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CMS_2011_S8973270

$B/\bar{B}$ angular correlations based on secondary vertex reconstruction in $pp$ collisions
Experiment: CMS (LHC)
Inspire ID: 889807
Status: VALIDATED
Authors:
  • Lukas Wehrli
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Inclusive QCD at 7 TeV. A $\hat{p_\perp}$ cut (or similar) is recommended since a leading jet $p_\perp > 56$ GeV is required.

The differential $B\bar{B}$ cross-section is measured as a function of the opening angle $\Delta{R}$ and $\Delta\phi$ using data collected with the CMS detector during 2010 and corresponding to an integrated luminosity of 3.1 pb$^{-1}$. The measurement is performed for three different event energy scales, characterized by the transverse momentum of the leading jet in the event (above 56 GeV, above 84 GeV and above 120 GeV). Simulated events are normalised in the region $\Delta{R} > 2.4$ and $\Delta\phi > 3/4\pi$ respectively.

Source code: CMS_2011_S8973270.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5#include "Rivet/Projections/FastJets.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// B-Bbar angular correlations based on secondary vertex reconstruction
 11  class CMS_2011_S8973270 : public Analysis {
 12  public:
 13
 14    RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2011_S8973270);
 15
 16
 17    /// @name Analysis methods
 18    /// @{
 19
 20    void init() {
 21      FinalState fs;
 22      FastJets jetproj(fs, FastJets::ANTIKT, 0.5);
 23      jetproj.useInvisibles();
 24      declare(jetproj, "Jets");
 25
 26      UnstableParticles ufs;
 27      declare(ufs, "UFS");
 28
 29      // Book histograms
 30      book(_h_dsigma_dR_56GeV ,1,1,1);
 31      book(_h_dsigma_dR_84GeV ,2,1,1);
 32      book(_h_dsigma_dR_120GeV ,3,1,1);
 33      book(_h_dsigma_dPhi_56GeV ,4,1,1);
 34      book(_h_dsigma_dPhi_84GeV ,5,1,1);
 35      book(_h_dsigma_dPhi_120GeV ,6,1,1);
 36
 37      book(_c["MCDR56"],     "_MCDR56");
 38      book(_c["MCDR84"],     "_MCDR84");
 39      book(_c["MCDR120"],    "_MCDR120");
 40      book(_c["MCDPhi56"],   "_MCDPhi56");
 41      book(_c["MCDPhi84"],   "_MCDPhi84");
 42      book(_c["MCDPhi120"], "_MCDPhi120");
 43    }
 44
 45
 46    /// Perform the per-event analysis
 47    void analyze(const Event& event) {
 48      const double weight = 1.0;
 49
 50      const Jets& jets = apply<FastJets>(event,"Jets").jetsByPt();
 51      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 52
 53      // Find the leading jet pT and eta
 54      if (jets.size() == 0) vetoEvent;
 55      const double ljpT = jets[0].pT();
 56      const double ljeta = jets[0].eta();
 57      MSG_DEBUG("Leading jet pT / eta: " << ljpT << " / " << ljeta);
 58
 59      // Minimum requirement for event
 60      if (ljpT > 56*GeV && fabs(ljeta) < 3.0) {
 61        // Find B hadrons in event
 62        int nab = 0, nb = 0; //counters for all B and independent B hadrons
 63        double etaB1 = 7.7, etaB2 = 7.7;
 64        double phiB1 = 7.7, phiB2 = 7.7;
 65        double pTB1 = 7.7, pTB2 = 7.7;
 66
 67        for (const Particle& p : ufs.particles()) {
 68          int aid = p.abspid();
 69          if (aid/100 == 5 || aid/1000==5) {
 70            nab++;
 71            // 2J+1 == 1 (mesons) or 2 (baryons)
 72            if (aid%10 == 1 || aid%10 == 2) {
 73              // No B decaying to B
 74              if (aid != 5222 && aid != 5112 && aid != 5212 && aid != 5322) {
 75                if (nb==0) {
 76                  etaB1 = p.eta();
 77                  phiB1 = p.phi();
 78                  pTB1 = p.pT();
 79                } else if (nb==1) {
 80                  etaB2 = p.eta();
 81                  phiB2 = p.phi();
 82                  pTB2 = p.pT();
 83                }
 84                nb++;
 85              }
 86            }
 87            MSG_DEBUG("ID " << aid <<  " B hadron");
 88          }
 89        }
 90
 91        if (nb==2 && pTB1 > 15*GeV && pTB2 > 15*GeV && fabs(etaB1) < 2.0 && fabs(etaB2) < 2.0) {
 92          double dPhi = deltaPhi(phiB1, phiB2);
 93          double dR = deltaR(etaB1, phiB1, etaB2, phiB2);
 94          MSG_DEBUG("DR/DPhi " << dR << " " << dPhi);
 95
 96          // MC counters
 97          if (dR > 2.4) _c["MCDR56"]->fill();
 98          if (dR > 2.4 && ljpT > 84*GeV) _c["MCDR84"]->fill();
 99          if (dR > 2.4 && ljpT > 120*GeV) _c["MCDR120"]->fill();
100          if (dPhi > 3.*PI/4.) _c["MCDPhi56"]->fill();
101          if (dPhi > 3.*PI/4. && ljpT > 84*GeV) _c["MCDPhi84"]->fill();
102          if (dPhi > 3.*PI/4. && ljpT > 120*GeV) _c["MCDPhi120"]->fill();
103
104          _h_dsigma_dR_56GeV->fill(dR, weight);
105          if (ljpT > 84*GeV) _h_dsigma_dR_84GeV->fill(dR, weight);
106          if (ljpT > 120*GeV) _h_dsigma_dR_120GeV->fill(dR, weight);
107          _h_dsigma_dPhi_56GeV->fill(dPhi, weight);
108          if (ljpT > 84*GeV) _h_dsigma_dPhi_84GeV->fill(dPhi, weight);
109          if (ljpT > 120*GeV) _h_dsigma_dPhi_120GeV->fill(dPhi, weight);
110          //MSG_DEBUG("nb " << nb << " " << nab);
111        }
112      }
113    }
114
115
116    /// Normalise histograms etc., after the run
117    void finalize() {
118      MSG_DEBUG("crossSection " << crossSection() << " sumOfWeights " << sumOfWeights());
119
120      // Hardcoded bin widths
121      double DRbin = 0.4;
122      double DPhibin = PI/8.0;
123      // Find out the correct numbers
124      double nDataDR56 = 25862.20;
125      double nDataDR84 = 5675.55;
126      double nDataDR120 = 1042.72;
127      double nDataDPhi56 = 24220.00;
128      double nDataDPhi84 = 4964.00;
129      double nDataDPhi120 = 919.10;
130      double normDR56 = safediv(nDataDR56, dbl(*_c["MCDR56"]), crossSection()/sumOfWeights());
131      double normDR84 = safediv(nDataDR84, dbl(*_c["MCDR84"]), crossSection()/sumOfWeights());
132      double normDR120 = safediv(nDataDR120, dbl(*_c["MCDR120"]), crossSection()/sumOfWeights());
133      double normDPhi56 = safediv(nDataDPhi56, dbl(*_c["MCDPhi56"]), crossSection()/sumOfWeights());
134      double normDPhi84 = safediv(nDataDPhi84, dbl(*_c["MCDPhi84"]), crossSection()/sumOfWeights());
135      double normDPhi120 = safediv(nDataDPhi120, dbl(*_c["MCDPhi120"]), crossSection()/sumOfWeights());
136      scale(_h_dsigma_dR_56GeV, normDR56*DRbin);
137      scale(_h_dsigma_dR_84GeV, normDR84*DRbin);
138      scale(_h_dsigma_dR_120GeV, normDR120*DRbin);
139      scale(_h_dsigma_dPhi_56GeV, normDPhi56*DPhibin);
140      scale(_h_dsigma_dPhi_84GeV, normDPhi84*DPhibin);
141      scale(_h_dsigma_dPhi_120GeV, normDPhi120*DPhibin);
142    }
143
144    /// @}
145
146
147  private:
148
149    /// Counters
150    map<string, CounterPtr> _c;
151
152    /// @name Histograms
153    /// @{
154    Histo1DPtr _h_dsigma_dR_56GeV, _h_dsigma_dR_84GeV, _h_dsigma_dR_120GeV;
155    Histo1DPtr _h_dsigma_dPhi_56GeV, _h_dsigma_dPhi_84GeV, _h_dsigma_dPhi_120GeV;
156    /// @}
157
158  };
159
160
161
162  RIVET_DECLARE_ALIASED_PLUGIN(CMS_2011_S8973270, CMS_2011_I889807);
163
164}