Rivet analyses

Production cross-sections of muons from b hadron decays in pp collisions

Experiment: CMS (LHC)

Inspire ID: 884811

Status: VALIDATED

Authors: - Wolfram Erdmann

References: - JHEP 1103,090 - DOI: 10.1007/JHEP03(2011)090 - arXiv: 1101.3512

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - Inclusive QCD at 7 TeV, with no pT cuts.

A measurement of the b-hadron production cross-section in proton-proton collisions at $\sqrt{s} = 7$~TeV. The dataset, corresponding to 85 inverse nanobarns, was recorded with the CMS experiment at the LHC using a low-threshold single-muon trigger. Events are selected by the presence of a muon with transverse momentum greater than 6 GeV with respect to the beam direction and pseudorapidity less than 2.1. The transverse momentum of the muon with respect to the closest jet discriminates events containing b hadrons from background. The inclusive b-hadron production cross section is presented as a function of muon transverse momentum and pseudorapidity.

Source code:CMS_2011_I884811.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/IdentifiedFinalState.hh"
#include "Rivet/Particle.hh"

namespace Rivet {


  /// Production cross-sections of muons from $b$ hadron decays in $pp$ collisions
  class CMS_2011_I884811 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I884811);


    /// Book histograms and initialise projections before the run
    void init() {
      book(_h_total ,1, 1, 1);
      book(_h_mupt  ,2, 1, 1);
      book(_h_mueta ,3, 1, 1);

      IdentifiedFinalState ifs(Cuts::abseta < 2.1 && Cuts::pT > 6*GeV);
      ifs.acceptIdPair(PID::MUON);
      declare(ifs, "IFS");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

      // a b-quark must have been produced
      /// @todo Ouch. Use hadron tagging...
      int nb = 0;
      for(ConstGenParticlePtr p: HepMCUtils::particles(event.genEvent())) {
        if (abs(p->pdg_id()) == PID::BQUARK) nb += 1;
      }
      if (nb == 0) vetoEvent;

      // Event must contain a muon
      Particles muons = apply<IdentifiedFinalState>(event, "IFS").particlesByPt();
      if (muons.size() < 1) vetoEvent;

      FourMomentum pmu = muons[0].momentum();
      _h_total->fill(7000);
      _h_mupt->fill(pmu.pT()/GeV);
      _h_mueta->fill(pmu.eta()/GeV);
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_total, crossSection()/microbarn/sumOfWeights());
      scale(_h_mupt,  crossSection()/nanobarn/sumOfWeights());
      scale(_h_mueta, crossSection()/nanobarn/sumOfWeights());
    }


  private:

    /// @{
    BinnedHistoPtr<int> _h_total;
    Histo1DPtr _h_mupt;
    Histo1DPtr _h_mueta;
    /// @}

  };



  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_I884811, CMS_2011_S8941262);

}

Aliases: - CMS_2011_S8941262