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## Rivet analyses reference

### CMS_2013_I1258128

Rapidity distributions in exclusive $Z$ + jet and $\gamma$ + jet events in $pp$ collisions at $\sqrt{s} = 7$ TeV
Experiment: CMS (LHC)
Inspire ID: 1258128
Status: VALIDATED
Authors:
• Steve Linn
• Shin-Shan Eiko Yu
• Anil Sing Pratap
• Lovedeep Kaur Saini
• Kittikul Kovitanggoon
• Luis Lebolo
• Vanessa Gaultney Werner
• Yun-Ju Lu
• Syue-Wei Li
• Yu-Hsiang Chang
• Sung-Won Lee
• Pete E.C. Markowitz
• Darko Mekterovic
• Jorge Rodriguez
• Bhawan Uppal
References:
• arXiv: 1310.3082
• https://twiki.cern.ch/twiki/bin/view/CMSPublic/PhysicsResultsSMP12004
• Submitted to Phys. Rev. Lett
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
• Run MC generators with $Z$ decaying to leptonic modes + jets and photon + jets at 7 TeV centre-of-mass energy.

Rapidity distributions are presented for events containing either a $Z$ boson or a photon in association with a single jet in proton-proton collisions produced at the CERN LHC. The data, collected with the CMS detector at $\sqrt{s} = 7$ TeV, correspond to an integrated luminosity of 5.0/fb. The individual rapidity distributions of the boson and the jet are consistent within 5\% with expectations from perturbative QCD. However, QCD predictions for the sum and the difference in rapidities of the two final-state objects show significant discrepancies with CMS data. In particular, next-to-leading-order QCD calculations, and two Monte Carlo event generators using different methods to merge matrix-element partons with evolved parton showers, appear inconsistent with the data as well as with each other.

Source code: CMS_2013_I1258128.cc
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 #include "Rivet/Analysis.hh" #include "Rivet/Tools/BinnedHistogram.hh" #include "Rivet/Projections/FinalState.hh" #include "Rivet/Projections/FastJets.hh" #include "Rivet/Projections/ZFinder.hh" #include "Rivet/Projections/Thrust.hh" #include "Rivet/Projections/LeadingParticlesFinalState.hh" namespace Rivet { /// CMS Z rapidity measurement class CMS_2013_I1258128 : public Analysis { public: // Constructor DEFAULT_RIVET_ANALYSIS_CTOR(CMS_2013_I1258128); void init() { // Full final state const FinalState fs(Cuts::abseta < 5); declare(fs, "FS"); // Z finders for electrons and muons Cut cuts = Cuts::abseta < 2.1 && Cuts::pT > 20*GeV; const ZFinder zfe(fs, cuts, PID::ELECTRON, 76*GeV, 106*GeV); const ZFinder zfm(fs, cuts, PID::MUON, 76*GeV, 106*GeV); declare(zfe, "ZFE"); declare(zfm, "ZFM"); // Try to get the leading photon LeadingParticlesFinalState photonfs(FinalState(-2.5, 2.5, 40.0*GeV)); photonfs.addParticleId(PID::PHOTON); declare(photonfs, "LeadingPhoton"); // Jets const FastJets jets(fs, FastJets::ANTIKT, 0.5); declare(jets, "JETS"); // Histograms _hist1YZ = bookHisto1D(1, 1, 1); _hist1YJet = bookHisto1D(2, 1, 1); _hist1YSum = bookHisto1D(3, 1, 1); _hist1YDif = bookHisto1D(4, 1, 1); _hist2YPhoton = bookHisto1D(5, 1, 1); _hist2YJet = bookHisto1D(6, 1, 1); _hist2YSum = bookHisto1D(7, 1, 1); _hist2YDif = bookHisto1D(8, 1, 1); } void makeZCut(const Event& event) { // Apply the Z finders and veto if no Z found const ZFinder& zfe = apply(event, "ZFE"); const ZFinder& zfm = apply(event, "ZFM"); if (zfe.empty() && zfm.empty()) vetoEvent; // Choose the Z candidate const ParticleVector& z = (!zfm.empty()) ? zfm.bosons() : zfe.bosons(); const ParticleVector& clusteredConstituents = (!zfm.empty()) ? zfm.constituents() : zfe.constituents(); // Insist that the Z is in a high-pT (boosted) regime if (z[0].pT() < 40*GeV) return; // Build the jets const FastJets& jetfs = apply(event, "JETS"); Jets jets = jetfs.jetsByPt(Cuts::pT > 30*GeV && Cuts::abseta < 2.4); if (jets.empty()) return; // Clean the jets against the lepton candidates with a DeltaR cut of 0.5 vector cleanedJets; foreach (const Jet& j, jets) { bool isolated = true; foreach (const Particle& p, clusteredConstituents) { if (deltaR(p, j) < 0.5) { isolated = false; break; } } if (isolated) cleanedJets.push_back(&j); } // Require exactly 1 isolated jet if (cleanedJets.size() != 1) return; // Fill histos const double weight = event.weight(); const double yz = z[0].rapidity(); const double yjet = cleanedJets[0]->momentum().rapidity(); _hist1YZ->fill(fabs(yz), weight); _hist1YJet->fill(fabs(yjet), weight); _hist1YSum->fill(0.5*fabs(yz + yjet), weight); _hist1YDif->fill(0.5*fabs(yz - yjet), weight); } void makePhotonCut(const Event& event) { // Get the photon const FinalState& photonfs = apply(event, "LeadingPhoton"); if (photonfs.particles().size() < 1) return; const Particle& photon = photonfs.particles().front(); if (photon.pT() < 40*GeV) return; if (fabs(photon.eta()) > 1.4442 ) return; // Build the jets const FastJets& jetfs = apply(event, "JETS"); Jets jets = jetfs.jetsByPt(Cuts::pT > 30*GeV && Cuts::abseta < 2.4); if (jets.empty()) return; // Clean the jets against the photon candidate with a DeltaR cut of 0.5 vector cleanedJets; foreach (const Jet& j, jets) if (deltaR(photon, j) > 0.5) cleanedJets.push_back(&j); // Require exactly 1 jet if (cleanedJets.size() != 1) return; // Fill histos const double weight = event.weight(); const double ypho = photon.rapidity(); const double yjet = cleanedJets[0]->momentum().rapidity(); _hist2YPhoton->fill(fabs(ypho), weight); _hist2YJet->fill(fabs(yjet), weight); _hist2YSum->fill(0.5*fabs(ypho + yjet), weight); _hist2YDif->fill(0.5*fabs(ypho - yjet), weight); } void analyze(const Event& event) { makeZCut(event); makePhotonCut(event); } void finalize() { normalizeByContents(_hist1YZ); normalizeByContents(_hist1YJet); normalizeByContents(_hist1YSum); normalizeByContents(_hist1YDif); normalizeByContents(_hist2YPhoton); normalizeByContents(_hist2YJet); normalizeByContents(_hist2YSum); normalizeByContents(_hist2YDif); } // The CMS normalization in this analysis is that the sum over bin contents // is equal to 1. This function normalizes to area = area*bin_width. / // @note This is a strange definition... why? void normalizeByContents(Histo1DPtr h) { normalize(h, h->bin(0).xWidth()); } private: Histo1DPtr _hist1YZ, _hist1YJet, _hist1YSum, _hist1YDif; Histo1DPtr _hist2YPhoton, _hist2YJet, _hist2YSum, _hist2YDif; }; // Plugin system hook DECLARE_RIVET_PLUGIN(CMS_2013_I1258128); }