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| #include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/ChargedLeptons.hh"
#include "Rivet/Projections/MissingMomentum.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/AnalysisLoader.hh"
namespace Rivet {
class MC_TTBAR : public Analysis {
public:
/// Minimal constructor
RIVET_DEFAULT_ANALYSIS_CTOR(MC_TTBAR);
/// @name Analysis methods
//@{
/// Set up projections and book histograms
void init() {
_mode = 1; string pre = "onelep_"; // default is single-lepton decay mode
if ( getOption("TTMODE") == "ALLHAD" ) { _mode = 0; pre = "allhad_"; }
if ( getOption("TTMODE") == "ONELEP" ) { _mode = 1; pre = "onelep_"; }
if ( getOption("TTMODE") == "TWOLEP" ) { _mode = 2; pre = "twolep_"; }
if ( getOption("TTMODE") == "ANYLEP" ) { _mode = 3; pre = "anylep_"; }
// A FinalState is used to select particles within |eta| < 4.2 and with pT
// > 30 GeV, out of which the ChargedLeptons projection picks only the
// electrons and muons, to be accessed later as "LFS".
ChargedLeptons lfs(FinalState(Cuts::abseta < 4.2 && Cuts::pT > 30*GeV));
declare(lfs, "LFS");
// A second FinalState is used to select all particles in |eta| < 4.2,
// with no pT cut. This is used to construct jets and measure missing
// transverse energy.
VetoedFinalState fs(FinalState(Cuts::abseta < 4.2));
fs.addVetoOnThisFinalState(lfs);
declare(FastJets(fs, FastJets::ANTIKT, 0.6), "Jets");
declare(MissingMomentum(fs), "MissingET");
// Booking of histograms
book(_h["njets"], pre + "jet_mult", 11, -0.5, 10.5);
//
book(_h["jet_1_pT"], pre + "jet_1_pT", logspace(50, 20.0, 500.0));
book(_h["jet_2_pT"], pre + "jet_2_pT", logspace(50, 20.0, 400.0));
book(_h["jet_3_pT"], pre + "jet_3_pT", logspace(50, 20.0, 300.0));
book(_h["jet_4_pT"], pre + "jet_4_pT", logspace(50, 20.0, 200.0));
book(_h["jet_HT"], pre + "jet_HT", logspace(50, 100.0, 2000.0));
//
book(_h["bjet_1_pT"], pre + "jetb_1_pT", logspace(50, 20.0, 400.0));
book(_h["bjet_2_pT"], pre + "jetb_2_pT", logspace(50, 20.0, 300.0));
//
book(_h["ljet_1_pT"], pre + "jetl_1_pT", logspace(50, 20.0, 400.0));
book(_h["ljet_2_pT"], pre + "jetl_2_pT", logspace(50, 20.0, 300.0));
//
if (_mode != 2) book(_h["tt_mass"], pre + "tt_mass", 200, 300.0, 700.0);
//
if (_mode < 2) { // these rely on a hadronic W being part of the ttbar decay
book(_h["W_mass"], pre + "W_mass", 75, 30, 180);
book(_h["t_mass"], pre + "t_mass", 150, 130, 430);
book(_h["t_mass_W_cut"], pre + "t_mass_W_cut", 150, 130, 430);
book(_h["jetb_1_W_dR"], pre + "jetb_1_W_dR", 20, 0.0, 7.0);
book(_h["jetb_1_W_deta"], pre + "jetb_1_W_deta", 20, 0.0, 7.0);
book(_h["jetb_1_W_dphi"], pre + "jetb_1_W_dphi", 20, 0.0, M_PI);
}
//
book(_h["jetb_1_jetb_2_dR"], pre + "jetb_1_jetb_2_dR", 20, 0.0, 7.0);
book(_h["jetb_1_jetb_2_deta"], pre + "jetb_1_jetb_2_deta", 20, 0.0, 7.0);
book(_h["jetb_1_jetb_2_dphi"], pre + "jetb_1_jetb_2_dphi", 20, 0.0, M_PI);
book(_h["jetb_1_jetl_1_dR"], pre + "jetb_1_jetl_1_dR", 20, 0.0, 7.0);
book(_h["jetb_1_jetl_1_deta"], pre + "jetb_1_jetl_1_deta", 20, 0.0, 7.0);
book(_h["jetb_1_jetl_1_dphi"], pre + "jetb_1_jetl_1_dphi", 20, 0.0, M_PI);
book(_h["jetl_1_jetl_2_dR"], pre + "jetl_1_jetl_2_dR", 20, 0.0, 7.0);
book(_h["jetl_1_jetl_2_deta"], pre + "jetl_1_jetl_2_deta", 20, 0.0, 7.0);
book(_h["jetl_1_jetl_2_dphi"], pre + "jetl_1_jetl_2_dphi", 20, 0.0, M_PI);
if (_mode > 0) { // these rely on at least one leptonic decay mode
book(_h["jetb_1_l_dR"], pre + "jetb_1_l_dR", 20, 0.0, 7.0);
book(_h["jetb_1_l_deta"], pre + "jetb_1_l_deta", 20, 0.0, 7.0);
book(_h["jetb_1_l_dphi"], pre + "jetb_1_l_dphi", 20, 0.0, M_PI);
book(_h["jetb_1_l_mass"], pre + "jetb_1_l_mass", 40, 0.0, 500.0);
if (_mode > 1) {
book(_h["jetb_1_l2_dR"], pre + "jetb_1_l2_dR", 20, 0.0, 7.0);
book(_h["jetb_1_l2_deta"], pre + "jetb_1_l2_deta", 20, 0.0, 7.0);
book(_h["jetb_1_l2_dphi"], pre + "jetb_1_l2_dphi", 20, 0.0, M_PI);
book(_h["jetb_1_l2_mass"], pre + "jetb_1_l2_mass", 40, 0.0, 500.0);
}
}
}
void analyze(const Event& event) {
const double weight = 1.0;
// Use the "LFS" projection to require at least one hard charged
// lepton. This is an experimental signature for the leptonically decaying
// W. This helps to reduce pure QCD backgrounds.
const ChargedLeptons& lfs = apply<ChargedLeptons>(event, "LFS");
MSG_DEBUG("Charged lepton multiplicity = " << lfs.chargedLeptons().size());
for (const Particle& lepton : lfs.chargedLeptons()) {
MSG_DEBUG("Lepton pT = " << lepton.pT());
}
size_t nLeps = lfs.chargedLeptons().size();
bool leptonMultiFail = _mode == 3 && nLeps == 0; // non-all-hadronic
leptonMultiFail |= _mode == 2 && nLeps != 2; // dilepton
leptonMultiFail |= _mode == 1 && nLeps != 1; // single lepton
leptonMultiFail |= _mode == 0 && nLeps != 0; // all-hadronic
if (leptonMultiFail) {
MSG_DEBUG("Event failed lepton multiplicity cut");
vetoEvent;
}
// Use a missing ET cut to bias toward events with a hard neutrino from
// the leptonically decaying W. This helps to reduce pure QCD backgrounds.
// not applied in all-hadronic mode
const Vector3& met = apply<MissingMomentum>(event, "MissingET").vectorMissingPt();
MSG_DEBUG("Vector pT = " << met.mod() << " GeV");
if (_mode > 0 && met.mod() < 30*GeV) {
MSG_DEBUG("Event failed missing ET cut");
vetoEvent;
}
// Use the "Jets" projection to check how many jets with pT > 30 GeV there are
// remove jets overlapping with any lepton (dR < 0.3)
// cut on jet multiplicity depending on ttbar decay mode
const FastJets& jetpro = apply<FastJets>(event, "Jets");
const Jets jets = discardIfAnyDeltaRLess(jetpro.jetsByPt(30*GeV), lfs.chargedLeptons(), 0.3);
if ( _mode == 0 && jets.size() < 6) vetoEvent; // all-hadronic
else if (_mode == 1 && jets.size() < 4) vetoEvent; // single lepton
else if (_mode == 2 && jets.size() < 2) vetoEvent; // dilepton
else if (_mode == 3 && nLeps == 1 && jets.size() < 4) vetoEvent; // non-allhadronic
else if (_mode == 3 && nLeps == 2 && jets.size() < 2) vetoEvent;
MSG_DEBUG("Event failed jet multiplicity cut");
// Fill histograms for inclusive jet kinematics
_h["njets"]->fill(jets.size(), weight);
if (jets.size() > 0) _h["jet_1_pT"]->fill(jets[0].pT()/GeV, weight);
if (jets.size() > 1) _h["jet_2_pT"]->fill(jets[1].pT()/GeV, weight);
if (jets.size() > 2) _h["jet_3_pT"]->fill(jets[2].pT()/GeV, weight);
if (jets.size() > 3) _h["jet_4_pT"]->fill(jets[3].pT()/GeV, weight);
double ht = 0.0;
for (const Jet& j : jets) { ht += j.pT(); }
_h["jet_HT"]->fill(ht/GeV, weight);
// Sort the jets into b-jets and light jets. We expect one hard b-jet from
// each top decay, so our 4 hardest jets should include two b-jets. The
// Jet::bTagged() method is equivalent to perfect experimental
// b-tagging, in a generator-independent way.
Jets bjets, ljets;
for (const Jet& jet : jets) {
if (jet.bTagged()) bjets += jet;
else ljets += jet;
}
MSG_DEBUG("Number of b-jets = " << bjets.size());
MSG_DEBUG("Number of l-jets = " << ljets.size());
if (bjets.size() != 2) {
MSG_DEBUG("Event failed post-lepton-isolation b-tagging cut");
vetoEvent;
}
if (_mode == 0 && ljets.size() < 4) vetoEvent;
else if (_mode == 1 && ljets.size() < 2) vetoEvent;
else if (_mode == 3 && nLeps == 1 && ljets.size() < 2) vetoEvent;
// Plot the pTs of the identified jets.
_h["bjet_1_pT"]->fill(bjets[0].pT(), weight);
_h["bjet_2_pT"]->fill(bjets[1].pT(), weight);
// need to check size to cater for dileptonic mode
if (ljets.size() > 0) _h["ljet_1_pT"]->fill(ljets[0].pT(), weight);
if (ljets.size() > 1) _h["ljet_2_pT"]->fill(ljets[1].pT(), weight);
// Try to reconstruct ttbar pair (doesn't really work in the dileptonic mode)
FourMomentum ttpair = bjets[0].mom() + bjets[1].mom();
if (_mode == 0) {
ttpair += ljets[0].mom() + ljets[1].mom() + ljets[2].mom() + ljets[3].mom();
}
else if (nLeps < 2) {
ttpair += ljets[0].mom() + ljets[1].mom();
const FourMomentum lep = lfs.chargedLeptons()[0].mom();
double pz = findZcomponent(lep, met);
FourMomentum neutrino(sqrt(sqr(met.x()) + sqr(met.y()) + sqr(pz)), met.x(), met.y(), pz);
ttpair += lep + neutrino;
}
if (nLeps < 2) _h["tt_mass"]->fill(ttpair.mass()/GeV, weight);
if (_mode < 2) {
// Construct the hadronically decaying W momentum 4-vector from pairs of
// non-b-tagged jets. The pair which best matches the W mass is used. We start
// with an always terrible 4-vector estimate which should always be "beaten" by
// a real jet pair.
FourMomentum W(10*(sqrtS()>0.?sqrtS():14000.), 0, 0, 0);
for (size_t i = 0; i < ljets.size()-1; ++i) {
for (size_t j = i + 1; j < ljets.size(); ++j) {
const FourMomentum Wcand = ljets[i].momentum() + ljets[j].momentum();
MSG_TRACE(i << "," << j << ": candidate W mass = " << Wcand.mass()/GeV
<< " GeV, vs. incumbent candidate with " << W.mass()/GeV << " GeV");
if (fabs(Wcand.mass() - 80.4*GeV) < fabs(W.mass() - 80.4*GeV)) {
W = Wcand;
}
}
}
MSG_DEBUG("Candidate W mass = " << W.mass() << " GeV");
// There are two b-jets with which this can be combined to make the
// hadronically decaying top, one of which is correct and the other is
// not... but we have no way to identify which is which, so we construct
// both possible top momenta and fill the histograms with both.
const FourMomentum t1 = W + bjets[0].momentum();
const FourMomentum t2 = W + bjets[1].momentum();
_h["W_mass"]->fill(W.mass(), weight);
_h["t_mass"]->fill(t1.mass(), weight);
_h["t_mass"]->fill(t2.mass(), weight);
// Placing a cut on the well-known W mass helps to reduce backgrounds
// only done for all-hadronic and semileptonic mode (since W is hadronic)
if (!inRange(W.mass()/GeV, 75.0, 85.0)) vetoEvent;
MSG_DEBUG("W found with mass " << W.mass()/GeV << " GeV");
_h["t_mass_W_cut"]->fill(t1.mass(), weight);
_h["t_mass_W_cut"]->fill(t2.mass(), weight);
_h["jetb_1_W_dR"]->fill(deltaR(bjets[0].momentum(), W),weight);
_h["jetb_1_W_deta"]->fill(fabs(bjets[0].eta()-W.eta()),weight);
_h["jetb_1_W_dphi"]->fill(deltaPhi(bjets[0].momentum(),W),weight);
}
_h["jetb_1_jetb_2_dR"]->fill(deltaR(bjets[0].momentum(), bjets[1].momentum()),weight);
_h["jetb_1_jetb_2_deta"]->fill(fabs(bjets[0].eta()-bjets[1].eta()),weight);
_h["jetb_1_jetb_2_dphi"]->fill(deltaPhi(bjets[0].momentum(),bjets[1].momentum()),weight);
if (ljets.size() > 0) {
_h["jetb_1_jetl_1_dR"]->fill(deltaR(bjets[0].momentum(), ljets[0].momentum()),weight);
_h["jetb_1_jetl_1_deta"]->fill(fabs(bjets[0].eta()-ljets[0].eta()),weight);
_h["jetb_1_jetl_1_dphi"]->fill(deltaPhi(bjets[0].momentum(),ljets[0].momentum()),weight);
if (ljets.size() > 1) {
_h["jetl_1_jetl_2_dR"]->fill(deltaR(ljets[0].momentum(), ljets[1].momentum()),weight);
_h["jetl_1_jetl_2_deta"]->fill(fabs(ljets[0].eta()-ljets[1].eta()),weight);
_h["jetl_1_jetl_2_dphi"]->fill(deltaPhi(ljets[0].momentum(),ljets[1].momentum()),weight);
}
}
// lepton-centric plots
if (_mode > 0) {
FourMomentum l=lfs.chargedLeptons()[0].momentum();
_h["jetb_1_l_dR"]->fill(deltaR(bjets[0].momentum(), l),weight);
_h["jetb_1_l_deta"]->fill(fabs(bjets[0].eta()-l.eta()),weight);
_h["jetb_1_l_dphi"]->fill(deltaPhi(bjets[0].momentum(),l),weight);
_h["jetb_1_l_mass"]->fill(FourMomentum(bjets[0].momentum()+l).mass(), weight);
if (nLeps > 1) {
FourMomentum l=lfs.chargedLeptons()[1].momentum();
_h["jetb_1_l2_dR"]->fill(deltaR(bjets[0].momentum(), l),weight);
_h["jetb_1_l2_deta"]->fill(fabs(bjets[0].eta()-l.eta()),weight);
_h["jetb_1_l2_dphi"]->fill(deltaPhi(bjets[0].momentum(),l),weight);
_h["jetb_1_l2_mass"]->fill(FourMomentum(bjets[0].momentum()+l).mass(), weight);
}
}
}
double findZcomponent(const FourMomentum& lepton, const Vector3& met) const {
// estimate z-component of momentum given lepton 4-vector and MET 3-vector
double pz_estimate;
double m_W = 80.399*GeV;
double k = (( sqr( m_W ) - sqr( lepton.mass() ) ) / 2 ) + (lepton.px() * met.x() + lepton.py() * met.y());
double a = sqr ( lepton.E() )- sqr ( lepton.pz() );
double b = -2*k*lepton.pz();
double c = sqr( lepton.E() ) * sqr( met.perp() ) - sqr( k );
double discriminant = sqr(b) - 4 * a * c;
double quad[2] = { (- b - sqrt(discriminant)) / (2 * a), (- b + sqrt(discriminant)) / (2 * a) }; //two possible quadratic solns
if (discriminant < 0) pz_estimate = - b / (2 * a); //if the discriminant is negative
else { //if the discriminant is greater than or equal to zero, take the soln with smallest absolute value
double absquad[2];
for (int n=0; n<2; ++n) absquad[n] = fabs(quad[n]);
if (absquad[0] < absquad[1]) pz_estimate = quad[0];
else pz_estimate = quad[1];
}
return pz_estimate;
}
void finalize() {
const double sf = crossSection() / sumOfWeights();
for (auto hist : _h) { scale(hist.second, sf); }
}
//@}
protected:
size_t _mode;
private:
// @name Histogram data members
//@{
map<string, Histo1DPtr> _h;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(MC_TTBAR);
}
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