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ATLAS_2012_I1118269

$b$-hadron production cross-section using decays to $D^*\mu^-X$ at $\sqrt{s} = 7$ TeV
Experiment: ATLAS (LHC)
Inspire ID: 1118269
Status: VALIDATED
Authors:
  • Andy Buckley
  • Sercan Sen
  • Peter Skands
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • pp to b-hadron + X at 7 TeV, i.e. switch on "HardQCD:gg2bbbar" and "HardQCD:qqbar2bbbar" flags in Pythia8.

Measurement of $b$-hadron production cross section using 3.3 pb$^{-1}$ of integrated luminosity, collected during the 2010 LHC run. The $b$-hadrons are selected by partially reconstructing $D^{*}\mu^-X$ final states using only direct semileptonic decays of $b$ to $D^*\mu^-X$. Differential cross sections as functions of $p_\perp$ and $|\eta|$.

Source code: ATLAS_2012_I1118269.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Particle.hh"
 4
 5namespace Rivet {
 6
 7
 8  class ATLAS_2012_I1118269 : public Analysis {
 9  public:
10
11    ATLAS_2012_I1118269() : Analysis("ATLAS_2012_I1118269")
12    {  }
13
14    void init() {
15      book(_h_sigma_vs_pt  ,1, 1, 1);
16      book(_h_sigma_vs_eta ,2, 1, 1);
17    }
18
19    /// Perform the per-event analysis
20    void analyze(const Event& event) {
21      Particles bhadrons;
22      for(ConstGenParticlePtr p: HepMCUtils::particles(event.genEvent())) {
23
24        if (!( PID::isHadron( p->pdg_id() ) && PID::hasBottom( p->pdg_id() )) ) continue;
25
26        ConstGenVertexPtr dv = p->end_vertex();
27
28        /// @todo In future, convert to use built-in 'last B hadron' function
29        bool hasBdaughter = false;
30        if ( PID::isHadron( p->pdg_id() ) && PID::hasBottom( p->pdg_id() )) { // b-hadron selection
31          if (dv) {
32            /// @todo particles_out_const_iterator is deprecated in HepMC3
33            for(ConstGenParticlePtr pp: HepMCUtils::particles(dv, Relatives::CHILDREN)){
34              if ( PID::isHadron( pp->pdg_id() ) && PID::hasBottom( pp->pdg_id()) ) {
35                hasBdaughter = true;
36              }
37            }
38          }
39        }
40        if (hasBdaughter) continue;
41
42        bhadrons += Particle(*p);
43      }
44
45      for (const Particle& particle : bhadrons) {
46        double eta = particle.eta();
47        double pt = particle.pT();
48
49        if (!(inRange(eta, -2.5, 2.5))) continue;
50        if (pt < 9.*GeV) continue;
51
52        _h_sigma_vs_pt->fill(pt);
53        _h_sigma_vs_eta->fill(fabs(eta));
54
55      }
56
57    }
58
59
60    void finalize() {
61      scale(_h_sigma_vs_pt,  crossSection()/nanobarn/sumOfWeights());
62      scale(_h_sigma_vs_eta, crossSection()/microbarn/sumOfWeights());
63    }
64
65
66  private:
67
68    Histo1DPtr _h_sigma_vs_pt;
69    Histo1DPtr _h_sigma_vs_eta;
70
71  };
72
73
74  RIVET_DECLARE_PLUGIN(ATLAS_2012_I1118269);
75
76}