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