Rivet analyses

title: ATLAS_2012_I1124167

Measurement of charged-particle event shape variables

Experiment: ATLAS (LHC)

Inspire ID: 1124167

Status: VALIDATED

Authors: - Deepak Kar

References: - Expt page: ATLAS-STDM-2011-32 - arXiv: 1207.6915 - Phys.Rev. D88 (2013) 032004 - 10.1103/PhysRevD.88.032004

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - Minimum bias events with at least 6 charged particles at 7 TeV

The measurement of charged-particle event shape variables is presented in inclusive inelastic $pp$ collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented.

Source code:ATLAS_2012_I1124167.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/Sphericity.hh"

include "Rivet/Projections/Thrust.hh"

namespace Rivet {

/// Rivet analysis class for ATLAS min bias event shapes class ATLAS_2012_I1124167 : public Analysis { public:

/// Constructor
ATLAS_2012_I1124167()
    : Analysis("ATLAS_2012_I1124167") { }


/// Initialization, called once before running
void init() {
  // Projections
  ChargedFinalState cfs(Cuts::abseta < 2.5 && Cuts::pT > 0.5 * GeV);
  declare(cfs, "CFS");

  // Book histograms
  book(_hist_T_05_25, 1, 1, 1);
  book(_hist_T_05, 2, 1, 1);
  book(_hist_T_25_50, 1, 1, 2);
  book(_hist_T_25, 2, 1, 2);
  book(_hist_T_50_75, 1, 1, 3);
  book(_hist_T_50, 2, 1, 3);
  book(_hist_T_75_100, 1, 1, 4);
  book(_hist_T_75, 2, 1, 4);
  book(_hist_T_100, 2, 1, 5);

  book(_hist_TM_05_25, 3, 1, 1);
  book(_hist_TM_05, 4, 1, 1);
  book(_hist_TM_25_50, 3, 1, 2);
  book(_hist_TM_25, 4, 1, 2);
  book(_hist_TM_50_75, 3, 1, 3);
  book(_hist_TM_50, 4, 1, 3);
  book(_hist_TM_75_100, 3, 1, 4);
  book(_hist_TM_75, 4, 1, 4);
  book(_hist_TM_100, 4, 1, 5);

  book(_hist_S_05_25, 5, 1, 1);
  book(_hist_S_05, 6, 1, 1);
  book(_hist_S_25_50, 5, 1, 2);
  book(_hist_S_25, 6, 1, 2);
  book(_hist_S_50_75, 5, 1, 3);
  book(_hist_S_50, 6, 1, 3);
  book(_hist_S_75_100, 5, 1, 4);
  book(_hist_S_75, 6, 1, 4);
  book(_hist_S_100, 6, 1, 5);


  book(_hist_T_N, 7, 1, 1);
  book(_hist_TM_N, 7, 1, 2);
  book(_hist_S_N, 7, 1, 3);

  book(_hist_T_S, 8, 1, 1);
  book(_hist_TM_S, 8, 1, 2);
  book(_hist_S_S, 8, 1, 3);
}


void analyze(const Event& event) {

  // CFS projection and particles
  const Particles& particles500 = apply<ChargedFinalState>(event, "CFS").particlesByPt();

  // Require at least 6 charged particles
  if (particles500.size() < 6) vetoEvent;

  // Preparation for Thrust calculation
  vector<Vector3> momenta;

  // Counters
  double num500 = 0;
  double ptSum500 = 0;

  double pTlead = particles500[0].pT() / GeV;

  // Loop over particles
  for (const Particle& p : particles500) {
    num500 += 1;
    ptSum500 += p.pT() / GeV;

    // Transverse Thrust calculation requires p_z to be set to 0
    Vector3 mom = p.p3();
    mom.setZ(0.0);
    momenta.push_back(mom);
  }

  // If only 2 particles, we need to use a ghost so that Thrust.calc() doesn't return 1.
  if (momenta.size() == 2) {
    momenta.push_back(Vector3(1e-10 * MeV, 0., 0.));
  }

  // Actual thrust calculation
  Thrust thrust;
  thrust.calc(momenta);

  const double T = 1.0 - thrust.thrust();
  const double TM = thrust.thrustMajor();

  Sphericity sphericity;
  sphericity.calc(momenta);

  double S = sphericity.transSphericity();
  if (std::isnan(S)) S = -1.0; // put this in the underflow bin

  // Fill histos, most inclusive first

  // pTlead > 0.5
  _hist_T_05->fill(T);
  _hist_TM_05->fill(TM);
  _hist_S_05->fill(S);

  // pTlead 0.5 - 2.5
  if (pTlead <= 2.5) {
    _hist_T_05_25->fill(T);
    _hist_TM_05_25->fill(TM);
    _hist_S_05_25->fill(S);
  }

  // pTlead > 2.5
  if (pTlead > 2.5) {
    _hist_T_25->fill(T);
    _hist_TM_25->fill(TM);
    _hist_S_25->fill(S);
  }

  // pTlead 2.5 - .5
  if (inRange(pTlead, 2.5, 5.0)) {
    _hist_T_25_50->fill(T);
    _hist_TM_25_50->fill(TM);
    _hist_S_25_50->fill(S);
  }

  // pTlead > 5
  if (pTlead > 5) {
    _hist_T_50->fill(T);
    _hist_TM_50->fill(TM);
    _hist_S_50->fill(S);
  }

  // pTlead 5 - 7.5
  if (inRange(pTlead, 5.0, 7.5)) {
    _hist_T_50_75->fill(T);
    _hist_TM_50_75->fill(TM);
    _hist_S_50_75->fill(S);
  }

  // pTlead > 7.5
  if (pTlead > 7.5) {
    _hist_T_75->fill(T);
    _hist_TM_75->fill(TM);
    _hist_S_75->fill(S);
  }

  // pTlead 7.5 - 10
  if (inRange(pTlead, 7.5, 10)) {
    _hist_T_75_100->fill(T);
    _hist_TM_75_100->fill(TM);
    _hist_S_75_100->fill(S);
  }

  // pTlead > 10
  if (pTlead > 10) {
    _hist_T_100->fill(T);
    _hist_TM_100->fill(TM);
    _hist_S_100->fill(S);
  }


  // Profiles Nch vs. ES
  _hist_T_N->fill(num500, T);
  _hist_TM_N->fill(num500, TM);
  _hist_S_N->fill(num500, S);

  // Profiles pTsum vs. ES
  _hist_T_S->fill(ptSum500, T);
  _hist_TM_S->fill(ptSum500, TM);
  _hist_S_S->fill(ptSum500, S);
}


void finalize() {
  normalize(_hist_T_05_25);
  normalize(_hist_T_05);
  normalize(_hist_T_25_50);
  normalize(_hist_T_25);
  normalize(_hist_T_50_75);
  normalize(_hist_T_50);
  normalize(_hist_T_75_100);
  normalize(_hist_T_75);
  normalize(_hist_T_100);

  normalize(_hist_TM_05_25);
  normalize(_hist_TM_05);
  normalize(_hist_TM_25_50);
  normalize(_hist_TM_25);
  normalize(_hist_TM_50_75);
  normalize(_hist_TM_50);
  normalize(_hist_TM_75_100);
  normalize(_hist_TM_75);
  normalize(_hist_TM_100);

  normalize(_hist_S_05_25);
  normalize(_hist_S_05);
  normalize(_hist_S_25_50);
  normalize(_hist_S_25);
  normalize(_hist_S_50_75);
  normalize(_hist_S_50);
  normalize(_hist_S_75_100);
  normalize(_hist_S_75);
  normalize(_hist_S_100);
}

private:

Histo1DPtr _hist_T_05_25, _hist_T_05, _hist_T_25_50, _hist_T_25, _hist_T_50_75, _hist_T_50,
    _hist_T_75_100, _hist_T_75, _hist_T_100;
Histo1DPtr _hist_TM_05_25, _hist_TM_05, _hist_TM_25_50, _hist_TM_25, _hist_TM_50_75, _hist_TM_50,
    _hist_TM_75_100, _hist_TM_75, _hist_TM_100;
Histo1DPtr _hist_S_05_25, _hist_S_05, _hist_S_25_50, _hist_S_25, _hist_S_50_75, _hist_S_50,
    _hist_S_75_100, _hist_S_75, _hist_S_100;
Profile1DPtr _hist_T_N, _hist_TM_N, _hist_S_N;
Profile1DPtr _hist_T_S, _hist_TM_S, _hist_S_S;

};

RIVET_DECLARE_PLUGIN(ATLAS_2012_I1124167);

} ```