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CMS_2011_S9088458

Measurement of ratio of the 3-jet over 2-jet cross section in $pp$ collisions at $\sqrt{s} = 7$ TeV
Experiment: CMS (LHC)
Inspire ID: 912560
Status: VALIDATED
Authors:
  • Tomo Umer
References:
  • Phys. Lett. B 702 (2011) 336
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Inclusive QCD at 7 TeV. $\hat{p_\perp}$ (or equivalent) greater than 30 GeV

A measurement of the ratio of the inclusive 3-jet to 2-jet cross sections as a function of the total jet transverse momentum, $H_T$, in the range $0.2 < H_T < 2.5$ TeV is presented. The data have been collected at a proton--proton centre-of-mass energy of 7 TeV with the CMS detector at the LHC, and correspond to an integrated luminosity of 36/pb. Jets are anti-$k_t$ with $R = 0.5$, $p_\perp > 50 \text{GeV}$ and $|\eta| < 2.5$.

Source code: CMS_2011_S9088458.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4#include "Rivet/Projections/FastJets.hh"
 5
 6namespace Rivet {
 7
 8
 9   /// CMS ratio of 3-jet to 2-jet cross-sections
10   class CMS_2011_S9088458 : public Analysis {
11   public:
12
13     RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_S9088458);
14
15
16     void init() {
17       FinalState fs;
18       FastJets akt(fs, FastJets::ANTIKT, 0.5);
19       declare(akt, "antikT");
20
21       book(_h_tmp_dijet , "TMP/dijet", refData(1, 1, 1));
22       book(_h_tmp_trijet, "TMP/trijet", refData(1, 1, 1));
23       book(_h_r32, 1, 1, 1);
24     }
25
26
27     void analyze(const Event & event) {
28       const double weight = 1.0;
29
30       Jets highpT_jets;
31       double HT = 0;
32       for(const Jet & jet : apply<JetAlg>(event, "antikT").jetsByPt(50.0*GeV)) {
33         if (jet.abseta() < 2.5) {
34           highpT_jets.push_back(jet);
35           HT += jet.pT();
36         }
37       }
38       if (highpT_jets.size() < 2) vetoEvent;
39       if (highpT_jets.size() >= 2) _h_tmp_dijet->fill(HT/TeV, weight);
40       if (highpT_jets.size() >= 3) _h_tmp_trijet->fill(HT/TeV, weight);
41     }
42
43
44     void finalize() {
45       divide(_h_tmp_trijet, _h_tmp_dijet, _h_r32);
46     }
47
48
49   private:
50
51     /// @{
52     Histo1DPtr _h_tmp_dijet, _h_tmp_trijet;
53     Scatter2DPtr _h_r32;
54     /// @}
55
56  };
57
58
59
60  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_S9088458, CMS_2011_I912560);
61
62}