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CMS_2011_I884811

Production cross-sections of muons from $b$ hadron decays in $pp$ collisions
Experiment: CMS (LHC)
Inspire ID: 884811
Status: VALIDATED
Authors:
  • Wolfram Erdmann
References: 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
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/IdentifiedFinalState.hh"
 4#include "Rivet/Particle.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// Production cross-sections of muons from $b$ hadron decays in $pp$ collisions
10  class CMS_2011_I884811 : public Analysis {
11  public:
12
13    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I884811);
14
15
16    /// Book histograms and initialise projections before the run
17    void init() {
18      book(_h_total ,1, 1, 1);
19      book(_h_mupt  ,2, 1, 1);
20      book(_h_mueta ,3, 1, 1);
21
22      IdentifiedFinalState ifs(Cuts::abseta < 2.1 && Cuts::pT > 6*GeV);
23      ifs.acceptIdPair(PID::MUON);
24      declare(ifs, "IFS");
25    }
26
27
28    /// Perform the per-event analysis
29    void analyze(const Event& event) {
30
31      // a b-quark must have been produced
32      /// @todo Ouch. Use hadron tagging...
33      int nb = 0;
34      for(ConstGenParticlePtr p: HepMCUtils::particles(event.genEvent())) {
35        if (abs(p->pdg_id()) == PID::BQUARK) nb += 1;
36      }
37      if (nb == 0) vetoEvent;
38
39      // Event must contain a muon
40      Particles muons = apply<IdentifiedFinalState>(event, "IFS").particlesByPt();
41      if (muons.size() < 1) vetoEvent;
42
43      FourMomentum pmu = muons[0].momentum();
44      _h_total->fill(7000);
45      _h_mupt->fill(pmu.pT()/GeV);
46      _h_mueta->fill(pmu.eta()/GeV);
47    }
48
49
50    /// Normalise histograms etc., after the run
51    void finalize() {
52      scale(_h_total, crossSection()/microbarn/sumOfWeights());
53      scale(_h_mupt,  crossSection()/nanobarn/sumOfWeights());
54      scale(_h_mueta, crossSection()/nanobarn/sumOfWeights());
55    }
56
57
58  private:
59
60    /// @{
61    BinnedHistoPtr<int> _h_total;
62    Histo1DPtr _h_mupt;
63    Histo1DPtr _h_mueta;
64    /// @}
65
66  };
67
68
69
70  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_I884811, CMS_2011_S8941262);
71
72}