Rivet analyses
title: ATLAS_2015_I1394679
Multijets at 8 TeV
Experiment: ATLAS (LHC)
Inspire ID: 1394679
Status: VALIDATED
Authors: - Sabrina Sacerdoti
References: - Expt page: ATLAS-STDM-2014-14 - arXiv: 1509.07335
Beams: p+ p+
Beam energies: (4000.0, 4000.0)GeV
Run details: - p + p -> j j j j + X
Differential cross sections for the production of at least four jets have been measured in proton-proton collisions at $\sqrt{s}=8$\,TeV at the Large Hadron Collider using the ATLAS detector. The dataset corresponds to an integrated luminosity of 20.3\,fb^{-1}. The cross sections are corrected for detector effects and presented as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables.
Source code:ATLAS_2015_I1394679.cc
```c++ // -- C++ --
include "Rivet/Analysis.hh"
include "Rivet/Projections/FastJets.hh"
include "Rivet/Projections/FinalState.hh"
namespace Rivet {
/// Differential multijet cross-section measurement in different variables class ATLAS_2015_I1394679 : public Analysis { public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2015_I1394679);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections here
const FinalState fs;
declare(fs, "FinalState");
FastJets fj04(fs, JetAlg::ANTIKT, 0.4, JetMuons::ALL, JetInvisibles::DECAY);
declare(fj04, "AntiKt4jets");
// Histograms
book(_h["pt1"], 1, 1, 1);
book(_h["pt2"], 2, 1, 1);
book(_h["pt3"], 3, 1, 1);
book(_h["pt4"], 4, 1, 1);
book(_h["HT"], 5, 1, 1);
book(_h["M4j"], 6, 1, 1);
// Histograms with different pt/m4j cuts
for (size_t i_hist = 0; i_hist < 4; ++i_hist) {
book(_h["M2jratio_" + to_str(i_hist)], 7 + i_hist, 1, 1);
book(_h["dPhiMin2j_" + to_str(i_hist)], 11 + i_hist, 1, 1);
book(_h["dPhiMin3j_" + to_str(i_hist)], 15 + i_hist, 1, 1);
book(_h["dYMin2j_" + to_str(i_hist)], 19 + i_hist, 1, 1);
book(_h["dYMin3j_" + to_str(i_hist)], 23 + i_hist, 1, 1);
book(_h["dYMax2j_" + to_str(i_hist)], 27 + i_hist, 1, 1);
for (size_t ygap = 0; ygap < 4; ++ygap) {
book(_h["sumPtCent_" + to_str(ygap) + to_str(i_hist)], 31 + i_hist + ygap * 4, 1, 1);
}
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
const Jets& alljetskt4 = apply<FastJets>(event, "AntiKt4jets")
.jetsByPt(Cuts::pT > 60 * GeV && Cuts::absrap < 2.8);
// Require 4 jets with rap < 2.8 and passing pT cuts
int nJets = alljetskt4.size();
if (nJets < 4) vetoEvent;
Jets leadingJetskt4 = alljetskt4;
leadingJetskt4.resize(4);
Jet jet1(leadingJetskt4[0]), jet2(leadingJetskt4[1]), jet3(leadingJetskt4[2]), jet4(leadingJetskt4[3]);
if (jet1.pT() < 100 * GeV) vetoEvent;
if (jet4.pT() < 64 * GeV) vetoEvent;
// dR cut
const double dRcut = 0.65;
double drmin = 9999;
for (int ijet = 0; ijet < 4; ++ijet) {
for (int jjet = ijet + 1; jjet < 4; ++jjet) {
double myDR = deltaR(alljetskt4[ijet], alljetskt4[jjet], RAPIDITY);
if (myDR < drmin) drmin = myDR;
}
}
if (drmin < dRcut) vetoEvent;
// Variables for calculation in loops over jets
FourMomentum sum_alljets;
double HT = 0; // scalar sum of pt of 4 leading jets
double Mjj = 99999; // minimum combined mass of 2 jets
double minDphi_ij = 999, minDphi_ijk = 999; // minimum azimuthal distance btw 2 & 3 jets
double maxDrap_ij = -999; // maximum rapidity distance btw 2 jets
double minDrap_ij = 999, minDrap_ijk = 999; // minimum rapidity distance btw 2 & 3 jets
size_t maxY_i = -1, maxY_j = -1;
// Loop over 4 leading jets
for (size_t ij = 0; ij < 4; ++ij) {
Jet& jeti = leadingJetskt4.at(ij);
sum_alljets += jeti.mom();
HT += jeti.pT();
for (size_t jj = 0; jj < 4; ++jj) {
if (ij == jj) continue;
Jet& jetj = leadingJetskt4.at(jj);
const double auxDphi = fabs(deltaPhi(jeti, jetj));
minDphi_ij = std::min(auxDphi, minDphi_ij);
const double auxDrap = fabs(deltaRap(jeti, jetj));
minDrap_ij = std::min(auxDrap, minDrap_ij);
if (auxDrap > maxDrap_ij) {
maxDrap_ij = auxDrap;
maxY_i = ij;
maxY_j = jj;
}
FourMomentum sum_twojets = jeti.mom() + jetj.mom();
Mjj = std::min(Mjj, sum_twojets.mass());
for (size_t kj = 0; kj < 4; ++kj) {
if (kj == ij || kj == jj) continue;
Jet& jetk = leadingJetskt4.at(kj);
const double auxDphi2 = auxDphi + fabs(deltaPhi(jeti, jetk));
minDphi_ijk = std::min(auxDphi2, minDphi_ijk);
const double auxDrap2 = auxDrap + fabs(deltaRap(jeti, jetk));
minDrap_ijk = std::min(auxDrap2, minDrap_ijk);
}
}
} //end loop over 4 leading jets
// Combined mass of 4 leading jets
const double Mjjjj = sum_alljets.mass();
// Sum of central jets pT
double sumpt_twojets_cent = 0; // Scalar sum pt of central jets, with different rapidity gaps
for (size_t ijet = 0; ijet < 4; ++ijet) {
if (ijet == maxY_i || ijet == maxY_j) continue; // these are the forward jets
sumpt_twojets_cent += leadingJetskt4.at(ijet).pT();
}
// Fill histos
// Mass and pT cuts in which the analysis tables are split; values are in GeV and cuts are inclusive
const double m4jcuts[4] = {500, 1000, 1500, 2000};
const double pt1cutA[4] = {100, 400, 700, 1000};
const double pt1cutB[4] = {100, 250, 400, 550};
const double rapGapCut[4] = {1, 2, 3, 4};
_h["pt1"]->fill(jet1.pt());
_h["pt2"]->fill(jet2.pt());
_h["pt3"]->fill(jet3.pt());
_h["pt4"]->fill(jet4.pt());
_h["HT"]->fill(HT);
_h["M4j"]->fill(Mjjjj);
for (size_t i_cut = 0; i_cut < 4; ++i_cut) {
const string icutstr = to_str(i_cut);
if (Mjjjj > m4jcuts[i_cut]) _h["M2jratio_" + icutstr]->fill(Mjj / Mjjjj);
if (jet1.pT() > pt1cutA[i_cut]) {
_h["dPhiMin2j_" + icutstr]->fill(minDphi_ij);
_h["dPhiMin3j_" + icutstr]->fill(minDphi_ijk);
_h["dYMin2j_" + icutstr]->fill(minDrap_ij);
_h["dYMin3j_" + icutstr]->fill(minDrap_ijk);
}
if (jet1.pt() > pt1cutB[i_cut]) {
_h["dYMax2j_" + icutstr]->fill(maxDrap_ij);
for (size_t yy = 0; yy < 4; ++yy) {
if (maxDrap_ij > rapGapCut[yy]) _h["sumPtCent_" + to_str(yy) + icutstr]->fill(sumpt_twojets_cent);
}
}
} //end loop over pt/m4j cuts
}
/// Normalise histograms etc., after the run
void finalize() {
scale(_h, crossSection() / femtobarn / sumOfWeights());
}
/// @}
private:
/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
/// @}
};
RIVET_DECLARE_PLUGIN(ATLAS_2015_I1394679);
} ```