Rivet analyses
Forward-backward asymmetry A_FB in Drell-Yan lepton pairs at sqrt(s) = 7 TeV
Experiment: CMS (LHC)
Inspire ID: 1122847
Status: VALIDATED
Authors: - Markus Radziej
References: - Phys. Lett. B 718 (2013) 752 - DOI: 10.1016/j.physletb.2012.10.082 - arXiv: 1207.3973
Beams: p+ p+
Beam energies: (3500.0, 3500.0)GeV
Run details: - Drell-Yan events with an electron or muon final state are necessary. High statistics as well as a NLO generator are recommended for a good agreement
This analysis measures the forward-backward asymmetry AFB in Drell-Yan events at a center-of-mass energy of 7 TeV. Both the individual and combined electron and muon pair channels are analyzed. In four rapidity regions, AFB is given as a function of the lepton mass. The data, recorded with the CMS detector, corresponds to an integrated luminosity of 5 fb−1.
Source
code:CMS_2013_I1122847.cc
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/DileptonFinder.hh"
namespace Rivet {
class CMS_2013_I1122847 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2013_I1122847);
/// Book histograms and initialise projections before the run
void init() {
Cut cuts_mu = Cuts::abseta < 2.4 && Cuts::pT > 20*GeV;
DileptonFinder zfinder_mu(91.2*GeV, 0.0, cuts_mu && Cuts::abspid == PID::MUON, Cuts::mass > 40*GeV);
declare(zfinder_mu, "zfinder_mu");
Cut cuts_el = Cuts::pT > 20*GeV && Cuts::abseta < 2.4 && !Cuts::absetaIn(1.447, 1.57);
DileptonFinder zfinder_el(91.2*GeV, 0.0, cuts_el && Cuts::abspid == PID::ELECTRON, Cuts::mass > 40*GeV);
declare(zfinder_el, "zfinder_el");
/// Histograms
// dimuon
book(_hist_mm_100_num, "TMP/mm_100_num", refData(1, 1, 1));
book(_hist_mm_125_num, "TMP/mm_125_num", refData(1, 1, 2));
book(_hist_mm_150_num, "TMP/mm_150_num", refData(1, 1, 3));
book(_hist_mm_240_num, "TMP/mm_240_num", refData(1, 1, 4));
book(_hist_mm_100_den, "TMP/mm_100_den", refData(1, 1, 1));
book(_hist_mm_125_den, "TMP/mm_125_den", refData(1, 1, 2));
book(_hist_mm_150_den, "TMP/mm_150_den", refData(1, 1, 3));
book(_hist_mm_240_den, "TMP/mm_240_den", refData(1, 1, 4));
// Dielectron
book(_hist_ee_100_num, "TMP/ee_100_num", refData(2, 1, 1));
book(_hist_ee_125_num, "TMP/ee_125_num", refData(2, 1, 2));
book(_hist_ee_150_num, "TMP/ee_150_num", refData(2, 1, 3));
book(_hist_ee_240_num, "TMP/ee_240_num", refData(2, 1, 4));
book(_hist_ee_100_den, "TMP/ee_100_den", refData(2, 1, 1));
book(_hist_ee_125_den, "TMP/ee_125_den", refData(2, 1, 2));
book(_hist_ee_150_den, "TMP/ee_150_den", refData(2, 1, 3));
book(_hist_ee_240_den, "TMP/ee_240_den", refData(2, 1, 4));
// Dilepton
book(_hist_ll_100_num, "TMP/ll_100_num", refData(3, 1, 1));
book(_hist_ll_125_num, "TMP/ll_125_num", refData(3, 1, 2));
book(_hist_ll_150_num, "TMP/ll_150_num", refData(3, 1, 3));
book(_hist_ll_240_num, "TMP/ll_240_num", refData(3, 1, 4));
book(_hist_ll_100_den, "TMP/ll_100_den", refData(3, 1, 1));
book(_hist_ll_125_den, "TMP/ll_125_den", refData(3, 1, 2));
book(_hist_ll_150_den, "TMP/ll_150_den", refData(3, 1, 3));
book(_hist_ll_240_den, "TMP/ll_240_den", refData(3, 1, 4));
book(_s_mm_100, 1, 1, 1);
book(_s_mm_125, 1, 1, 2);
book(_s_mm_150, 1, 1, 3);
book(_s_mm_240, 1, 1, 4);
book(_s_ee_100, 2, 1, 1);
book(_s_ee_125, 2, 1, 2);
book(_s_ee_150, 2, 1, 3);
book(_s_ee_240, 2, 1, 4);
book(_s_ll_100, 3, 1, 1);
book(_s_ll_125, 3, 1, 2);
book(_s_ll_150, 3, 1, 3);
book(_s_ll_240, 3, 1, 4);
}
double cosThetaCS(const Particle& l1, const Particle& l2) {
const FourMomentum mom1 = l1.mom();
const FourMomentum mom2 = l2.mom();
const FourMomentum mom12 = mom1 + mom2;
const double Q = mom12.mass();
const double QT = mom12.pT();
const double QZ = mom12.pz();
/// @todo Why include factors of sqrt2 which then get immediately multiplied then divided out?
const double sqrt2 = sqrt(2.0);
/// @todo Can be done more nicely via PID-ordered references to mom1, mom2
const double P1p = ((l1.pid() > 0) ? (mom1.E() + mom1.pz()) : (mom2.E() + mom2.pz())) / sqrt2;
const double P1m = ((l1.pid() > 0) ? (mom1.E() - mom1.pz()) : (mom2.E() - mom2.pz())) / sqrt2;
const double P2p = ((l1.pid() > 0) ? (mom2.E() + mom2.pz()) : (mom1.E() + mom1.pz())) / sqrt2;
const double P2m = ((l1.pid() > 0) ? (mom2.E() - mom2.pz()) : (mom1.E() - mom1.pz())) / sqrt2;
const double cosThetaCS = sign(QZ) * (2 / (Q * add_quad(Q, QT))) * (P1p*P2m - P1m*P2p);
return cosThetaCS;
}
/// Perform the per-event analysis
void analyze(const Event& event) {
const DileptonFinder& zfinder_el = apply<DileptonFinder>(event, "zfinder_el");
if (zfinder_el.bosons().size() > 0) {
const Particle& z = zfinder_el.bosons()[0];
const Particle& l1 = zfinder_el.constituents()[0];
const Particle& l2 = zfinder_el.constituents()[1];
// Prepare variables for filling
const double rap = z.absrap();
const double costhetacs = cosThetaCS(l1, l2);
const double sgn = sign(costhetacs);
// Fill the histograms
if (rap < 1.0) {
_hist_ee_100_num->fill(z.mass(), sgn);
_hist_ll_100_num->fill(z.mass(), sgn);
_hist_ee_100_den->fill(z.mass());
_hist_ll_100_den->fill(z.mass());
} else if (rap < 1.25) {
_hist_ee_125_num->fill(z.mass(), sgn);
_hist_ll_125_num->fill(z.mass(), sgn);
_hist_ee_125_den->fill(z.mass());
_hist_ll_125_den->fill(z.mass());
} else if (rap < 1.50) {
_hist_ee_150_num->fill(z.mass(), sgn);
_hist_ll_150_num->fill(z.mass(), sgn);
_hist_ee_150_den->fill(z.mass());
_hist_ll_150_den->fill(z.mass());
} else if (rap < 2.40) {
_hist_ee_240_num->fill(z.mass(), sgn);
_hist_ll_240_num->fill(z.mass(), sgn);
_hist_ee_240_den->fill(z.mass());
_hist_ll_240_den->fill(z.mass());
}
}
const DileptonFinder& zfinder_mu = apply<DileptonFinder>(event, "zfinder_mu");
if (zfinder_mu.bosons().size() > 0) {
const Particle& z = zfinder_mu.bosons()[0];
const Particle& l1 = zfinder_mu.constituents()[0];
const Particle& l2 = zfinder_mu.constituents()[1];
// Prepare variables for filling
const double rap = z.absrap();
const double costhetacs = cosThetaCS(l1, l2);
const double sgn = sign(costhetacs);
// Fill the histograms
if (rap < 1.0) {
_hist_mm_100_num->fill(z.mass(), sgn);
_hist_ll_100_num->fill(z.mass(), sgn);
_hist_mm_100_den->fill(z.mass());
_hist_ll_100_den->fill(z.mass());
} else if (rap < 1.25) {
_hist_mm_125_num->fill(z.mass(), sgn);
_hist_ll_125_num->fill(z.mass(), sgn);
_hist_mm_125_den->fill(z.mass());
_hist_ll_125_den->fill(z.mass());
} else if (rap < 1.50) {
_hist_mm_150_num->fill(z.mass(), sgn);
_hist_ll_150_num->fill(z.mass(), sgn);
_hist_mm_150_den->fill(z.mass());
_hist_ll_150_den->fill(z.mass());
} else if (rap < 2.40) {
_hist_mm_240_num->fill(z.mass(), sgn);
_hist_ll_240_num->fill(z.mass(), sgn);
_hist_mm_240_den->fill(z.mass());
_hist_ll_240_den->fill(z.mass());
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
divide(_hist_mm_100_num, _hist_mm_100_den, _s_mm_100);
divide(_hist_mm_125_num, _hist_mm_125_den, _s_mm_125);
divide(_hist_mm_150_num, _hist_mm_150_den, _s_mm_150);
divide(_hist_mm_240_num, _hist_mm_240_den, _s_mm_240);
divide(_hist_ee_100_num, _hist_ee_100_den, _s_ee_100);
divide(_hist_ee_125_num, _hist_ee_125_den, _s_ee_125);
divide(_hist_ee_150_num, _hist_ee_150_den, _s_ee_150);
divide(_hist_ee_240_num, _hist_ee_240_den, _s_ee_240);
divide(_hist_ll_100_num, _hist_ll_100_den, _s_ll_100);
divide(_hist_ll_125_num, _hist_ll_125_den, _s_ll_125);
divide(_hist_ll_150_num, _hist_ll_150_den, _s_ll_150);
divide(_hist_ll_240_num, _hist_ll_240_den, _s_ll_240);
}
private:
/// Histograms
Histo1DPtr _hist_ee_100_num, _hist_ee_125_num, _hist_ee_150_num, _hist_ee_240_num;
Histo1DPtr _hist_ee_100_den, _hist_ee_125_den, _hist_ee_150_den, _hist_ee_240_den;
Histo1DPtr _hist_mm_100_num, _hist_mm_125_num, _hist_mm_150_num, _hist_mm_240_num;
Histo1DPtr _hist_mm_100_den, _hist_mm_125_den, _hist_mm_150_den, _hist_mm_240_den;
Histo1DPtr _hist_ll_100_num, _hist_ll_125_num, _hist_ll_150_num, _hist_ll_240_num;
Histo1DPtr _hist_ll_100_den, _hist_ll_125_den, _hist_ll_150_den, _hist_ll_240_den;
Estimate1DPtr _s_ee_100, _s_ee_125, _s_ee_150, _s_ee_240;
Estimate1DPtr _s_mm_100, _s_mm_125, _s_mm_150, _s_mm_240;
Estimate1DPtr _s_ll_100, _s_ll_125, _s_ll_150, _s_ll_240;
};
RIVET_DECLARE_PLUGIN(CMS_2013_I1122847);
}