Rivet analyses

title: CMS_2011_I954992

Exclusive photon-photon production of muon pairs in proton-proton collisions at $\sqrt{s} = 7$ TeV

Experiment: CMS (LHC)

Inspire ID: 954992

Status: VALIDATED

Authors: - David d'Enterria - Jonathan Hollar - Sercan Sen

References: - arXiv: 1111.5536

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - gamma gamma TO mu+ mu- process.

A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at at a centre-of-mass energy 7 TeV with the final state $p \mu^+ \mu^- p$, is reported using data corresponding to an integrated luminosity of 40 pb$^-1$ collected in 2010. The measured cross section is obtained with a fit to the dimuon $p_T$ distribution for muon pairs with invariant mass greater than 11.5 GeV with each muon $p_T > 4$ GeV and $|\eta| < 2.1$.

Source code:CMS_2011_I954992.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

namespace Rivet {

/// Exclusive photon-photon production of muon pairs at 7 TeV class CMS_2011_I954992 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I954992);


void init() {
  ChargedFinalState cfs(Cuts::abseta < 2.4);
  declare(cfs, "CFS");

  // Get muons which pass the initial kinematic cuts
  IdentifiedFinalState muon_fs(Cuts::abseta < 2.1 && Cuts::pT > 4 * GeV);
  muon_fs.acceptIdPair(PID::MUON);
  declare(muon_fs, "MUON_FS");

  book(_h_sigma, 1, 1, 1);
}


void analyze(const Event& event) {

  const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
  if (cfs.size() != 2) vetoEvent; // no other charged particles in 2.4

  const Particles& muonFS = apply<IdentifiedFinalState>(event, "MUON_FS").particles();
  if (muonFS.size() != 2) vetoEvent;

  if (muonFS[0].charge() != muonFS[1].charge()) {
    const double dimuon_mass = (muonFS[0].momentum() + muonFS[1].momentum()).mass();
    const double v_angle = muonFS[0].momentum().angle(muonFS[1].momentum());
    const double dPhi = deltaPhi(muonFS[0], muonFS[1]);
    const double deltaPt = fabs(muonFS[0].pT() - muonFS[1].pT());

    if (dimuon_mass >= 11.5 * GeV && v_angle < 0.95 * PI && dPhi > 0.9 * PI && deltaPt < 1. * GeV) {
      _h_sigma->fill(7000);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_sigma, crossSection() / picobarn / sumOfWeights());
}


/// Histogram
BinnedHistoPtr<int> _h_sigma;

};

RIVET_DECLARE_PLUGIN(CMS_2011_I954992);

} ```