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diff --git a/include/RHEJ/MatrixElement.hh b/include/RHEJ/MatrixElement.hh
index ae519aa..e724add 100644
--- a/include/RHEJ/MatrixElement.hh
+++ b/include/RHEJ/MatrixElement.hh
@@ -1,208 +1,207 @@
/** \file
* \brief Contains the MatrixElement Class
*/
#pragma once
#include <functional>
#include "RHEJ/config.hh"
#include "RHEJ/utility.hh"
#include "RHEJ/HiggsCouplingSettings.hh"
#include "CLHEP/Vector/LorentzVector.h"
namespace RHEJ{
//! Class to calculate the squares of matrix elements
class MatrixElement{
public:
/** \brief MatrixElement Constructor
* @param alpha_s Function taking the renormalisation scale
* and returning the strong coupling constant
* @param conf General matrix element settings
*/
MatrixElement(
std::function<double (double)> alpha_s,
MatrixElementConfig conf
);
/**
* \brief regulated HEJ matrix element
* @param mur Value of the renormalisation scale
* @param incoming Incoming particles
* @param outgoing Outgoing particles
* @param check_momenta Special treatment for partons inside extremal jets
* @returns The HEJ matrix element including virtual corrections
*
* cf. eq. (22) in \cite Andersen:2011hs
* Incoming particles should be ordered by ascending z momentum.
* Outgoing particles should be ordered by ascending rapidity.
*
* \internal Relation to standard HEJ Met2: MatrixElement = Met2*shat^2/(pdfta*pdftb)
*/
double operator()(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
//! HEJ tree-level matrix element
/**
* @param mur Value of the renormalisation scale
* @param incoming Incoming particles
* @param outgoing Outgoing particles
* @param check_momenta Special treatment for partons inside extremal jets
* @returns The HEJ matrix element without virtual corrections
*
* cf. eq. (22) in \cite Andersen:2011hs
* Incoming particles should be ordered by ascending z momentum.
* Outgoing particles should be ordered by ascending rapidity.
*/
double tree(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
//! HEJ tree-level matrix element - parametric part
/**
* @param mur Value of the renormalisation scale
* @param incoming Incoming particles
* @param outgoing Outgoing particles
* @returns The parametric part of the tree matrix element
*
* cf. eq. (22) in \cite Andersen:2011hs
*
* The tree level matrix element factorises into a parametric part
* which depends on the theory parameters (alpha_s and scale)
* and a kinematic part comprising the dependence on the particle momenta
* and colour factors. This function returns the former.
*/
double tree_param(
double mur,
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing
) const;
//! HEJ tree-level matrix element - kinematic part
/**
* @param incoming Incoming particles
* @param outgoing Outgoing particles
* @param check_momenta Special treatment for partons inside extremal jets
* @returns The kinematic part of the tree matrix element
*
* cf. eq. (22) in \cite Andersen:2011hs
* Incoming particles should be ordered by ascending z momentum.
* Outgoing particles should be ordered by ascending rapidity.
*
* The tree level matrix element factorises into a parametric part
* which depends on the theory parameters (alpha_s and scale)
* and a kinematic part comprising the dependence on the particle momenta
* and colour factors. This function returns the latter.
*/
double tree_kin(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
/**
* \brief Calculates the Virtual Corrections
* @param mur Value of the renormalisation scale
* @param in Incoming particles
* @param out Outgoing particles
* @returns The Virtual Corrections of the Matrix Element
*
* Incoming particles should be ordered by ascending z momentum.
* Outgoing particles should be ordered by ascending rapidity.
*
* The all order virtual corrections to LL in the MRK limit is
* given by replacing 1/t in the scattering amplitude according to the
* lipatov ansatz.
*
* cf. second-to-last line of eq. (22) in \cite Andersen:2011hs
* note that indices are off by one, i.e. out[0].p corresponds to p_1
*/
double virtual_corrections(
double mur,
std::array<Particle, 2> const & in,
std::vector<Particle> const & out
) const;
private:
//! \internal cf. last line of eq. (22) in \cite Andersen:2011hs
double omega0(
double alpha_s, double mur,
fastjet::PseudoJet const & q_j, double lambda
) const;
double tree_kin_jets(
std::array<Particle, 2> const & incoming,
std::vector<Particle> partons,
bool check_momenta
) const;
double tree_kin_Higgs(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
double tree_kin_Higgs_first(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
double tree_kin_Higgs_last(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
/**
* \internal
* \brief Higgs inbetween extremal partons.
*
* Note that in the case of unordered emission, the Higgs is *always*
* treated as if in between the extremal (FKL) partons, even if its
* rapidity is outside the extremal parton rapidities
*/
double tree_kin_Higgs_between(
std::array<Particle, 2> const & incoming,
std::vector<Particle> const & outgoing,
bool check_momenta
) const;
double tree_param_partons(
double alpha_s, double mur,
std::vector<Particle> const & partons
) const;
std::vector<int> in_extremal_jet_indices(
std::vector<fastjet::PseudoJet> const & partons
) const;
std::vector<Particle> tag_extremal_jet_partons(
std::array<Particle, 2> const & incoming,
std::vector<Particle> out_partons, bool check_momenta
) const;
double 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;
std::function<double (double)> alpha_s_;
MatrixElementConfig param_;
};
}
diff --git a/src/MatrixElement.cc b/src/MatrixElement.cc
index 637a262..61de326 100644
--- a/src/MatrixElement.cc
+++ b/src/MatrixElement.cc
@@ -1,761 +1,770 @@
#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/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);
+ if(outgoing[1].type != pid::gluon) {
+ assert(incoming.front().type == outgoing[1].type);
+ return tree_kin_Higgs_between(incoming, outgoing, check_momenta);
+ }
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,
+ 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);
+ if(outgoing[outgoing.size()-2].type != pid::gluon) {
+ assert(incoming.back().type == outgoing[outgoing.size()-2].type);
+ return tree_kin_Higgs_between(incoming, outgoing, check_momenta);
+ }
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,
+ 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 == end(partons) && (
+ has_unob_gluon(incoming, outgoing)
+ || partons.back().type != pid::gluon
+ ))
|| first_after_Higgs->rapidity() >= the_Higgs->rapidity()
);
assert(
- (first_after_Higgs == begin(partons) && has_unof_gluon(incoming, outgoing))
+ (first_after_Higgs == begin(partons) && (
+ has_unof_gluon(incoming, outgoing)
+ || partons.front().type != pid::gluon
+ ))
|| (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

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