Rivet analyses

title: ALICE_2010_I860416

Charged particle $\langle p_\perp \rangle$ vs. $N_\text{ch}$ in $pp$ collisions at 900 GeV

Experiment: ALICE (LHC)

Inspire ID: 860416

Status: VALIDATED

Authors: - Holger Schulz - Jan Fiete Grosse-Oetringhaus

References: - Phys.Lett.B693:53-68,2010 - arXiv: 1007.0719

Beams: p+ p+

Beam energies: (450.0, 450.0)GeV

Run details: - Diffractive events need to be switched on

ALICE measurement of $\langle p_\perp \rangle$ vs. $N_\text{ch}$ and invariant particle yield (as function of $p_\perp$) in proton-proton collisions at $\sqrt{s} = 900~\GeV$.

Source code:ALICE_2010_I860416.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {

class ALICE_2010_I860416 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2010_I860416);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {

  ChargedFinalState cfs((Cuts::etaIn(-0.8, 0.8) && Cuts::pT >= 0.15));
  declare(cfs, "CFS");

  book(_h_pT, 4, 1, 1);

  book(_h_pT_Nch_015, 11, 1, 1);
  book(_h_pT_Nch_05, 12, 1, 1);

  book(_Nevt_after_cuts, "Nevt_after_cuts");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const ChargedFinalState& charged = apply<ChargedFinalState>(event, "CFS");

  _Nevt_after_cuts->fill();

  // Get number of particles that fulfill certain pT requirements
  int Nch_015 = 0;
  int Nch_05 = 0;
  for (const Particle& p : charged.particles()) {
    double pT = p.pT() / GeV;
    if (pT < 4.0) Nch_015++;
    if (pT > 0.5 && pT < 4.0) Nch_05++;
  }

  // Now we can fill histograms
  for (const Particle& p : charged.particles()) {
    double pT = p.pT() / GeV;
    if (pT < 4.0) _h_pT_Nch_015->fill(Nch_015, pT);
    if (pT > 0.5 && pT < 4.0) _h_pT_Nch_05->fill(Nch_05, pT);

    // To get the Yield, fill appropriate weight 1/(2PI * pT * d eta)
    _h_pT->fill(pT, 1.0 / (TWOPI * pT * 1.6));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_pT, 1.0 / *_Nevt_after_cuts);
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_pT;
Profile1DPtr _h_pT_Nch_015;
Profile1DPtr _h_pT_Nch_05;
CounterPtr _Nevt_after_cuts;
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(ALICE_2010_I860416, ALICE_2010_S8706239);

} ```

Aliases: - ALICE_2010_S8706239