Rivet analyses
Z + jets in pp at 7 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1230812
Status: VALIDATED
Authors: - Katharina Bierwagen - Frank Siegert
References: - Expt page: ATLAS-STDM-2012-04 - arXiv: 1304.7098 - J. High Energy Phys. 07 (2013) 032
Beams: p+ p+
Beam energies: (3500.0, 3500.0)GeV
Run details: - Z+jets, electronic Z-decays (data are a weighted combination of electron/muon).
Measurements of the production of jets of particles in association with a Z boson in pp collisions at $\sqrt{s}$ = 7 TeV are presented, using data corresponding to an integrated luminosity of 4.6/fb collected by the ATLAS experiment at the Large Hadron Collider. Inclusive and differential jet cross sections in Z events, with Z decaying into electron or muon pairs, are measured for jets with transverse momentum pT > 30 GeV and rapidity |y| < 4.4. This Rivet module implements the event selection for the weighted combination of both decay channels to produce the average cross section for a single lepton flavour, and uses the data from that combination (as in the paper plots). In the default mode this is how it will run, assuming mixed electronic and muonic events. If LMODE is set to EL (MU), the plots for the individual decay channels (with a slightly different fiducial phase space) are made.
Source
code:ATLAS_2013_I1230812.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DileptonFinder.hh"
#include "Rivet/Projections/FastJets.hh"
#include "Rivet/Projections/VetoedFinalState.hh"
#include "Rivet/Projections/PromptFinalState.hh"
namespace Rivet {
/// Z + jets in pp at 7 TeV (combined channel / base class)
///
/// @note This base class contains a "mode" variable for combined, e, and mu channel derived classes
class ATLAS_2013_I1230812 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2013_I1230812);
/// Book histograms and initialise projections before the run
void init() {
// Get options from the new option system
_mode = 0;
if ( getOption("LMODE") == "EL" ) _mode = 1;
if ( getOption("LMODE") == "MU" ) _mode = 2;
// Determine the e/mu decay channels used (NB Prompt leptons only).
/// @todo Note that Zs are accepted with any rapidity: the cuts are on the e/mu: is this correct?
Cut pt20 = Cuts::pT >= 20*GeV;
Cut eta_e = _mode? Cuts::abseta < 1.37 || Cuts::absetaIn(1.52, 2.47) : Cuts::abseta < 2.5;
Cut eta_m = _mode? Cuts::abseta < 2.4 : Cuts::abseta < 2.5;
DileptonFinder zfinder_el(91.2*GeV, 0.1, eta_e && pt20 && Cuts::abspid == PID::ELECTRON, Cuts::massIn(66*GeV, 116*GeV));
DileptonFinder zfinder_mu(91.2*GeV, 0.1, eta_m && pt20 && Cuts::abspid == PID::MUON, Cuts::massIn(66*GeV, 116*GeV));
declare(zfinder_el, "zfinder_el");
declare(zfinder_mu, "zfinder_mu");
// Define veto FS in order to prevent Z-decay products entering the jet algorithm
VetoedFinalState had_fs;
had_fs.addVetoOnThisFinalState(getProjection<DileptonFinder>("zfinder_el"));
had_fs.addVetoOnThisFinalState(getProjection<DileptonFinder>("zfinder_mu"));
FastJets jets(had_fs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::ALL);
declare(jets, "jets");
book(_h_njet_incl , 1, 1, _mode+1);
book(_h_njet_incl_ratio , 2, 1, _mode+1);
book(_h_njet_excl , 3, 1, _mode+1);
book(_h_njet_excl_ratio , 4, 1, _mode+1);
book(_h_njet_excl_pt150 , 5, 1, _mode+1);
book(_h_njet_excl_pt150_ratio , 6, 1, _mode+1);
book(_h_njet_excl_vbf , 7, 1, _mode+1);
book(_h_njet_excl_vbf_ratio , 8, 1, _mode+1);
book(_h_ptlead , 9, 1, _mode+1);
book(_h_ptseclead , 10, 1, _mode+1);
book(_h_ptthirdlead , 11, 1, _mode+1);
book(_h_ptfourthlead , 12, 1, _mode+1);
book(_h_ptlead_excl , 13, 1, _mode+1);
book(_h_pt_ratio , 14, 1, _mode+1);
book(_h_pt_z , 15, 1, _mode+1);
book(_h_pt_z_excl , 16, 1, _mode+1);
book(_h_ylead , 17, 1, _mode+1);
book(_h_yseclead , 18, 1, _mode+1);
book(_h_ythirdlead , 19, 1, _mode+1);
book(_h_yfourthlead , 20, 1, _mode+1);
book(_h_deltay , 21, 1, _mode+1);
book(_h_mass , 22, 1, _mode+1);
book(_h_deltaphi , 23, 1, _mode+1);
book(_h_deltaR , 24, 1, _mode+1);
book(_h_ptthirdlead_vbf , 25, 1, _mode+1);
book(_h_ythirdlead_vbf , 26, 1, _mode+1);
book(_h_ht , 27, 1, _mode+1);
book(_h_st , 28, 1, _mode+1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
FourMomentum z, lp, lm;
const DileptonFinder& zfinder_el = apply<DileptonFinder>(event, "zfinder_el");
const DileptonFinder& zfinder_mu = apply<DileptonFinder>(event, "zfinder_mu");
bool e_ok = zfinder_el.constituents().size() == 2 && zfinder_mu.constituents().size() == 0;
bool m_ok = zfinder_el.constituents().size() == 0 && zfinder_mu.constituents().size() == 2;
if (_mode == 0 && !e_ok && !m_ok) vetoEvent;
if (_mode == 1 && !e_ok) vetoEvent;
if (_mode == 2 && !m_ok) vetoEvent;
if (zfinder_el.constituents().size() == 2) {
z = zfinder_el.boson().momentum();
lp = zfinder_el.constituents()[0].momentum();
lm = zfinder_el.constituents()[1].momentum();
}
else if (zfinder_mu.constituents().size() == 2) {
z = zfinder_mu.boson().momentum();
lp = zfinder_mu.constituents()[0].momentum();
lm = zfinder_mu.constituents()[1].momentum();
}
else vetoEvent;
if (deltaR(lp, lm) < 0.2) vetoEvent;
Jets jets = apply<FastJets>(event, "jets").jetsByPt(Cuts::pT > 30*GeV && Cuts::absrap < 4.4);
idiscard(jets, deltaRLess(lp, 0.5));
idiscard(jets, deltaRLess(lm, 0.5));
// Fill jet multiplicities
for (size_t ijet = 0; ijet <= jets.size(); ++ijet) {
_h_njet_incl->fill(ijet);
}
_h_njet_excl->fill(jets.size());
// Require at least one jet
if (jets.size() >= 1) {
// Leading jet histos
const double ptlead = jets[0].pT()/GeV;
const double yabslead = fabs(jets[0].rapidity());
const double ptz = z.pT()/GeV;
_h_ptlead->fill(ptlead);
_h_ylead ->fill(yabslead);
_h_pt_z ->fill(ptz);
// Fill jet multiplicities
if (ptlead > 150) _h_njet_excl_pt150->fill(jets.size());
// Loop over selected jets, fill inclusive distributions
double st = 0;
double ht = lp.pT()/GeV + lm.pT()/GeV;
for (size_t ijet = 0; ijet < jets.size(); ++ijet) {
ht += jets[ijet].pT()/GeV;
st += jets[ijet].pT()/GeV;
}
_h_ht->fill(ht);
_h_st->fill(st);
// Require exactly one jet
if (jets.size() == 1) {
_h_ptlead_excl->fill(ptlead);
_h_pt_z_excl ->fill(ptz);
}
}
// Require at least two jets
if (jets.size() >= 2) {
// Second jet histos
const double ptlead = jets[0].pT()/GeV;
const double pt2ndlead = jets[1].pT()/GeV;
const double ptratio = pt2ndlead/ptlead;
const double yabs2ndlead = fabs(jets[1].rapidity());
_h_ptseclead->fill(pt2ndlead);
_h_yseclead->fill( yabs2ndlead);
_h_pt_ratio->fill( ptratio);
// Dijet histos
const double deltaphi = fabs(deltaPhi(jets[1], jets[0]));
const double deltarap = fabs(jets[0].rapidity() - jets[1].rapidity()) ;
const double deltar = fabs(deltaR(jets[0], jets[1], RAPIDITY));
const double mass = (jets[0].momentum() + jets[1].momentum()).mass()/GeV;
_h_mass->fill( mass);
_h_deltay->fill( deltarap);
_h_deltaphi->fill(deltaphi);
_h_deltaR->fill( deltar);
if (mass > 350 && deltarap > 3) _h_njet_excl_vbf->fill(jets.size());
}
// Require at least three jets
if (jets.size() >= 3) {
// Third jet histos
const double pt3rdlead = jets[2].pT()/GeV;
const double yabs3rdlead = fabs(jets[2].rapidity());
_h_ptthirdlead->fill(pt3rdlead);
_h_ythirdlead->fill( yabs3rdlead);
//Histos after VBF preselection
const double deltarap = fabs(jets[0].rapidity() - jets[1].rapidity()) ;
const double mass = (jets[0].momentum() + jets[1].momentum()).mass();
if (mass > 350 && deltarap > 3) {
_h_ptthirdlead_vbf->fill(pt3rdlead);
_h_ythirdlead_vbf->fill( yabs3rdlead);
}
}
// Require at least four jets
if (jets.size() >= 4) {
// Fourth jet histos
const double pt4thlead = jets[3].pT()/GeV;
const double yabs4thlead = fabs(jets[3].rapidity());
_h_ptfourthlead->fill(pt4thlead);
_h_yfourthlead->fill( yabs4thlead);
}
}
/// @name Ratio calculator util functions
/// @{
/// Calculate the efficiency error, being careful about div-by-zero
double err_incl(const YODA::Dbn1D& M, const YODA::Dbn1D& N, bool hasWeights) {
double r = safediv(M.sumW(), N.sumW());
if (hasWeights) { // use F. James's approximation for weighted events
return sqrt( safediv((1 - 2 * r) * M.sumW2() + r * r * N.sumW2(), N.sumW() * N.sumW()) );
}
return sqrt( safediv(r * (1 - r), N.sumW()) );
}
/// Calculate the ratio error, being careful about div-by-zero
double err_excl(const YODA::Dbn1D& A, const YODA::Dbn1D& B) {
double r = safediv(A.sumW(), B.sumW());
double dAsquared = safediv(A.sumW2(), A.sumW() * A.sumW()); // squared relative error of A
double dBsquared = safediv(B.sumW2(), B.sumW() * B.sumW()); // squared relative error of B
return r * sqrt(dAsquared + dBsquared);
}
/// @}
void finalize() {
const bool hasWeights = _h_njet_incl->effNumEntries() != _h_njet_incl->numEntries();
for (size_t i = 0; i < 6; ++i) {
_h_njet_incl_ratio->bin(i+1).set(safediv(_h_njet_incl->bin(i + 2).sumW(), _h_njet_incl->bin(i+1).sumW()),
err_incl(_h_njet_incl->bin(i + 2).raw(), _h_njet_incl->bin(i+1).raw(), hasWeights));
_h_njet_excl_ratio->bin(i+1).set(safediv(_h_njet_excl->bin(i + 2).sumW(), _h_njet_excl->bin(i+1).sumW()),
err_excl(_h_njet_excl->bin(i + 2).raw(), _h_njet_excl->bin(i+1).raw()));
if (i >= 1) {
_h_njet_excl_pt150_ratio->bin(i).set(safediv(_h_njet_excl_pt150->bin(i+1).sumW(), _h_njet_excl_pt150->bin(i).sumW()),
err_excl(_h_njet_excl_pt150->bin(i+1).raw(), _h_njet_excl_pt150->bin(i).raw()));
if (i >= 2) {
_h_njet_excl_vbf_ratio->bin(i - 1).set(safediv(_h_njet_excl_vbf->bin(i+1).sumW(), _h_njet_excl_vbf->bin(i).sumW()),
err_excl(_h_njet_excl_vbf->bin(i+1).raw(), _h_njet_excl_vbf->bin(i).raw()));
}
}
}
const double sf = _mode? 1.0 : 0.5;
const double xs = sf * crossSectionPerEvent()/picobarn;
scale(_h_njet_incl, xs); scale(_h_njet_excl, xs); scale(_h_njet_excl_pt150, xs);
scale(_h_njet_excl_vbf, xs); scale(_h_ptlead, xs); scale(_h_ptseclead, xs);
scale(_h_ptthirdlead, xs); scale(_h_ptfourthlead, xs); scale(_h_ptlead_excl, xs);
scale(_h_pt_ratio, xs); scale(_h_pt_z, xs); scale(_h_pt_z_excl, xs);
scale(_h_ylead, xs); scale(_h_yseclead, xs); scale(_h_ythirdlead, xs);
scale(_h_yfourthlead, xs); scale(_h_deltay, xs); scale(_h_mass, xs);
scale(_h_deltaphi, xs); scale(_h_deltaR, xs); scale(_h_ptthirdlead_vbf, xs);
scale(_h_ythirdlead_vbf, xs); scale(_h_ht, xs); scale(_h_st, xs);
}
/// @}
protected:
size_t _mode;
private:
Estimate1DPtr _h_njet_incl_ratio;
Estimate1DPtr _h_njet_excl_ratio;
Estimate1DPtr _h_njet_excl_pt150_ratio;
Estimate1DPtr _h_njet_excl_vbf_ratio;
Histo1DPtr _h_njet_incl;
Histo1DPtr _h_njet_excl;
Histo1DPtr _h_njet_excl_pt150;
Histo1DPtr _h_njet_excl_vbf;
Histo1DPtr _h_ptlead;
Histo1DPtr _h_ptseclead;
Histo1DPtr _h_ptthirdlead;
Histo1DPtr _h_ptfourthlead;
Histo1DPtr _h_ptlead_excl;
Histo1DPtr _h_pt_ratio;
Histo1DPtr _h_pt_z;
Histo1DPtr _h_pt_z_excl;
Histo1DPtr _h_ylead;
Histo1DPtr _h_yseclead;
Histo1DPtr _h_ythirdlead;
Histo1DPtr _h_yfourthlead;
Histo1DPtr _h_deltay;
Histo1DPtr _h_mass;
Histo1DPtr _h_deltaphi;
Histo1DPtr _h_deltaR;
Histo1DPtr _h_ptthirdlead_vbf;
Histo1DPtr _h_ythirdlead_vbf;
Histo1DPtr _h_ht;
Histo1DPtr _h_st;
};
RIVET_DECLARE_PLUGIN(ATLAS_2013_I1230812);
}