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ATLAS_2010_S8591806

Charged particles at 900 GeV in ATLAS
Experiment: ATLAS (LHC 900GeV)
Inspire ID: 849050
Status: VALIDATED
Authors:
  • Frank Siegert
References: Beams: p+ p+
Beam energies: (450.0, 450.0) GeV
Run details:
  • pp QCD interactions at 900 GeV including diffractive events.

The first measurements with the ATLAS detector at the LHC. Data were collected using a minimum-bias trigger in December 2009 during proton-proton collisions at a centre of mass energy of 900 GeV. The charged- particle density, its dependence on transverse momentum and pseudorapid- ity, and the relationship between transverse momentum and charged-particle multiplicity are measured for events with at least one charged particle in the kinematic range $|\eta| < 2.5$ and $p_\perp > 500$ MeV. All data is corrected to the particle level.

Source code: ATLAS_2010_S8591806.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {


  /// @brief ATLAS minimum bias analysis at 900 GeV
  /// @author Frank Siegert
  class ATLAS_2010_S8591806 : public Analysis {
  public:

    ATLAS_2010_S8591806()
      : Analysis("ATLAS_2010_S8591806"),
        _Nevt_after_cuts(0.0)
    {    }


    void init() {
      ChargedFinalState cfs(-2.5, 2.5, 0.5*GeV);
      declare(cfs, "CFS");

      _h_dNch_deta = bookHisto1D(2, 1, 1);
      _h_dNch_dpT = bookHisto1D(3, 1, 1);
      _h_dNevt_dNch = bookHisto1D(4, 1, 1);
      _p_meanpT_Nch = bookProfile1D(5, 1, 1);
    }


    void analyze(const Event& event) {
      const double weight = event.weight();

      const ChargedFinalState& charged = apply<ChargedFinalState>(event, "CFS");
      if (charged.size() < 1) {
        vetoEvent;
      }
      _Nevt_after_cuts += weight;

      _h_dNevt_dNch->fill(charged.size(), weight);
      foreach (const Particle& p, charged.particles()) {
        double pT = p.pT()/GeV;
        _h_dNch_deta->fill(p.eta(), weight);
        _h_dNch_dpT->fill(pT, weight/pT);
        _p_meanpT_Nch->fill(charged.size(), pT, weight);
      }
    }


    void finalize() {
      double deta = 5.0;
      scale(_h_dNch_deta, 1.0/_Nevt_after_cuts);
      scale(_h_dNch_dpT, 1.0/_Nevt_after_cuts/TWOPI/deta);
      scale(_h_dNevt_dNch, 1.0/_Nevt_after_cuts);
    }


  private:

    Histo1DPtr _h_dNch_deta;
    Histo1DPtr _h_dNch_dpT;
    Histo1DPtr _h_dNevt_dNch;
    Profile1DPtr  _p_meanpT_Nch;

    double _Nevt_after_cuts;

  };


  //DECLARE_RIVET_PLUGIN(ATLAS_2010_S8591806);
  DECLARE_ALIASED_RIVET_PLUGIN(ATLAS_2010_S8591806, ATLAS_2010_I849050);

}