Rivet analyses
Studies of 2 b-jet + 2 jet production in proton-proton collisions at 7 TeV
Experiment: CMS (LHC)
Inspire ID: 1486238
Status: VALIDATED
Authors: - P. Gunnellini
References: - Expt page: CMS-FSQ-13-010 - CERN-EP-2016-191 - arXiv: 1609.03489 - Phys.Rev. D94 (2016) no.11, 112005
Beams: p+ p+
Beam energies: (3500.0, 3500.0)GeV
Run details: - Hard QCD events with cut at generator level of 15 GeV. Needs 2 b-jets with $\pT > 20$ GeV in |η| < 2.4; 2 jets with $\pT > 20$ GeV in |η| < 4.7
Measurements are presented of the cross section for the production of at least four jets, of which at least two originate from b quarks, in proton-proton collisions. Data collected with the CMS detector at the LHC at a center-of-mass energy of 7 TeV are used, corresponding to an integrated luminosity of 3 inverse picobarns. The cross section is measured as a function of the jet transverse momentum for GeV, and of the jet pseudorapidity for |η| < 2.4 (b jets) and 4.7 (untagged jets). The correlations in azimuthal angle and between the jets are also studied. The η and distributions of the four jets and the correlations between them are well reproduced by event generators that combine perturbative QCD calculations at next-to-leading-order accuracy with contributions from parton showers and multiparton interactions.
Source
code:CMS_2016_I1486238.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/FastJets.hh"
#define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT
#include "Rivet/Projections/InitialQuarks.hh"
namespace Rivet {
/// Studies of 2 b-jet + 2 jet production in proton-proton collisions at 7 TeV
class CMS_2016_I1486238 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2016_I1486238);
/// @name Analysis methods
/// @{
/// Book histograms and initialise projections before the run
void init() {
FastJets akt(FinalState(), JetAlg::ANTIKT, 0.5);
declare(akt, "antikT");
book(_h_Deltaphi_newway, 1,1,1);
book(_h_deltaphiafterlight, 9,1,1);
book(_h_SumPLight, 5,1,1);
book(_h_LeadingBJetpt, 11,1,1);
book(_h_SubleadingBJetpt, 15,1,1);
book(_h_LeadingLightJetpt, 13,1,1);
book(_h_SubleadingLightJetpt, 17,1,1);
book(_h_LeadingBJeteta, 10,1,1);
book(_h_SubleadingBJeteta, 14,1,1);
book(_h_LeadingLightJeteta, 12,1,1);
book(_h_SubleadingLightJeteta, 16,1,1);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
const Jets& jets = apply<JetFinder>(event, "antikT").jetsByPt(Cuts::absrap < 4.7 && Cuts::pT > 20*GeV);
if (jets.size() < 4) vetoEvent;
// Initial quarks
/// @note Quark-level tagging...
Particles bquarks;
for (ConstGenParticlePtr p : HepMCUtils::particles(event.genEvent())) {
if (abs(p->pdg_id()) == PID::BQUARK) bquarks += Particle(p);
}
Jets bjets, ljets;
for (const Jet& j : jets) {
const bool btag = any(bquarks, deltaRLess(j, 0.3));
// for (const Particle& b : bquarks) if (deltaR(j, b) < 0.3) btag = true;
(btag && j.abseta() < 2.4 ? bjets : ljets).push_back(j);
}
// Fill histograms
if (bjets.size() >= 2 && ljets.size() >= 2) {
_h_LeadingBJetpt->fill(bjets[0].pT()/GeV);
_h_SubleadingBJetpt->fill(bjets[1].pT()/GeV);
_h_LeadingLightJetpt->fill(ljets[0].pT()/GeV);
_h_SubleadingLightJetpt->fill(ljets[1].pT()/GeV);
//
_h_LeadingBJeteta->fill(bjets[0].eta());
_h_SubleadingBJeteta->fill(bjets[1].eta());
_h_LeadingLightJeteta->fill(ljets[0].eta());
_h_SubleadingLightJeteta->fill(ljets[1].eta());
const double lightdphi = deltaPhi(ljets[0], ljets[1]);
_h_deltaphiafterlight->fill(lightdphi);
const double vecsumlightjets = sqrt(sqr(ljets[0].px()+ljets[1].px()) + sqr(ljets[0].py()+ljets[1].py())); //< @todo Just (lj0+lj1).pT()? Or use add_quad
const double term2 = vecsumlightjets/(sqrt(sqr(ljets[0].px()) + sqr(ljets[0].py())) + sqrt(sqr(ljets[1].px()) + sqr(ljets[1].py()))); //< @todo lj0.pT() + lj1.pT()? Or add_quad
_h_SumPLight->fill(term2);
const double pxBsyst2 = bjets[0].px()+bjets[1].px(); // @todo (bj0+bj1).px()
const double pyBsyst2 = bjets[0].py()+bjets[1].py(); // @todo (bj0+bj1).py()
const double pxJetssyst2 = ljets[0].px()+ljets[1].px(); // @todo (lj0+lj1).px()
const double pyJetssyst2 = ljets[0].py()+ljets[1].py(); // @todo (lj0+lj1).py()
const double modulusB2 = sqrt(sqr(pxBsyst2)+sqr(pyBsyst2)); //< @todo add_quad
const double modulusJets2 = sqrt(sqr(pxJetssyst2)+sqr(pyJetssyst2)); //< @todo add_quad
const double cosphiBsyst2 = pxBsyst2/modulusB2;
const double cosphiJetssyst2 = pxJetssyst2/modulusJets2;
const double phiBsyst2 = ((pyBsyst2 > 0) ? 1 : -1) * acos(cosphiBsyst2); //< @todo sign(pyBsyst2)
const double phiJetssyst2 = sign(pyJetssyst2) * acos(cosphiJetssyst2);
const double Dphi2 = deltaPhi(phiBsyst2, phiJetssyst2);
_h_Deltaphi_newway->fill(Dphi2);
}
}
/// Normalise histograms etc., after the run
void finalize() {
const double invlumi = crossSection()/picobarn/sumOfWeights();
normalize(_h_SumPLight); normalize(_h_deltaphiafterlight); normalize(_h_Deltaphi_newway);
scale(_h_LeadingLightJetpt, invlumi); scale(_h_SubleadingLightJetpt, invlumi);
scale(_h_LeadingBJetpt, invlumi); scale(_h_SubleadingBJetpt, invlumi);
scale(_h_LeadingLightJeteta, invlumi); scale(_h_SubleadingLightJeteta, invlumi);
scale(_h_LeadingBJeteta, invlumi); scale(_h_SubleadingBJeteta, invlumi);
}
/// @}
private:
/// @name Histograms
/// @{
Histo1DPtr _h_deltaphiafterlight, _h_Deltaphi_newway, _h_SumPLight;
Histo1DPtr _h_LeadingBJetpt, _h_SubleadingBJetpt, _h_LeadingLightJetpt, _h_SubleadingLightJetpt;
Histo1DPtr _h_LeadingBJeteta, _h_SubleadingBJeteta, _h_LeadingLightJeteta, _h_SubleadingLightJeteta;
};
RIVET_DECLARE_PLUGIN(CMS_2016_I1486238);
}