
double pz() const{
return p.pz();
}
//! get energy
double E() const{
return p.E();
}
//! get mass
double m() const{
return p.m();
}
};
//! Functor to compare rapidities
/**
* This can be used whenever a rapidity comparison function is needed,
* for example in many standard library functions.
*
* @see pz_less
*/
struct rapidity_less{
template<class FourVector>
bool operator()(FourVector const & p1, FourVector const & p2){
return p1.rapidity() < p2.rapidity();
}
};
//! Functor to compare momenta in z direction
/**
* This can be used whenever a pz comparison function is needed,
* for example in many standard library functions.
*
* @see rapidity_less
*/
struct pz_less{
template<class FourVector>
bool operator()(FourVector const & p1, FourVector const & p2){
return p1.pz() < p2.pz();
}
};
//! Convert a vector of Particles to a vector of particle momenta
inline
std::vector<fastjet::PseudoJet> to_PseudoJet(
std::vector<Particle> const & v
){
std::vector<fastjet::PseudoJet> result;
for(auto && sp: v) result.emplace_back(sp.p);
return result;
}
//! Check if a particle is a parton, i.e. quark, antiquark, or gluon
inline
bool is_parton(Particle const & p){
return is_parton(p.type);
}
//! Check if a particle is a photon, W, Z, or Higgs boson
inline bool is_AWZH_boson(Particle const & particle){
return is_AWZH_boson(particle.type);
}
//! Extract all partons from a vector of particles
inline
std::vector<Particle> filter_partons(
std::vector<Particle> const & v
){
std::vector<Particle> result;
result.reserve(v.size());
std::copy_if(
begin(v), end(v), std::back_inserter(result),
[](Particle const & p){ return is_parton(p); }
);
return result;
}
//! Create a std::unique_ptr to a T object
/**
* For non-array types this works like std::make_unique,
* which is not available under C++11
*/
template<class T, class... Args>
std::unique_ptr<T> make_unique(Args&&... a){
return std::unique_ptr<T>{new T{std::forward<Args>(a)...}};
}
//! Create an array containing the passed arguments
template<typename T, typename... U>
constexpr
std::array<T, 1 + sizeof...(U)> make_array(T t, U&&... rest){
return {{t, std::forward<U>(rest)...}};
}
inline
std::string join(
std::string const & /* delim */, std::string const & str
){
return str;
}
//! Join strings with a delimiter
/**
* @param delim Delimiter to be put between consecutive strings
* @param first First string
* @param second Second string
* @param rest Remaining strings
*/
template<typename... Strings>
std::string join(
std::string const & delim,
std::string const & first, std::string const & second,
Strings&&... rest
){
return join(delim, first + delim + second, std::forward<Strings>(rest)...);
}
//! Return the name of the argument's type
template<typename T>
std::string type_string(T&&){
return boost::core::demangle(typeid(T).name());
}
+ //! Eliminate compiler warnings for unused variables
+ template<typename... T>
+ constexpr void ignore(T&&...) {}
+
+ //! Check whether two doubles are closer than ep > 0 to each other
+ inline
+ bool nearby_ep(double a, double b, double ep){
+ assert(ep > 0);
+ return std::abs(a-b) < ep;
+ }
+
+ //! Check whether all components of two PseudoJets are closer than ep to each other
+ inline
+ bool nearby_ep(
+ fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb,
+ double ep
+ ){
+ assert(ep > 0);
+ for(size_t i = 0; i < 4; ++i){
+ if(!nearby_ep(pa[i], pb[i], ep)) return false;
+ }
+ return true;
+ }
+
+ inline
+ bool nearby(
+ fastjet::PseudoJet const & pa, fastjet::PseudoJet const & pb, double const norm = 1.
+ ){
+ return nearby_ep(pa, pb, 1e-7*norm);
+ }
+
}
diff --git a/src/Event.cc b/src/Event.cc
index 0995f25..f2aaad2 100644
--- a/src/Event.cc
+++ b/src/Event.cc
@@ -1,343 +1,343 @@
#include "RHEJ/Event.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.hh"
namespace RHEJ{
namespace{
constexpr int status_in = -1;
constexpr int status_decayed = 2;
constexpr int status_out = 1;
// helper functions to determine event type
// 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(std::vector<Particle> const & outgoing){
bool has_AWZH_boson = false;
for(auto const & out: outgoing){
if(is_AWZH_boson(out.type)){
if(has_AWZH_boson) return false;
has_AWZH_boson = true;
}
else if(! is_parton(out.type)) return false;
}
return true;
}
template<class Iterator>
Iterator remove_AWZH(Iterator begin, Iterator end){
return std::remove_if(
begin, end, [](Particle const & p){return is_AWZH_boson(p);}
);
}
template<class Iterator>
bool valid_outgoing(Iterator begin, Iterator end){
return std::distance(begin, end) >= 2
&& std::is_sorted(begin, end, rapidity_less{})
&& std::count_if(
begin, end, [](Particle const & s){return is_AWZH_boson(s);}
) < 2;
}
// Note that this changes the outgoing range!
template<class ConstIterator, class Iterator>
bool is_FKL(
ConstIterator begin_incoming, ConstIterator end_incoming,
Iterator begin_outgoing, Iterator end_outgoing
){
assert(std::distance(begin_incoming, end_incoming) == 2);
assert(std::distance(begin_outgoing, end_outgoing) >= 2);
// One photon, W, H, Z in the final state is allowed.
// Remove it for remaining tests,
end_outgoing = remove_AWZH(begin_outgoing, end_outgoing);
// Test if this is a standard FKL configuration.
return
(begin_incoming->type == begin_outgoing->type)
&& ((end_incoming-1)->type == (end_outgoing-1)->type)
&& std::all_of(
begin_outgoing + 1, end_outgoing - 1,
[](Particle const & p){ return p.type == pid::gluon; }
);
}
bool is_FKL(
std::array<Particle, 2> const & incoming,
std::vector<Particle> outgoing
){
assert(std::is_sorted(begin(incoming), end(incoming), pz_less{}));
assert(valid_outgoing(begin(outgoing), end(outgoing)));
return is_FKL(
begin(incoming), end(incoming),
begin(outgoing), end(outgoing)
);
}
bool has_2_jets(Event const & event){
return event.jets().size() >= 2;
}
/**
* \brief Checks whether event is unordered backwards
* @param ev Event
* @returns Is Event Unordered Backwards
*
* Checks there is more than 3 constuents in the final state
* Checks there is more than 3 jets
* Checks the most backwards parton is a gluon
* Checks the most forwards jet is not a gluon
* Checks the rest of the event is FKL
* Checks the second most backwards is not a different boson
* Checks the unordered gluon actually forms a jet
*/
bool is_unordered_backward(Event const & ev){
auto const & in = ev.incoming();
auto const & out = ev.outgoing();
assert(std::is_sorted(begin(in), end(in), pz_less{}));
assert(valid_outgoing(begin(out), end(out)));
if(out.size() < 3) return false;
if(ev.jets().size() < 3) return false;
if(in.front().type == pid::gluon) return false;
if(out.front().type != pid::gluon) return false;
// When skipping the unordered emission
// the remainder should be a regular FKL event,
// except that the (new) first outgoing particle must not be a A,W,Z,H.
const auto FKL_begin = next(begin(out));
if(is_AWZH_boson(*FKL_begin)) return false;
if(!is_FKL(in, {FKL_begin, end(out)})) return false;
// check that the unordered gluon forms an extra jet
const auto jets = sorted_by_rapidity(ev.jets());
const auto indices = ev.particle_jet_indices({jets.front()});
return indices[0] >= 0 && indices[1] == -1;
}
/**
* \brief Checks for a forward unordered gluon emission
* @param ev Event
* @returns Is the event a forward unordered emission
*
* \see is_unordered_backward
*/
bool is_unordered_forward(Event const & ev){
auto const & in = ev.incoming();
auto const & out = ev.outgoing();
assert(std::is_sorted(begin(in), end(in), pz_less{}));
assert(valid_outgoing(begin(out), end(out)));
if(out.size() < 3) return false;
if(ev.jets().size() < 3) return false;
if(in.back().type == pid::gluon) return false;
if(out.back().type != pid::gluon) return false;
// When skipping the unordered emission
// the remainder should be a regular FKL event,
// except that the (new) last outgoing particle must not be a A,W,Z,H.
const auto FKL_end = prev(end(out));
if(is_AWZH_boson(*prev(FKL_end))) return false;
if(!is_FKL(in, {begin(out), FKL_end})) return false;
// check that the unordered gluon forms an extra jet
const auto jets = sorted_by_rapidity(ev.jets());
const auto indices = ev.particle_jet_indices({jets.back()});
return indices.back() >= 0 && indices[indices.size()-2] == -1;
}
using event_type::EventType;
EventType classify(Event const & ev){
if(! final_state_ok(ev.outgoing())) return EventType::bad_final_state;
if(! has_2_jets(ev)) return EventType::no_2_jets;
if(is_FKL(ev.incoming(), ev.outgoing())) return EventType::FKL;
if(is_unordered_backward(ev)){
return EventType::unordered_backward;
}
if(is_unordered_forward(ev)){
return EventType::unordered_forward;
}
return EventType::nonHEJ;
}
Particle extract_particle(LHEF::HEPEUP const & hepeup, int i){
return Particle{
static_cast<ParticleID>(hepeup.IDUP[i]),
fastjet::PseudoJet{
hepeup.PUP[i][0], hepeup.PUP[i][1],
hepeup.PUP[i][2], hepeup.PUP[i][3]
}
};
}
bool is_decay_product(std::pair<int, int> const & mothers){
if(mothers.first == 0) return false;
return mothers.second == 0 || mothers.first == mothers.second;
}
}
UnclusteredEvent::UnclusteredEvent(LHEF::HEPEUP const & hepeup):
central(EventParameters{
hepeup.scales.mur, hepeup.scales.muf, hepeup.weight()
})
{
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] == 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));
}
std::sort(
begin(incoming), end(incoming),
[](Particle o1, Particle o2){return o1.p.pz()<o2.p.pz();}
);
std::sort(begin(outgoing), end(outgoing), rapidity_less{});
// 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 ev,
fastjet::JetDefinition const & jet_def, double min_jet_pt
):
ev_{std::move(ev)},
cs_{to_PseudoJet(filter_partons(ev_.outgoing)), jet_def},
min_jet_pt_{min_jet_pt}
{
type_ = classify(*this);
}
std::vector<fastjet::PseudoJet> Event::jets() const{
return cs_.inclusive_jets(min_jet_pt_);
}
/**
* \brief Returns the invarient mass of the event
* @param ev Event
* @returns s hat
*
* Makes use of the FastJet PseudoJet function m2().
* Applies this function to the sum of the incoming partons.
*/
double shat(Event const & ev){
return (ev.incoming()[0].p + ev.incoming()[1].p).m2();
}
namespace{
// colour flow according to Les Houches standard
// TODO: stub
std::vector<std::pair<int, int>> colour_flow(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing
){
std::vector<std::pair<int, int>> result(
incoming.size() + outgoing.size()
);
for(auto & col: result){
col = std::make_pair(-1, -1);
}
return result;
}
}
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()+1; // event ID
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;
for(Particle const & in: event.incoming()){
result.IDUP.emplace_back(in.type);
result.ISTUP.emplace_back(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);
}
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)?status_decayed: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);
}
result.ICOLUP = colour_flow(
event.incoming(), filter_partons(event.outgoing())
);
if(result.ICOLUP.size() < num_particles){
const size_t AWZH_boson_idx = std::find_if(
begin(event.outgoing()), end(event.outgoing()),
[](Particle const & s){ return is_AWZH_boson(s); }
) - begin(event.outgoing()) + event.incoming().size();
assert(AWZH_boson_idx <= result.ICOLUP.size());
result.ICOLUP.insert(
begin(result.ICOLUP) + AWZH_boson_idx,
std::make_pair(0,0)
);
}
for(auto const & decay: event.decays()){
for(auto const out: decay.second){
result.IDUP.emplace_back(out.type);
result.ISTUP.emplace_back(status_out);
result.PUP.push_back({out.p[0], out.p[1], out.p[2], out.p[3], out.p.m()});
const int 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;
}
}
diff --git a/src/EventReweighter.cc b/src/EventReweighter.cc
index f89ac3c..ca61aa6 100644
--- a/src/EventReweighter.cc
+++ b/src/EventReweighter.cc
@@ -1,326 +1,326 @@
#include "RHEJ/EventReweighter.hh"
#include <string>
#include <unordered_map>
#include "RHEJ/PhaseSpacePoint.hh"
#include "RHEJ/PDG_codes.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.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),
[](Particle o1, Particle 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;
}
} // namespace anonymous
EventReweighter::EventReweighter(
LHEF::HEPRUP const & heprup,
ScaleGenerator scale_gen,
EventReweighterConfig conf,
RHEJ::RNG & ran
):
EventReweighter{
RHEJ::Beam{
heprup.EBMUP.first,
{{
static_cast<RHEJ::ParticleID>(heprup.IDBMUP.first),
static_cast<RHEJ::ParticleID>(heprup.IDBMUP.second)
}}
},
heprup.PDFSUP.first,
std::move(scale_gen),
std::move(conf),
ran
}
{
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,
ScaleGenerator scale_gen,
EventReweighterConfig conf,
RHEJ::RNG & ran
):
param_{std::move(conf)},
E_beam_{beam.E},
pdf_{pdf_id, beam.type.front(), beam.type.back()},
MEt2_{
[this](double mu){ return pdf_.Halphas(mu); },
param_.ME_config
},
scale_gen_(std::move(scale_gen)),
ran_{ran}
{}
PDF const & EventReweighter::pdf() const{
return pdf_;
}
std::vector<Event> EventReweighter::reweight(
Event const & input_ev, int num_events
){
auto res_events = gen_res_events(input_ev, num_events);
if(res_events.empty()) return {};
for(auto & event: res_events) event = scale_gen_(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(param_.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, param_.psp_config, ran_};
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)),
param_.jet_param.def, param_.jet_param.min_pt
);
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;
};
/**
* \brief Do the Jets pass the resummation Cuts?
*
* @param ev Event in Question
* @returns 0 or 1 depending on if ev passes Jet Cuts
*/
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, param_.jet_param.def};
return cs.inclusive_jets(param_.jet_param.min_pt).size() == ev.jets().size();
}
/**
* \brief pdf_factors Function
*
* @param ev Event in Question
* @returns EventFactor due to PDFs
*
* Calculates the Central value and the variation due
* to the PDF choice made.
*/
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 & ev_param: ev.variations()){
const double muf = ev_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;
}
/**
* \brief matrix_elements Function
*
* @param ev Event in question
* @returns EventFactor due to MatrixElements
*
* Calculates the Central value and the variation due
* to the Matrix Element.
*/
EventReweighter::EventFactors
EventReweighter::matrix_elements(Event const & ev) const{
assert(param_.treat.count(ev.type()) > 0);
if(param_.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;
}
/**
* \brief Computes the tree level matrix element
*
* @param ev Event in Question
* @returns HEJ approximation to Tree level Matrix Element
*
* This computes the HEJ approximation to the tree level FO
* Matrix element which is used within the LO weighting process.
*/
double EventReweighter::tree_matrix_element(Event const & ev) const{
assert(ev.variations().empty());
assert(param_.treat.count(ev.type()) > 0);
if(param_.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
);
}
/**
* \brief Scale-dependent part of fixed-order matrix element
*
* @param ev Event in question
* @returns EventFactor scale variation due to FO-ME.
*
* This is only called to compute the scale variation for events where
* we don't do resummation (e.g. non-FKL).
* Since at tree level the scale dependence is just due to alpha_s,
* it is enough to return the alpha_s(mur) factors in the matrix element.
* The rest drops out in the ratio of (output event ME)/(input event ME),
* so we never have to compute it.
*/
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()),
[](Particle 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;
}
}
diff --git a/src/MatrixElement.cc b/src/MatrixElement.cc
index a67bbc3..637a262 100644
--- a/src/MatrixElement.cc
+++ b/src/MatrixElement.cc
@@ -1,761 +1,761 @@
#include "RHEJ/MatrixElement.hh"
#include <CLHEP/Random/Randomize.h>
#include <CLHEP/Random/RanluxEngine.h>
#include "RHEJ/Constants.hh"
#include "RHEJ/currents.hh"
#include "RHEJ/PDG_codes.hh"
#include "RHEJ/uno.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.hh"
namespace RHEJ{
//cf. last line of eq. (22) in \ref Andersen:2011hs
double MatrixElement::omega0(
double alpha_s, double mur,
fastjet::PseudoJet const & q_j, double lambda
) const {
const double result = - alpha_s*N_C/M_PI*log(q_j.perp2()/(lambda*lambda));
if(! param_.log_correction) return result;
// use alpha_s(sqrt(q_j*lambda)), evolved to mur
return (
1. + alpha_s/(4.*M_PI)*beta0*log(mur*mur/(q_j.perp()*lambda))
)*result;
}
double MatrixElement::virtual_corrections(
double mur,
std::array<Particle, 2> const & in,
std::vector<Particle> const & out
) const{
fastjet::PseudoJet const & pa = in.front().p;
#ifndef NDEBUG
fastjet::PseudoJet const & pb = in.back().p;
double const norm = (in.front().p + in.back().p).E();
#endif
assert(std::is_sorted(out.begin(), out.end(), rapidity_less{}));
assert(out.size() >= 2);
assert(pa.pz() < pb.pz());
fastjet::PseudoJet q = pa - out[0].p;
size_t first_idx = 0;
size_t last_idx = out.size() - 1;
// if there is a Higgs or unordered gluon outside the extremal partons
// then it is not part of the FKL ladder and does not contribute
// to the virtual corrections
if(out.front().type == pid::Higgs || has_unob_gluon(in, out)){
q -= out[1].p;
++first_idx;
}
if(out.back().type == pid::Higgs || has_unof_gluon(in, out)){
--last_idx;
}
double exponent = 0;
const double alpha_s = alpha_s_(mur);
for(size_t j = first_idx; j < last_idx; ++j){
exponent += omega0(alpha_s, mur, q, CLAMBDA)*(
out[j+1].rapidity() - out[j].rapidity()
);
q -= out[j+1].p;
}
assert(
nearby(q, -1*pb, norm)
|| out.back().type == pid::Higgs
|| has_unof_gluon(in, out)
);
return exp(exponent);
}
} // namespace RHEJ
namespace {
//! Lipatov vertex for partons emitted into extremal jets
double C2Lipatov(CLHEP::HepLorentzVector qav, CLHEP::HepLorentzVector qbv,
CLHEP::HepLorentzVector p1, CLHEP::HepLorentzVector p2)
{
CLHEP::HepLorentzVector temptrans=-(qav+qbv);
CLHEP::HepLorentzVector p5=qav-qbv;
CLHEP::HepLorentzVector CL=temptrans
+ p1*(qav.m2()/p5.dot(p1) + 2.*p5.dot(p2)/p1.dot(p2))
- p2*(qbv.m2()/p5.dot(p2) + 2.*p5.dot(p1)/p1.dot(p2));
// cout << "#Fadin qa : "<<qav<<endl;
// cout << "#Fadin qb : "<<qbv<<endl;
// cout << "#Fadin p1 : "<<p1<<endl;
// cout << "#Fadin p2 : "<<p2<<endl;
// cout << "#Fadin p5 : "<<p5<<endl;
// cout << "#Fadin Gauge Check : "<< CL.dot(p5)<<endl;
// cout << "#Fadin C2L : "<< -CL.dot(CL)<<" "<<-CL.dot(CL)/(qav.m2()*qbv.m2())/(4./p5.perp2())<<endl;
// TODO can this dead test go?
// if (-CL.dot(CL)<0.)
// if (fabs(CL.dot(p5))>fabs(CL.dot(CL))) // not sufficient!
// return 0.;
// else
return -CL.dot(CL);
}
//! Lipatov vertex with soft subtraction for partons emitted into extremal jets
double C2Lipatovots(CLHEP::HepLorentzVector qav, CLHEP::HepLorentzVector qbv,
CLHEP::HepLorentzVector p1, CLHEP::HepLorentzVector p2)
{
double kperp=(qav-qbv).perp();
if (kperp>RHEJ::CLAMBDA)
return C2Lipatov(qav, qbv, p1, p2)/(qav.m2()*qbv.m2());
else {
double Cls=(C2Lipatov(qav, qbv, p1, p2)/(qav.m2()*qbv.m2()));
return Cls-4./(kperp*kperp);
}
}
//! Lipatov vertex
double C2Lipatov(CLHEP::HepLorentzVector qav, CLHEP::HepLorentzVector qbv,
CLHEP::HepLorentzVector pim, CLHEP::HepLorentzVector pip,
CLHEP::HepLorentzVector pom, CLHEP::HepLorentzVector pop) // B
{
CLHEP::HepLorentzVector temptrans=-(qav+qbv);
CLHEP::HepLorentzVector p5=qav-qbv;
CLHEP::HepLorentzVector CL=temptrans
+ qav.m2()*(1./p5.dot(pip)*pip + 1./p5.dot(pop)*pop)/2.
- qbv.m2()*(1./p5.dot(pim)*pim + 1./p5.dot(pom)*pom)/2.
+ ( pip*(p5.dot(pim)/pip.dot(pim) + p5.dot(pom)/pip.dot(pom))
+ pop*(p5.dot(pim)/pop.dot(pim) + p5.dot(pom)/pop.dot(pom))
- pim*(p5.dot(pip)/pip.dot(pim) + p5.dot(pop)/pop.dot(pim))
- pom*(p5.dot(pip)/pip.dot(pom) + p5.dot(pop)/pop.dot(pom)) )/2.;
return -CL.dot(CL);
}
//! Lipatov vertex with soft subtraction
double C2Lipatovots(CLHEP::HepLorentzVector qav, CLHEP::HepLorentzVector qbv,
CLHEP::HepLorentzVector pa, CLHEP::HepLorentzVector pb,
CLHEP::HepLorentzVector p1, CLHEP::HepLorentzVector p2)
{
double kperp=(qav-qbv).perp();
if (kperp>RHEJ::CLAMBDA)
return C2Lipatov(qav, qbv, pa, pb, p1, p2)/(qav.m2()*qbv.m2());
else {
double Cls=(C2Lipatov(qav, qbv, pa, pb, p1, p2)/(qav.m2()*qbv.m2()));
double temp=Cls-4./(kperp*kperp);
return temp;
}
}
/** Matrix element squared for tree-level current-current scattering
* @param aptype Particle a PDG ID
* @param bptype Particle b PDG ID
* @param pn Particle n Momentum
* @param pb Particle b Momentum
* @param p1 Particle 1 Momentum
* @param pa Particle a Momentum
* @returns ME Squared for Tree-Level Current-Current Scattering
*/
double ME_current(
int aptype, int bptype,
CLHEP::HepLorentzVector const & pn,
CLHEP::HepLorentzVector const & pb,
CLHEP::HepLorentzVector const & p1,
CLHEP::HepLorentzVector const & pa
){
if (aptype==21&&bptype==21) {
return jM2gg(pn,pb,p1,pa);
} else if (aptype==21&&bptype!=21) {
if (bptype > 0)
return jM2qg(pn,pb,p1,pa);
else
return jM2qbarg(pn,pb,p1,pa);
}
else if (bptype==21&&aptype!=21) { // ----- || -----
if (aptype > 0)
return jM2qg(p1,pa,pn,pb);
else
return jM2qbarg(p1,pa,pn,pb);
}
else { // they are both quark
if (bptype>0) {
if (aptype>0)
return jM2qQ(pn,pb,p1,pa);
else
return jM2qQbar(pn,pb,p1,pa);
}
else {
if (aptype>0)
return jM2qQbar(p1,pa,pn,pb);
else
return jM2qbarQbar(pn,pb,p1,pa);
}
}
throw std::logic_error("unknown particle types");
}
/** \brief Matrix element squared for tree-level current-current scattering with Higgs
* @param aptype Particle a PDG ID
* @param bptype Particle b PDG ID
* @param pn Particle n Momentum
* @param pb Particle b Momentum
* @param p1 Particle 1 Momentum
* @param pa Particle a Momentum
* @param qH t-channel momentum before Higgs
* @param qHp1 t-channel momentum after Higgs
* @returns ME Squared for Tree-Level Current-Current Scattering with Higgs
*/
double ME_Higgs_current(
int aptype, int bptype,
CLHEP::HepLorentzVector const & pn,
CLHEP::HepLorentzVector const & pb,
CLHEP::HepLorentzVector const & p1,
CLHEP::HepLorentzVector const & pa,
CLHEP::HepLorentzVector const & qH, // t-channel momentum before Higgs
CLHEP::HepLorentzVector const & qHp1, // t-channel momentum after Higgs
double mt, bool include_bottom, double mb
){
if (aptype==21&&bptype==21) // gg initial state
return MH2gg(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else if (aptype==21&&bptype!=21) {
if (bptype > 0)
return MH2qg(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb)*4./9.;
else
return MH2qbarg(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb)*4./9.;
}
else if (bptype==21&&aptype!=21) {
if (aptype > 0)
return MH2qg(p1,pa,pn,pb,-qH,-qHp1,mt,include_bottom,mb)*4./9.;
else
return MH2qbarg(p1,pa,pn,pb,-qH,-qHp1,mt,include_bottom,mb)*4./9.;
}
else { // they are both quark
if (bptype>0) {
if (aptype>0)
return MH2qQ(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb)*4.*4./(9.*9.);
else
return MH2qQbar(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb)*4.*4./(9.*9.);
}
else {
if (aptype>0)
return MH2qQbar(p1,pa,pn,pb,-qH,-qHp1,mt,include_bottom,mb)*4.*4./(9.*9.);
else
return MH2qbarQbar(pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb)*4.*4./(9.*9.);
}
}
throw std::logic_error("unknown particle types");
}
/** \brief Current matrix element squared with Higgs and unordered forward emission
* @param aptype Particle A PDG ID
* @param bptype Particle B PDG ID
* @param punof Unordered Particle Momentum
* @param pn Particle n Momentum
* @param pb Particle b Momentum
* @param p1 Particle 1 Momentum
* @param pa Particle a Momentum
* @param qH t-channel momentum before Higgs
* @param qHp1 t-channel momentum after Higgs
* @returns ME Squared with Higgs and unordered forward emission
*/
double ME_Higgs_current_unof(
int aptype, int bptype,
CLHEP::HepLorentzVector const & punof,
CLHEP::HepLorentzVector const & pn,
CLHEP::HepLorentzVector const & pb,
CLHEP::HepLorentzVector const & p1,
CLHEP::HepLorentzVector const & pa,
CLHEP::HepLorentzVector const & qH, // t-channel momentum before Higgs
CLHEP::HepLorentzVector const & qHp1, // t-channel momentum after Higgs
double mt, bool include_bottom, double mb
){
if (aptype==21&&bptype!=21) {
if (bptype > 0)
return jM2unogqHg(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unogqbarHg(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
else { // they are both quark
if (bptype>0) {
if (aptype>0)
return jM2unogqHQ(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unogqHQbar(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
else {
if (aptype>0)
return jM2unogqbarHQ(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unogqbarHQbar(punof,pn,pb,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
}
throw std::logic_error("unknown particle types");
}
/** \brief Current matrix element squared with Higgs and unordered backward emission
* @param aptype Particle A PDG ID
* @param bptype Particle B PDG ID
* @param pn Particle n Momentum
* @param pb Particle b Momentum
* @param punob Unordered back Particle Momentum
* @param p1 Particle 1 Momentum
* @param pa Particle a Momentum
* @param qH t-channel momentum before Higgs
* @param qHp1 t-channel momentum after Higgs
* @returns ME Squared with Higgs and unordered backward emission
*/
double ME_Higgs_current_unob(
int aptype, int bptype,
CLHEP::HepLorentzVector const & pn,
CLHEP::HepLorentzVector const & pb,
CLHEP::HepLorentzVector const & punob,
CLHEP::HepLorentzVector const & p1,
CLHEP::HepLorentzVector const & pa,
CLHEP::HepLorentzVector const & qH, // t-channel momentum before Higgs
CLHEP::HepLorentzVector const & qHp1, // t-channel momentum after Higgs
double mt, bool include_bottom, double mb
){
if (bptype==21&&aptype!=21) {
if (aptype > 0)
return jM2unobgHQg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unobgHQbarg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
else { // they are both quark
if (aptype>0) {
if (bptype>0)
return jM2unobqHQg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unobqbarHQg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
else {
if (bptype>0)
return jM2unobqHQbarg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
else
return jM2unobqbarHQbarg(pn,pb,punob,p1,pa,-qHp1,-qH,mt,include_bottom,mb);
}
}
throw std::logic_error("unknown particle types");
}
CLHEP::HepLorentzVector to_HepLorentzVector(RHEJ::Particle const & particle){
return {particle.p.px(), particle.p.py(), particle.p.pz(), particle.p.E()};
}
} // namespace anonymous
namespace RHEJ{
MatrixElement::MatrixElement(
std::function<double (double)> alpha_s,
MatrixElementConfig conf
):
alpha_s_{std::move(alpha_s)},
param_{std::move(conf)}
{}
double MatrixElement::operator()(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
return tree(
mur,
incoming, outgoing,
check_momenta
)*virtual_corrections(
mur,
incoming, outgoing
);
}
double MatrixElement::tree_kin(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
assert(
std::is_sorted(
incoming.begin(), incoming.end(),
[](Particle o1, Particle o2){return o1.p.pz()<o2.p.pz();}
)
);
assert(std::is_sorted(outgoing.begin(), outgoing.end(), rapidity_less{}));
auto AWZH_boson = std::find_if(
begin(outgoing), end(outgoing),
[](Particle const & p){return is_AWZH_boson(p);}
);
if(AWZH_boson == end(outgoing)){
return tree_kin_jets(incoming, outgoing, check_momenta);
}
switch(AWZH_boson->type){
case pid::Higgs: {
static constexpr double mH = 125.;
const double alpha_s_mH = alpha_s_(mH);
return alpha_s_mH*alpha_s_mH/(256.*pow(M_PI, 5))*tree_kin_Higgs(
incoming, outgoing, check_momenta
);
}
// TODO
case pid::Wp:
case pid::Wm:
case pid::photon:
case pid::Z:
default:
throw std::logic_error("Emission of boson of unsupported type");
}
}
namespace{
constexpr int extremal_jet_idx = 1;
constexpr int no_extremal_jet_idx = 0;
bool treat_as_extremal(Particle const & parton){
return parton.p.user_index() == extremal_jet_idx;
}
template<class InputIterator>
double FKL_ladder_weight(
InputIterator begin_gluon, InputIterator end_gluon,
CLHEP::HepLorentzVector const & q0,
CLHEP::HepLorentzVector const & pa, CLHEP::HepLorentzVector const & pb,
CLHEP::HepLorentzVector const & p1, CLHEP::HepLorentzVector const & pn
){
double wt = 1;
auto qi = q0;
for(auto gluon_it = begin_gluon; gluon_it != end_gluon; ++gluon_it){
assert(gluon_it->type == pid::gluon);
const auto g = to_HepLorentzVector(*gluon_it);
const auto qip1 = qi - g;
if(treat_as_extremal(*gluon_it)){
wt *= C2Lipatovots(qip1, qi, pa, pb)*C_A;
} else{
wt *= C2Lipatovots(qip1, qi, pa, pb, p1, pn)*C_A;
}
qi = qip1;
}
return wt;
}
} // namespace anonymous
std::vector<Particle> MatrixElement::tag_extremal_jet_partons(
std::array<Particle, 2> const & incoming,
std::vector<Particle> out_partons, bool check_momenta
) const{
if(!check_momenta){
for(auto & parton: out_partons){
parton.p.set_user_index(no_extremal_jet_idx);
}
return out_partons;
}
fastjet::ClusterSequence cs(to_PseudoJet(out_partons), param_.jet_param.def);
const auto jets = sorted_by_rapidity(cs.inclusive_jets(param_.jet_param.min_pt));
assert(jets.size() >= 2);
auto most_backward = begin(jets);
auto most_forward = end(jets) - 1;
// skip jets caused by unordered emission
if(has_unob_gluon(incoming, out_partons)){
assert(jets.size() >= 3);
++most_backward;
}
else if(has_unof_gluon(incoming, out_partons)){
assert(jets.size() >= 3);
--most_forward;
}
const auto extremal_jet_indices = cs.particle_jet_indices(
{*most_backward, *most_forward}
);
assert(extremal_jet_indices.size() == out_partons.size());
for(size_t i = 0; i < out_partons.size(); ++i){
assert(RHEJ::is_parton(out_partons[i]));
const int idx = (extremal_jet_indices[i]>=0)?
extremal_jet_idx:
no_extremal_jet_idx;
out_partons[i].p.set_user_index(idx);
}
return out_partons;
}
double MatrixElement::tree_kin_jets(
std::array<Particle, 2> const & incoming,
std::vector<Particle> partons,
bool check_momenta
) const {
partons = tag_extremal_jet_partons(incoming, partons, check_momenta);
if(has_unob_gluon(incoming, partons) || has_unof_gluon(incoming, partons)){
throw std::logic_error("unordered emission not implemented for pure jets");
}
const auto pa = to_HepLorentzVector(incoming[0]);
const auto pb = to_HepLorentzVector(incoming[1]);
const auto p1 = to_HepLorentzVector(partons.front());
const auto pn = to_HepLorentzVector(partons.back());
return ME_current(
incoming[0].type, incoming[1].type,
pn, pb, p1, pa
)/(4*(N_C*N_C - 1))*FKL_ladder_weight(
begin(partons) + 1, end(partons) - 1,
pa - p1, pa, pb, p1, pn
);
}
double MatrixElement::tree_kin_Higgs(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
if(has_uno_gluon(incoming, outgoing)){
return tree_kin_Higgs_between(incoming, outgoing, check_momenta);
}
if(outgoing.front().type == pid::Higgs){
return tree_kin_Higgs_first(incoming, outgoing, check_momenta);
}
if(outgoing.back().type == pid::Higgs){
return tree_kin_Higgs_last(incoming, outgoing, check_momenta);
}
return tree_kin_Higgs_between(incoming, outgoing, check_momenta);
}
double MatrixElement::MH2_forwardH(
RHEJ::ParticleID id,
CLHEP::HepLorentzVector p1out, CLHEP::HepLorentzVector p1in,
CLHEP::HepLorentzVector p2out, CLHEP::HepLorentzVector p2in,
CLHEP::HepLorentzVector pH,
double t1, double t2
) const{
ignore(p2out, p2in);
const double shat = p1in.invariantMass2(p2in);
assert(RHEJ::is_parton(id));
if(id != RHEJ::pid::gluon){
return 9./2.*shat*shat*C2qHqm(p1in,p1out,pH)/(t1*t2);
}
// gluon case
#ifdef RHEJ_BUILD_WITH_QCDLOOP
if(!param_.Higgs_coupling.use_impact_factors){
return C_A/C_F*1./(16*M_PI*M_PI)*t1/t2*MH2gq_outsideH(
p1out, p1in, p2out, p2in, pH,
param_.Higgs_coupling.mt, param_.Higgs_coupling.include_bottom,
param_.Higgs_coupling.mb
);
}
#endif
return 9./2.*shat*shat*(
C2gHgp(p1in,p1out,pH) + C2gHgm(p1in,p1out,pH)
)/(t1*t2);
}
double MatrixElement::tree_kin_Higgs_first(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
assert(outgoing.front().type == pid::Higgs);
const auto pH = to_HepLorentzVector(outgoing.front());
const auto partons = tag_extremal_jet_partons(
incoming,
std::vector<Particle>(begin(outgoing) + 1, end(outgoing)),
check_momenta
);
const auto pa = to_HepLorentzVector(incoming[0]);
const auto pb = to_HepLorentzVector(incoming[1]);
const auto p1 = to_HepLorentzVector(partons.front());
const auto pn = to_HepLorentzVector(partons.back());
const auto q0 = pa - p1 - pH;
const double t1 = q0.m2();
const double t2 = (pn - pb).m2();
double wt = MH2_forwardH(
incoming[0].type, p1, pa, pn, pb, pH,
t1, t2
)*FKL_ladder_weight(
begin(partons) + 1, end(partons) - 1,
q0, pa, pb, p1, pn
);
for(auto const & inc: incoming){
if(inc.type != pid::gluon) wt *= C_F/C_A;
}
return wt;
}
double MatrixElement::tree_kin_Higgs_last(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
assert(outgoing.back().type == pid::Higgs);
const auto pH = to_HepLorentzVector(outgoing.back());
const auto partons = tag_extremal_jet_partons(
incoming,
std::vector<Particle>(begin(outgoing), end(outgoing) - 1),
check_momenta
);
const auto pa = to_HepLorentzVector(incoming[0]);
const auto pb = to_HepLorentzVector(incoming[1]);
auto p1 = to_HepLorentzVector(partons.front());
const auto pn = to_HepLorentzVector(partons.back());
auto q0 = pa - p1;
const double t1 = q0.m2();
const double t2 = (pn + pH - pb).m2();
double wt = MH2_forwardH(
incoming[1].type, pn, pb, p1, pa, pH,
t2, t1
)*FKL_ladder_weight(
begin(partons) + 1, end(partons) - 1,
q0, pa, pb, p1, pn
);
for(auto const & inc: incoming){
if(inc.type != pid::gluon) wt *= C_F/C_A;
}
return wt;
}
double MatrixElement::tree_kin_Higgs_between(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
const auto the_Higgs = std::find_if(
begin(outgoing), end(outgoing),
[](Particle const & s){ return s.type == pid::Higgs; }
);
assert(the_Higgs != end(outgoing));
const auto pH = to_HepLorentzVector(*the_Higgs);
std::vector<Particle> partons(begin(outgoing), the_Higgs);
partons.insert(end(partons), the_Higgs + 1, end(outgoing));
partons = tag_extremal_jet_partons(incoming, partons, check_momenta);
const auto pa = to_HepLorentzVector(incoming[0]);
const auto pb = to_HepLorentzVector(incoming[1]);
auto p1 = to_HepLorentzVector(
partons[has_unob_gluon(incoming, outgoing)?1:0]
);
auto pn = to_HepLorentzVector(
partons[partons.size() - (has_unof_gluon(incoming, outgoing)?2:1)]
);
auto first_after_Higgs = begin(partons) + (the_Higgs-begin(outgoing));
assert(
(first_after_Higgs == end(partons) && has_unob_gluon(incoming, outgoing))
|| first_after_Higgs->rapidity() >= the_Higgs->rapidity()
);
assert(
(first_after_Higgs == begin(partons) && has_unof_gluon(incoming, outgoing))
|| (first_after_Higgs-1)->rapidity() <= the_Higgs->rapidity()
);
// always treat the Higgs as if it were in between the extremal FKL partons
if(first_after_Higgs == begin(partons)) ++first_after_Higgs;
else if(first_after_Higgs == end(partons)) --first_after_Higgs;
// t-channel momentum before Higgs
auto qH = pa;
for(auto parton_it = begin(partons); parton_it != first_after_Higgs; ++parton_it){
qH -= to_HepLorentzVector(*parton_it);
}
auto q0 = pa - p1;
auto begin_ladder = begin(partons) + 1;
auto end_ladder = end(partons) - 1;
double current_factor;
if(has_unob_gluon(incoming, outgoing)){
current_factor = 9./2.*ME_Higgs_current_unob(
incoming[0].type, incoming[1].type,
pn, pb, to_HepLorentzVector(partons.front()), p1, pa, qH, qH - pH,
param_.Higgs_coupling.mt,
param_.Higgs_coupling.include_bottom, param_.Higgs_coupling.mb
);
const auto p_unob = to_HepLorentzVector(partons.front());
q0 -= p_unob;
p1 += p_unob;
++begin_ladder;
}
else if(has_unof_gluon(incoming, outgoing)){
current_factor = 9./2.*ME_Higgs_current_unof(
incoming[0].type, incoming[1].type,
to_HepLorentzVector(partons.back()), pn, pb, p1, pa, qH, qH - pH,
param_.Higgs_coupling.mt,
param_.Higgs_coupling.include_bottom, param_.Higgs_coupling.mb
);
pn += to_HepLorentzVector(partons.back());
--end_ladder;
}
else{
current_factor = ME_Higgs_current(
incoming[0].type, incoming[1].type,
pn, pb, p1, pa, qH, qH - pH,
param_.Higgs_coupling.mt,
param_.Higgs_coupling.include_bottom, param_.Higgs_coupling.mb
);
}
const double ladder_factor = FKL_ladder_weight(
begin_ladder, first_after_Higgs,
q0, pa, pb, p1, pn
)*FKL_ladder_weight(
first_after_Higgs, end_ladder,
qH - pH, pa, pb, p1, pn
);
return current_factor*9./8.*ladder_factor;
}
double MatrixElement::tree_param_partons(
double alpha_s, double mur,
std::vector<Particle> const & partons
) const{
const double gs2 = 4.*M_PI*alpha_s;
double wt = std::pow(gs2, partons.size());
if(param_.log_correction){
// use alpha_s(q_perp), evolved to mur
assert(partons.size() >= 2);
for(size_t i = 1; i < partons.size()-1; ++i){
wt *= 1 + alpha_s/(2*M_PI)*beta0*log(mur/partons[i].p.perp());
}
}
return wt;
}
double MatrixElement::tree_param(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing
) const{
const double alpha_s = alpha_s_(mur);
if(has_unob_gluon(incoming, outgoing)){
return 4*M_PI*alpha_s*tree_param_partons(
alpha_s, mur, filter_partons({begin(outgoing) + 1, end(outgoing)})
);
}
if(has_unof_gluon(incoming, outgoing)){
return 4*M_PI*alpha_s*tree_param_partons(
alpha_s, mur, filter_partons({begin(outgoing), end(outgoing) - 1})
);
}
return tree_param_partons(alpha_s, mur, filter_partons(outgoing));
}
double MatrixElement::tree(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const {
return tree_param(mur, incoming, outgoing)*tree_kin(
incoming, outgoing, check_momenta
);
}
} // namespace RHEJ
diff --git a/src/PhaseSpacePoint.cc b/src/PhaseSpacePoint.cc
index 5067a0b..d63ed7c 100644
--- a/src/PhaseSpacePoint.cc
+++ b/src/PhaseSpacePoint.cc
@@ -1,535 +1,535 @@
#include "RHEJ/PhaseSpacePoint.hh"
#include <random>
#include <CLHEP/Random/Randomize.h>
#include <CLHEP/Random/RanluxEngine.h>
#include "RHEJ/Constants.hh"
#include "RHEJ/resummation_jet_momenta.hh"
#include "RHEJ/Jacobian.hh"
#include "RHEJ/uno.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.hh"
#include "RHEJ/kinematics.hh"
namespace RHEJ{
namespace {
constexpr int max_jet_user_idx = PhaseSpacePoint::ng_max;
bool is_nonjet_parton(fastjet::PseudoJet const & parton){
assert(parton.user_index() != -1);
return parton.user_index() > max_jet_user_idx;
}
bool is_jet_parton(fastjet::PseudoJet const & parton){
assert(parton.user_index() != -1);
return parton.user_index() <= max_jet_user_idx;
}
// user indices for partons with extremal rapidity
constexpr int unob_idx = -5;
constexpr int unof_idx = -4;
constexpr int backward_FKL_idx = -3;
constexpr int forward_FKL_idx = -2;
}
namespace {
double estimate_ng_mean(std::vector<fastjet::PseudoJet> const & Born_jets){
const double delta_y =
Born_jets.back().rapidity() - Born_jets.front().rapidity();
assert(delta_y > 0);
// Formula derived from fit in reversed HEJ intro paper
return 0.975052*delta_y;
}
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::cluster_jets(
std::vector<fastjet::PseudoJet> const & partons
) const{
fastjet::ClusterSequence cs(partons, param_.jet_param.def);
return cs.inclusive_jets(param_.jet_param.min_pt);
}
bool PhaseSpacePoint::pass_resummation_cuts(
std::vector<fastjet::PseudoJet> const & jets
) const{
return cluster_jets(jets).size() == jets.size();
}
int PhaseSpacePoint::sample_ng(std::vector<fastjet::PseudoJet> const & Born_jets){
const double ng_mean = estimate_ng_mean(Born_jets);
std::poisson_distribution<int> dist(ng_mean);
const int ng = dist(ran_.get());
assert(ng >= 0);
assert(ng < ng_max);
weight_ *= std::tgamma(ng + 1)*std::exp(ng_mean)*std::pow(ng_mean, -ng);
return ng;
}
void PhaseSpacePoint::copy_AWZH_boson_from(Event const & event){
auto const & from = event.outgoing();
const auto AWZH_boson = std::find_if(
begin(from), end(from),
[](Particle const & p){ return is_AWZH_boson(p); }
);
if(AWZH_boson == end(from)) return;
auto insertion_point = std::lower_bound(
begin(outgoing_), end(outgoing_), *AWZH_boson, rapidity_less{}
);
outgoing_.insert(insertion_point, *AWZH_boson);
// copy decay products
const int idx = std::distance(begin(from), AWZH_boson);
const auto decay_it = event.decays().find(idx);
if(decay_it != end(event.decays())){
const int new_idx = std::distance(begin(outgoing_), insertion_point);
assert(outgoing_[new_idx].type == AWZH_boson->type);
decays_.emplace(new_idx, decay_it->second);
}
assert(std::is_sorted(begin(outgoing_), end(outgoing_), rapidity_less{}));
}
PhaseSpacePoint::PhaseSpacePoint(
Event const & ev, PhaseSpacePointConfig conf, RHEJ::RNG & ran
):
unob_{has_unob_gluon(ev.incoming(), ev.outgoing())},
unof_{!unob_ && has_unof_gluon(ev.incoming(), ev.outgoing())},
param_{std::move(conf)},
ran_{ran},
splitter_{param_.jet_param.def.R(), param_.jet_param.def, param_.jet_param.min_pt, ran}
{
weight_ = 1;
const auto Born_jets = sorted_by_rapidity(ev.jets());
const int ng = sample_ng(Born_jets);
weight_ /= std::tgamma(ng + 1);
const int ng_jets = sample_ng_jets(ng, Born_jets);
std::vector<fastjet::PseudoJet> out_partons = gen_non_jet(
ng - ng_jets, CMINPT, param_.jet_param.min_pt
);
{
const auto qperp = std::accumulate(
begin(out_partons), end(out_partons),
fastjet::PseudoJet{}
);
const auto jets = reshuffle(Born_jets, qperp);
if(weight_ == 0.) return;
if(! pass_resummation_cuts(jets)){
weight_ = 0.;
return;
}
std::vector<fastjet::PseudoJet> jet_partons = split(jets, ng_jets);
if(weight_ == 0.) return;
rescale_rapidities(
out_partons,
most_backward_FKL(jet_partons).rapidity(),
most_forward_FKL(jet_partons).rapidity()
);
if(! cluster_jets(out_partons).empty()){
weight_ = 0.;
return;
}
std::sort(begin(out_partons), end(out_partons), rapidity_less{});
assert(
std::is_sorted(begin(jet_partons), end(jet_partons), rapidity_less{})
);
const auto first_jet_parton = out_partons.insert(
end(out_partons), begin(jet_partons), end(jet_partons)
);
std::inplace_merge(
begin(out_partons), first_jet_parton, end(out_partons), rapidity_less{}
);
}
if(! jets_ok(Born_jets, out_partons)){
weight_ = 0.;
return;
}
weight_ *= phase_space_normalisation(Born_jets.size(), out_partons.size());
outgoing_.reserve(out_partons.size() + 1); // one slot for possible A, W, Z, H
for(auto & p: out_partons){
outgoing_.emplace_back(Particle{pid::gluon, std::move(p)});
}
most_backward_FKL(outgoing_).type = ev.incoming().front().type;
most_forward_FKL(outgoing_).type = ev.incoming().back().type;
copy_AWZH_boson_from(ev);
assert(!outgoing_.empty());
reconstruct_incoming(ev.incoming());
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::gen_non_jet(
int count, double ptmin, double ptmax
){
// heuristic parameters for pt sampling
const double ptpar = 1.3 + count/5.;
const double temp1 = atan((ptmax - ptmin)/ptpar);
std::vector<fastjet::PseudoJet> partons(count);
for(size_t i = 0; i < (size_t) count; ++i){
const double r1 = ran_.get().flat();
const double pt = ptmin + ptpar*tan(r1*temp1);
const double temp2 = cos(r1*temp1);
const double phi = 2*M_PI*ran_.get().flat();
weight_ *= 2.0*M_PI*pt*ptpar*temp1/(temp2*temp2);
// we don't know the allowed rapidity span yet,
// set a random value to be rescaled later on
const double y = ran_.get().flat();
partons[i].reset_PtYPhiM(pt, y, phi);
// Set user index higher than any jet-parton index
// in order to assert that these are not inside jets
partons[i].set_user_index(i + 1 + ng_max);
assert(ptmin-1e-5 <= partons[i].pt() && partons[i].pt() <= ptmax+1e-5);
}
assert(std::all_of(partons.cbegin(), partons.cend(), is_nonjet_parton));
return partons;
}
void PhaseSpacePoint::rescale_rapidities(
std::vector<fastjet::PseudoJet> & partons,
double ymin, double ymax
){
constexpr double ep = 1e-7;
for(auto & parton: partons){
assert(0 <= parton.rapidity() && parton.rapidity() <= 1);
const double dy = ymax - ymin - 2*ep;
const double y = ymin + ep + dy*parton.rapidity();
parton.reset_momentum_PtYPhiM(parton.pt(), y, parton.phi());
weight_ *= dy;
assert(ymin <= parton.rapidity() && parton.rapidity() <= ymax);
}
}
namespace {
template<typename T, typename... Rest>
auto min(T const & a, T const & b, Rest&&... r) {
using std::min;
return min(a, min(b, std::forward<Rest>(r)...));
}
}
double PhaseSpacePoint::probability_in_jet(
std::vector<fastjet::PseudoJet> const & Born_jets
) const{
assert(std::is_sorted(begin(Born_jets), end(Born_jets), rapidity_less{}));
assert(Born_jets.size() >= 2);
const double dy =
Born_jets.back().rapidity() - Born_jets.front().rapidity();
const double R = param_.jet_param.def.R();
const int njets = Born_jets.size();
const double p_J_y_large = (njets-1)*R*R/(2.*dy);
const double p_J_y0 = njets*R/M_PI;
return min(p_J_y_large, p_J_y0, 1.);
}
int PhaseSpacePoint::sample_ng_jets(
int ng, std::vector<fastjet::PseudoJet> const & Born_jets
){
const double p_J = probability_in_jet(Born_jets);
std::binomial_distribution<> bin_dist(ng, p_J);
const int ng_J = bin_dist(ran_.get());
weight_ *= std::pow(p_J, -ng_J)*std::pow(1 - p_J, ng_J - ng);
return ng_J;
}
std::vector<fastjet::PseudoJet>
PhaseSpacePoint::reshuffle(
std::vector<fastjet::PseudoJet> const & Born_jets,
fastjet::PseudoJet const & q
){
if(q == fastjet::PseudoJet{0, 0, 0, 0}) return Born_jets;
std::vector<fastjet::PseudoJet> jets = resummation_jet_momenta(Born_jets, q);
if(jets.empty()){
weight_ = 0;
return {};
}
// transform delta functions to integration over resummation momenta
weight_ /= Jacobian(jets, q);
return jets;
}
std::vector<int> PhaseSpacePoint::distribute_jet_partons(
int ng_jets, std::vector<fastjet::PseudoJet> const & jets
){
size_t first_valid_jet = 0;
size_t num_valid_jets = jets.size();
const double R_eff = 5./3.*param_.jet_param.def.R();
// if there is an unordered jet too far away from the FKL jets
// then extra gluon constituents of the unordered jet would
// violate the FKL rapidity ordering
if(unob_ && jets[0].delta_R(jets[1]) > R_eff){
++first_valid_jet;
--num_valid_jets;
}
else if(unof_ && jets[jets.size()-1].delta_R(jets[jets.size()-2]) > R_eff){
--num_valid_jets;
}
std::vector<int> np(jets.size(), 1);
for(int i = 0; i < ng_jets; ++i){
++np[first_valid_jet + ran_.get().flat() * num_valid_jets];
}
weight_ *= std::pow(num_valid_jets, ng_jets);
return np;
}
#ifndef NDEBUG
namespace{
bool tagged_FKL_backward(
std::vector<fastjet::PseudoJet> const & jet_partons
){
return std::find_if(
begin(jet_partons), end(jet_partons),
[](fastjet::PseudoJet const & p){
return p.user_index() == backward_FKL_idx;
}
) != end(jet_partons);
}
bool tagged_FKL_forward(
std::vector<fastjet::PseudoJet> const & jet_partons
){
// the most forward FKL parton is most likely near the end of jet_partons;
// start search from there
return std::find_if(
jet_partons.rbegin(), jet_partons.rend(),
[](fastjet::PseudoJet const & p){
return p.user_index() == forward_FKL_idx;
}
) != jet_partons.rend();
}
bool tagged_FKL_extremal(
std::vector<fastjet::PseudoJet> const & jet_partons
){
return tagged_FKL_backward(jet_partons) && tagged_FKL_forward(jet_partons);
}
} // namespace anonymous
#endif
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
std::vector<fastjet::PseudoJet> const & jets,
int ng_jets
){
return split(jets, distribute_jet_partons(ng_jets, jets));
}
bool PhaseSpacePoint::pass_extremal_cuts(
fastjet::PseudoJet const & ext_parton,
fastjet::PseudoJet const & jet
) const{
if(ext_parton.pt() < param_.min_extparton_pt) return false;
return (ext_parton - jet).pt()/jet.pt() < param_.max_ext_soft_pt_fraction;
}
std::vector<fastjet::PseudoJet> PhaseSpacePoint::split(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<int> const & np
){
assert(! jets.empty());
assert(jets.size() == np.size());
assert(pass_resummation_cuts(jets));
const size_t most_backward_FKL_idx = 0 + unob_;
const size_t most_forward_FKL_idx = jets.size() - 1 - unof_;
std::vector<fastjet::PseudoJet> jet_partons;
// randomly distribute jet gluons among jets
for(size_t i = 0; i < jets.size(); ++i){
weight_ *= splitter_.Split(jets[i], np[i]);
if(weight_ == 0) return {};
assert(
std::all_of(
begin(splitter_.get_jcons()), end(splitter_.get_jcons()),
is_jet_parton
)
);
const auto first_new_parton = jet_partons.insert(
end(jet_partons),
begin(splitter_.get_jcons()), end(splitter_.get_jcons())
);
// mark uno and extremal FKL emissions here so we can check
// their position once all emissions are generated
auto extremal = end(jet_partons);
if((unob_ && i == 0) || i == most_backward_FKL_idx){
// unordered or FKL backward emission
extremal = std::min_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(
(i == most_backward_FKL_idx)?backward_FKL_idx:unob_idx
);
}
else if((unof_ && i == jets.size() - 1) || i == most_forward_FKL_idx){
// unordered or FKL forward emission
extremal = std::max_element(
first_new_parton, end(jet_partons), rapidity_less{}
);
extremal->set_user_index(
(i == most_forward_FKL_idx)?forward_FKL_idx:unof_idx
);
}
if(
extremal != end(jet_partons)
&& !pass_extremal_cuts(*extremal, jets[i])
){
weight_ = 0;
return {};
}
}
assert(tagged_FKL_extremal(jet_partons));
std::sort(begin(jet_partons), end(jet_partons), rapidity_less{});
if(
!extremal_ok(jet_partons)
|| !split_preserved_jets(jets, jet_partons)
){
weight_ = 0.;
return {};
}
return jet_partons;
}
bool PhaseSpacePoint::extremal_ok(
std::vector<fastjet::PseudoJet> const & partons
) const{
assert(std::is_sorted(begin(partons), end(partons), rapidity_less{}));
if(unob_ && partons.front().user_index() != unob_idx) return false;
if(unof_ && partons.back().user_index() != unof_idx) return false;
return
most_backward_FKL(partons).user_index() == backward_FKL_idx
&& most_forward_FKL(partons).user_index() == forward_FKL_idx;
}
bool PhaseSpacePoint::split_preserved_jets(
std::vector<fastjet::PseudoJet> const & jets,
std::vector<fastjet::PseudoJet> const & jet_partons
) const{
assert(std::is_sorted(begin(jets), end(jets), rapidity_less{}));
const auto split_jets = sorted_by_rapidity(cluster_jets(jet_partons));
// this can happen if two overlapping jets
// are both split into more than one parton
if(split_jets.size() != jets.size()) return false;
for(size_t i = 0; i < split_jets.size(); ++i){
// this can happen if there are two overlapping jets
// and a parton is assigned to the "wrong" jet
if(!nearby_ep(jets[i].rapidity(), split_jets[i].rapidity(), 1e-2)){
return false;
}
}
return true;
}
template<class Particle>
Particle const & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> const & partons
) const{
return partons[0 + unob_];
}
template<class Particle>
Particle const & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> const & partons
) const{
const size_t idx = partons.size() - 1 - unof_;
assert(idx < partons.size());
return partons[idx];
}
template<class Particle>
Particle & PhaseSpacePoint::most_backward_FKL(
std::vector<Particle> & partons
) const{
return partons[0 + unob_];
}
template<class Particle>
Particle & PhaseSpacePoint::most_forward_FKL(
std::vector<Particle> & partons
) const{
const size_t idx = partons.size() - 1 - unof_;
assert(idx < partons.size());
return partons[idx];
}
namespace {
bool contains_idx(
fastjet::PseudoJet const & jet, fastjet::PseudoJet const & parton
){
auto const & constituents = jet.constituents();
const int idx = parton.user_index();
return std::find_if(
begin(constituents), end(constituents),
[idx](fastjet::PseudoJet const & con){return con.user_index() == idx;}
) != end(constituents);
}
}
/**
* final jet test:
* - number of jets must match Born kinematics
* - no partons designated as nonjet may end up inside jets
* - all other outgoing partons *must* end up inside jets
* - the extremal (in rapidity) partons must be inside the extremal jets
* - rapidities must be the same (by construction)
*/
bool PhaseSpacePoint::jets_ok(
std::vector<fastjet::PseudoJet> const & Born_jets,
std::vector<fastjet::PseudoJet> const & partons
) const{
fastjet::ClusterSequence cs(partons, param_.jet_param.def);
const auto jets = sorted_by_rapidity(cs.inclusive_jets(param_.jet_param.min_pt));
if(jets.size() != Born_jets.size()) return false;
int in_jet = 0;
for(size_t i = 0; i < jets.size(); ++i){
assert(jets[i].has_constituents());
for(auto && parton: jets[i].constituents()){
if(is_nonjet_parton(parton)) return false;
}
in_jet += jets[i].constituents().size();
}
const int expect_in_jet = std::count_if(
partons.cbegin(), partons.cend(), is_jet_parton
);
if(in_jet != expect_in_jet) return false;
// note that PseudoJet::contains does not work here
if(! (
contains_idx(most_backward_FKL(jets), most_backward_FKL(partons))
&& contains_idx(most_forward_FKL(jets), most_forward_FKL(partons))
)) return false;
if(unob_ && !contains_idx(jets.front(), partons.front())) return false;
if(unof_ && !contains_idx(jets.back(), partons.back())) return false;
for(size_t i = 0; i < jets.size(); ++i){
assert(nearby_ep(jets[i].rapidity(), Born_jets[i].rapidity(), 1e-2));
}
return true;
}
void PhaseSpacePoint::reconstruct_incoming(
std::array<Particle, 2> const & Born_incoming
){
std::tie(incoming_[0].p, incoming_[1].p) = incoming_momenta(outgoing_);
for(size_t i = 0; i < incoming_.size(); ++i){
incoming_[i].type = Born_incoming[i].type;
}
assert(momentum_conserved());
}
double PhaseSpacePoint::phase_space_normalisation(
int num_Born_jets, int num_out_partons
) const{
return pow(16*pow(M_PI,3), num_Born_jets - num_out_partons);
}
bool PhaseSpacePoint::momentum_conserved() const{
fastjet::PseudoJet diff;
for(auto const & in: incoming()) diff += in.p;
const double norm = diff.E();
for(auto const & out: outgoing()) diff -= out.p;
return nearby(diff, fastjet::PseudoJet{}, norm);
}
} //namespace RHEJ
diff --git a/src/resummation_jet_momenta.cc b/src/resummation_jet_momenta.cc
index c2ff1c5..d2ecc08 100644
--- a/src/resummation_jet_momenta.cc
+++ b/src/resummation_jet_momenta.cc
@@ -1,173 +1,173 @@
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <vector>
#include <array>
#include <algorithm>
#include "RHEJ/resummation_jet_momenta.hh"
-#include "RHEJ/debug.hh"
+#include "RHEJ/utility.hh"
#include "RHEJ/gsl_wrapper.hh"
namespace {
using namespace gsl;
enum Coordinate{
x = 0,
y = 1,
};
struct BornParameters{
std::vector< std::array<double, 2> > pt_born;
std::array<double, 2> q;
};
double pt_abs(double px, double py){
return sqrt(px*px + py*py);
}
//! calculate momentum difference for jets
/**
* After reshuffling, we have the condition
* Delta = pt_born - pt_res + q* |pt_res|/P_perp = 0
* for each jet, where P_perp is the sum of |pt_res| over all jets
* This function calculates Delta and stores the result in diff
*
* Since the gsl_vectors are one-dimensional, indices are a bit funny;
* diff->data[2*i + X]
* corresponds to the X component of the momentum vector for jet i
*/
int calc_jet_diff(const gsl_vector * pt_resum, void *data, gsl_vector * diff){
assert(diff->size == pt_resum->size);
assert(diff->size % 2 == 0);
auto param = static_cast<BornParameters const *>(data);
auto const & pt_born = param->pt_born;
auto pt_res = pt_resum->data;
auto const & q = param->q;
const size_t n_jets = pt_resum->size/2;
double P_perp = 0.;
for(size_t jet = 0; jet < n_jets; ++jet){
P_perp += pt_abs(pt_res[2*jet + x], pt_res[2*jet + y]);
}
for(size_t jet = 0; jet < n_jets; ++jet){
const double pt_res_abs = pt_abs(pt_res[2*jet + x], pt_res[2*jet + y]);
for(Coordinate X: {x,y}){
diff->data[2*jet + X] =
pt_born[jet][X] - pt_res[2*jet + X] - q[X]*pt_res_abs/P_perp;
}
}
return GSL_SUCCESS;
}
// computes resummation jet pt from Born jet pt
// if this fails an empty vector is returned
std::vector< std::array<double ,2> > reshuffle(BornParameters const & p){
constexpr int max_iterations = 1000;
const size_t n_jets = p.pt_born.size();
gsl_multiroot_function f = {
&calc_jet_diff, 2*n_jets,
const_cast<BornParameters *>(&p)
};
Vector pt_resum{2*n_jets};
// initial values for solver - resummation pt = Born pt
for (size_t jet = 0; jet < n_jets; ++jet) {
pt_resum[2*jet+x] = p.pt_born[jet][x];
pt_resum[2*jet+y] = p.pt_born[jet][y];
}
MultirootFsolver solver{
gsl_multiroot_fsolver_hybrids,
&f, std::move(pt_resum)
};
// solve equations
int status = GSL_CONTINUE;
for(
int iterations = 1;
status == GSL_CONTINUE && iterations < max_iterations;
++iterations
){
status = solver.iterate();
if(status == GSL_EBADFUNC || status == GSL_ENOPROG) return {};
status = solver.test_residual(1e-7);
}
if(status != GSL_SUCCESS) return {};
std::vector< std::array<double ,2> > res_pt(n_jets);
for(size_t jet = 0; jet < n_jets; ++jet) {
res_pt[jet][x] = gsl_vector_get(solver.x(), 2*jet + x);
res_pt[jet][y] = gsl_vector_get(solver.x(), 2*jet + y);
}
return res_pt;
}
// check that pt_i^B == pt_i + qt_i for each jet
void assert_pt_conservation(
std::vector<fastjet::PseudoJet> const & jetvects,
fastjet::PseudoJet const & qperp,
std::vector<fastjet::PseudoJet> const & shuffledmomenta
){
- ignore(jetvects, qperp, shuffledmomenta);
+ RHEJ::ignore(jetvects, qperp, shuffledmomenta);
#ifndef NDEBUG
assert(jetvects.size() == shuffledmomenta.size());
double Pperp = 0;
for(auto const & p: shuffledmomenta) Pperp += p.perp();
for(size_t i = 0; i < jetvects.size(); ++i){
const auto qperp_i = qperp*shuffledmomenta[i].perp()/Pperp;
const auto pdiff = jetvects[i] - shuffledmomenta[i] - qperp_i;
assert(nearby_ep(pdiff.px(), 0, 1e-5));
assert(nearby_ep(pdiff.py(), 0, 1e-5));
}
#endif
}
}
namespace RHEJ{
std::vector<fastjet::PseudoJet> resummation_jet_momenta(
std::vector<fastjet::PseudoJet> const & p_born,
fastjet::PseudoJet const & q
) {
std::vector<fastjet::PseudoJet> p_res;
p_res.reserve(p_born.size());
BornParameters r;
r.q[x] = q.px();
r.q[y] = q.py();
r.pt_born.resize(p_born.size());
for (size_t jet = 0; jet < p_born.size(); ++jet) {
r.pt_born[jet][x] = p_born[jet].px();
r.pt_born[jet][y] = p_born[jet].py();
}
const auto pt_reshuffled = reshuffle(r);
if(pt_reshuffled.empty()) return {};
// Construct the new 4-momenta
for (size_t jet = 0; jet < p_born.size(); ++jet) {
const double px = pt_reshuffled[jet][x];
const double py = pt_reshuffled[jet][y];
const double pperp = sqrt(px*px + py*py);
// keep the rapidities fixed
const double pz = pperp*sinh(p_born[jet].rapidity());
const double E = pperp*cosh(p_born[jet].rapidity());
p_res.emplace_back(px, py, pz, E);
assert(
nearby_ep(
p_res.back().rapidity(),
p_born[jet].rapidity(),
1e-5
)
);
}
assert_pt_conservation(p_born, q, p_res);
return p_res;
}
}

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