Rivet analyses
Underlying event measurement with leading jets at $\sqrt{s} = 2.76$~
Experiment: CMS (LHC)
Inspire ID: 1385107
Status: VALIDATED
Authors: - Wei Yang Wang - Xavier Janssen
References: none listed
Beams: p+ p+
Beam energies: (1380.0, 1380.0)GeV
Run details: - Requires inclusive inelastic events (non-diffractive and inelastic diffractive). The profile plots require large statistics.
A measurement of the underlying event (UE) activity in proton-proton collisions is performed using events with charged-particle jets produced in the central pseudorapidity region (|η|jet < 2) and with transverse momentum 1 ≤ pTjet < 100~. The analysis uses a data sample collected at a centre-of-mass energy of 2.76~with the CMS experiment at the LHC. The UE activity is measured as a function of pTjet in terms of the average multiplicity and scalar sum of transverse momenta of charged particles, with |η| < 2 and pT > 0.5~, in the azimuthal region transverse to the highest-pT jet direction. By further dividing the transverse region into two regions of smaller and larger activity, various components of the UE activity are separated.
Source
code:CMS_2015_I1385107.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/FastJets.hh"
namespace Rivet {
/// CMS UE charged particles vs. leading jet at 2.76 TeV
class CMS_2015_I1385107 : public Analysis {
public:
/// Constructor
CMS_2015_I1385107() : Analysis("CMS_2015_I1385107"),
ETACUT(2.0),
AREATOT(2*ETACUT * 2*M_PI),
AREA3(AREATOT / 3.),
AREA6(AREATOT / 6.)
{ }
/// Book histograms and initialise projections before the run
void init() {
const ChargedFinalState cfs(Cuts::abseta < 2 && Cuts::pT > 500*MeV);
declare(cfs, "CFS");
const ChargedFinalState cfsforjet(Cuts::abseta < 2.5 && Cuts::pT > 500*MeV);
const FastJets jetpro(cfsforjet, JetAlg::SISCONE, 0.5);
declare(jetpro, "Jets");
book(_h_Nch_TransAVE_vs_pT ,1, 1, 1); // Nch vs. pT_max (TransAVE)
book(_h_Sum_TransAVE_vs_pT ,2, 1, 1); // sum(pT) vs. pT_max (TransAVE)
book(_h_Nch_TransMAX_vs_pT ,3, 1, 1); // Nch vs. pT_max (TransMAX)
book(_h_Sum_TransMAX_vs_pT ,4, 1, 1); // sum(pT) vs. pT_max (TransMAX)
book(_h_Nch_TransMIN_vs_pT ,5, 1, 1); // Nch vs. pT_max (TransMIN)
book(_h_Sum_TransMIN_vs_pT ,6, 1, 1); // sum(pT) vs. pT_max (TransMIN)
book(_h_Nch_TransDIF_vs_pT ,7, 1, 1); // Nch vs. pT_max (TransDIF)
book(_h_Sum_TransDIF_vs_pT ,8, 1, 1); // sum(pT) vs. pT_max (TransDIF)
}
/// Local definition of a signed dphi, for use in differentating L and R trans regions
double signedDeltaPhi(double jetphi, double partphi) {
double delta = partphi - jetphi;
while (delta <= -PI) delta += 2 * PI;
while (delta > PI) delta -= 2 * PI;
return delta;
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// Find the lead jet, applying a restriction that the jets must be within |eta| < 2.
FourMomentum p_lead;
for (const Jet& j : apply<FastJets>(event, "Jets").jetsByPt(Cuts::abseta < 2.0 && Cuts::pT > 1*GeV)) {
p_lead = j.momentum();
break;
}
if (p_lead.isZero()) vetoEvent;
const double phi_lead = p_lead.phi();
const double pT_lead = p_lead.pT();
// Loop on charged particles and separate Left and Right transverse regions
Particles particles = apply<ChargedFinalState>(event, "CFS").particlesByPt();
int nch_TransLeft = 0, nch_TransRight = 0;
double ptSum_TransLeft = 0., ptSum_TransRight = 0.;
for (const Particle& p : particles) {
const double dphi = signedDeltaPhi(phi_lead, p.momentum().phi());
if (!inRange(fabs(dphi), PI/3, 2*PI/3.)) continue; //< only fill trans regions
if (dphi < 0) { // Transverse Right region
nch_TransRight += 1;
ptSum_TransRight += p.pT() / GeV;
} else if (dphi > 0) { // Transverse Left region
nch_TransLeft += 1;
ptSum_TransLeft += p.pT() / GeV;
}
}
// Translate to min and max (+sum and diff) Transverse regions
const int nch_TransMIN = std::min(nch_TransLeft, nch_TransRight);
const int nch_TransMAX = std::max(nch_TransLeft, nch_TransRight);
const int nch_TransSUM = nch_TransMAX + nch_TransMIN;
const int nch_TransDIF = nch_TransMAX - nch_TransMIN;
//
const double ptSum_TransMIN = std::min(ptSum_TransLeft, ptSum_TransRight);
const double ptSum_TransMAX = std::max(ptSum_TransLeft, ptSum_TransRight);
const double ptSum_TransSUM = ptSum_TransMAX + ptSum_TransMIN;
const double ptSum_TransDIF = ptSum_TransMAX - ptSum_TransMIN;
// Fill profiles
_h_Nch_TransMIN_vs_pT->fill(pT_lead/GeV, 1/AREA6 * nch_TransMIN);
_h_Sum_TransMIN_vs_pT->fill(pT_lead/GeV, 1/AREA6 * ptSum_TransMIN);
//
_h_Nch_TransMAX_vs_pT->fill(pT_lead/GeV, 1/AREA6 * nch_TransMAX);
_h_Sum_TransMAX_vs_pT->fill(pT_lead/GeV, 1/AREA6 * ptSum_TransMAX);
//
_h_Nch_TransAVE_vs_pT->fill(pT_lead/GeV, 1/AREA3 * nch_TransSUM);
_h_Sum_TransAVE_vs_pT->fill(pT_lead/GeV, 1/AREA3 * ptSum_TransSUM);
//
_h_Nch_TransDIF_vs_pT->fill(pT_lead/GeV, 1/AREA6 * nch_TransDIF);
_h_Sum_TransDIF_vs_pT->fill(pT_lead/GeV, 1/AREA6 * ptSum_TransDIF);
}
private:
// Data members like post-cuts event weight counters go here
const double ETACUT, AREATOT, AREA3, AREA6;
/// Histograms
Profile1DPtr _h_Nch_TransAVE_vs_pT, _h_Sum_TransAVE_vs_pT;
Profile1DPtr _h_Nch_TransDIF_vs_pT, _h_Sum_TransDIF_vs_pT;
Profile1DPtr _h_Nch_TransMIN_vs_pT, _h_Sum_TransMIN_vs_pT;
Profile1DPtr _h_Nch_TransMAX_vs_pT, _h_Sum_TransMAX_vs_pT;
};
RIVET_DECLARE_PLUGIN(CMS_2015_I1385107);
}