Rivet analyses
title: D0_2001_I559624
Tevatron Run I differential W/Z boson cross-section analysis
Experiment: D0 (Tevatron Run 1)
Inspire ID: 559624
Status: VALIDATED
Authors: - Lars Sonnenschein
References: - Phys.Lett.B517:299-308,2001 - DOI: 10.1016/S0370-2693(01)01020-6 - arXiv: hep-ex/0107012
Beams: p- p+
Beam energies: (900.0, 900.0)GeV
Run details: - $W/Z$ events with decays to first generation leptons, in $p\bar{p}$ collisions at $\sqrt{s} = 1800~\GeV$
Measurement of differential W/Z boson cross section and ratio in $p \bar{p}$ collisions at center-of-mass energy $\sqrt{s} = 1.8~\TeV$. The data cover electrons and neutrinos in a pseudorapidity range of -2.5 to 2.5.
Source code:D0_2001_I559624.cc
```c++ // -- C++ --
include "Rivet/Analysis.hh"
include "Rivet/Projections/LeadingParticlesFinalState.hh"
include "Rivet/Projections/VetoedFinalState.hh"
namespace Rivet {
/// @brief D0 Run I differential W/Z boson cross-section analysis /// /// @author Lars Sonnenschein /// @author Andy Buckley class D0_2001_I559624 : public Analysis { public:
RIVET_DEFAULT_ANALYSIS_CTOR(D0_2001_I559624);
/// @name Analysis methods
/// @{
void init() {
// Final state projection
FinalState fs((Cuts::etaIn(-5.0, 5.0))); // corrected for detector acceptance
declare(fs, "FS");
// Z -> e- e+
LeadingParticlesFinalState eeFS(FinalState((Cuts::etaIn(-5.0, 5.0)))); //20.);
eeFS.addParticleIdPair(PID::ELECTRON);
declare(eeFS, "eeFS");
// W- -> e- nu_e~
LeadingParticlesFinalState enuFS(FinalState((Cuts::etaIn(-5.0, 5.0)))); //25.);
enuFS.addParticleId(PID::ELECTRON).addParticleId(PID::NU_EBAR);
declare(enuFS, "enuFS");
// W+ -> e+ nu_e
LeadingParticlesFinalState enubFS(FinalState((Cuts::etaIn(-5.0, 5.0)))); //25.);
enubFS.addParticleId(PID::POSITRON).addParticleId(PID::NU_E);
declare(enubFS, "enubFS");
// Remove neutrinos for isolation of final state particles
VetoedFinalState vfs(fs);
vfs.vetoNeutrinos();
declare(vfs, "VFS");
// Counters
book(_eventsFilledW, "eventsFilledW");
book(_eventsFilledZ, "eventsFilledZ");
// Histograms
book(_h_dsigdpt_w, 1, 1, 1);
book(_h_dsigdpt_z, 1, 1, 2);
book(_h_dsigdpt_scaled_z, 2, 1, 1);
}
void analyze(const Event& event) {
const LeadingParticlesFinalState& eeFS = apply<LeadingParticlesFinalState>(event, "eeFS");
// Z boson analysis
if (eeFS.particles().size() >= 2) {
// If there is a Z candidate:
// Fill Z pT distributions
double deltaM2 = 1e30, mass2(0.);
double pT = -1.;
const Particles& Zdaughters = eeFS.particles();
for (size_t ix = 0; ix < Zdaughters.size(); ++ix) {
for (size_t iy = ix + 1; iy < Zdaughters.size(); ++iy) {
if (Zdaughters[ix].pid() != -Zdaughters[iy].pid()) continue;
const FourMomentum pmom = Zdaughters[ix].momentum() + Zdaughters[iy].momentum();
double mz2 = pmom.mass2();
double dm2 = fabs(mz2 - sqr(91.118 * GeV));
if (dm2 < deltaM2) {
pT = pmom.pT();
deltaM2 = dm2;
mass2 = mz2;
}
}
}
if (pT > 0. && mass2 > 0. && inRange(sqrt(mass2) / GeV, 75.0, 105.0)) {
_eventsFilledZ->fill();
MSG_DEBUG("Z pmom.pT() = " << pT / GeV << " GeV");
_h_dsigdpt_z->fill(pT / GeV);
// return if found a Z
return;
}
}
// There is no Z -> ee candidate... so this might be a W event
const LeadingParticlesFinalState& enuFS = apply<LeadingParticlesFinalState>(event, "enuFS");
const LeadingParticlesFinalState& enubFS = apply<LeadingParticlesFinalState>(event, "enubFS");
double deltaM2 = 1e30;
double pT = -1.;
for (size_t iw = 0; iw < 2; ++iw) {
Particles Wdaughters;
Wdaughters = (iw == 0) ? enuFS.particles() : enubFS.particles();
for (size_t ix = 0; ix < Wdaughters.size(); ++ix) {
for (size_t iy = ix + 1; iy < Wdaughters.size(); ++iy) {
if (Wdaughters[ix].pid() == Wdaughters[iy].pid()) continue;
const FourMomentum pmom = Wdaughters[0].momentum() + Wdaughters[1].momentum();
double dm2 = abs(pmom.mass2() - sqr(80.4 * GeV));
if (dm2 < deltaM2) {
pT = pmom.pT();
deltaM2 = dm2;
}
}
}
}
if (pT > 0.) {
_eventsFilledW->fill();
_h_dsigdpt_w->fill(pT / GeV);
}
}
void finalize() {
// Get cross-section per event (i.e. per unit weight) from generator
const double xSecPerEvent = crossSectionPerEvent() / picobarn;
// Correct W pT distribution to W cross-section
const double xSecW = xSecPerEvent * dbl(*_eventsFilledW);
// Correct Z pT distribution to Z cross-section
const double xSecZ = xSecPerEvent * dbl(*_eventsFilledZ);
// Get W and Z pT integrals
const double wpt_integral = _h_dsigdpt_w->integral();
const double zpt_integral = _h_dsigdpt_z->integral();
// Divide and scale ratio histos
if (xSecW == 0 || wpt_integral == 0 || xSecZ == 0 || zpt_integral == 0) {
MSG_WARNING("Not filling ratio plot because input histos are empty");
}
else {
// Scale factor converts event counts to cross-sections, and inverts the
// branching ratios since only one decay channel has been analysed for each boson.
// Oh, and we put MW/MZ in, like they do in the paper.
const double MW_MZ = 0.8820; // Ratio M_W/M_Z
const double BRZEE_BRWENU = 0.033632 / 0.1073; // Ratio of branching fractions
const double scalefactor = (xSecW / wpt_integral) / (xSecZ / zpt_integral) * MW_MZ * BRZEE_BRWENU;
for (size_t ibin = 1; ibin < _h_dsigdpt_w->numBins() + 1; ibin++) {
double yval(0), yerr(0);
if (_h_dsigdpt_w->bin(ibin).sumW() != 0 && _h_dsigdpt_z->bin(ibin).sumW() != 0) {
yval = scalefactor * _h_dsigdpt_w->bin(ibin).sumW() / _h_dsigdpt_z->bin(ibin).sumW();
yerr = yval * sqrt(sqr(_h_dsigdpt_w->bin(ibin).relErrW()) + sqr(_h_dsigdpt_z->bin(ibin).errW()));
}
_h_dsigdpt_scaled_z->bin(ibin).set(yval, yerr);
}
}
// Normalize non-ratio histos
normalize(_h_dsigdpt_w, xSecW);
normalize(_h_dsigdpt_z, xSecZ);
}
/// @}
private:
/// @name Event counters for cross section normalizations
/// @{
CounterPtr _eventsFilledW;
CounterPtr _eventsFilledZ;
/// @}
/// @{
/// Histograms
Histo1DPtr _h_dsigdpt_w;
Histo1DPtr _h_dsigdpt_z;
Estimate1DPtr _h_dsigdpt_scaled_z;
/// @}
};
RIVET_DECLARE_ALIASED_PLUGIN(D0_2001_I559624, D0_2001_S4674421);
} ```
Aliases: - D0_2001_S4674421