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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: 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
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/ChargedFinalState.hh"
 4#include "Rivet/Projections/IdentifiedFinalState.hh"
 5
 6namespace Rivet {
 7
 8
 9  /// Exclusive photon-photon production of muon pairs at 7 TeV
10  class CMS_2011_I954992 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_I954992);
15
16
17    void init() {
18      ChargedFinalState cfs(Cuts::abseta < 2.4);
19      declare(cfs,"CFS");
20
21      // Get muons which pass the initial kinematic cuts
22      IdentifiedFinalState muon_fs(Cuts::abseta < 2.1 && Cuts::pT > 4*GeV);
23      muon_fs.acceptIdPair(PID::MUON);
24      declare(muon_fs, "MUON_FS");
25
26      book(_h_sigma ,1,1,1);
27    }
28
29
30    void analyze(const Event& event) {
31
32      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
33      if (cfs.size() != 2) vetoEvent; // no other charged particles in 2.4
34
35      const Particles& muonFS = apply<IdentifiedFinalState>(event, "MUON_FS").particles();
36      if (muonFS.size() != 2) vetoEvent;
37
38      if (muonFS[0].charge() != muonFS[1].charge()) {
39         const double dimuon_mass = (muonFS[0].momentum() + muonFS[1].momentum()).mass();
40         const double v_angle     = muonFS[0].momentum().angle(muonFS[1].momentum());
41         const double dPhi        = deltaPhi(muonFS[0], muonFS[1]);
42         const double deltaPt     = fabs(muonFS[0].pT() - muonFS[1].pT());
43
44         if (dimuon_mass >= 11.5*GeV &&
45             v_angle < 0.95*PI       &&
46             dPhi    > 0.9*PI        &&
47             deltaPt < 1.*GeV        ) {
48           _h_sigma->fill(7000);
49         }
50      }
51    }
52
53
54    /// Normalise histograms etc., after the run
55    void finalize() {
56      scale(_h_sigma, crossSection()/picobarn/sumOfWeights());
57    }
58
59
60    /// Histogram
61    BinnedHistoPtr<int> _h_sigma;
62
63  };
64
65
66  RIVET_DECLARE_PLUGIN(CMS_2011_I954992);
67
68}