Rivet analyses

title: CMS_2012_I1184941

Measurement of the differential cross section for inclusive dijet production as a function of $\xi$ in 7 TeV proton-proton collisions.

Experiment: CMS (LHC)

Inspire ID: 1184941

Status: VALIDATED

Authors: - Sercan Sen - Alexander Proskuryakov

References: - arXiv: 1209.1805 - Submitted to Phys. Rev. D

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - High statistics is needed to observe events in the lowest (xi) bin. Distributions are presented for hard QCD events (i.e. with $\hat{\pT}$ greater than 15 GeV) and diffractive-enhanced events.

Measurement of the differential cross section for inclusive dijet production as a function of $\xi$ which approximates the fractional momentum loss of the scattered proton in single-diffraction events. The data used has a total integrated luminosity of 2.7 nb$^{-1}$ collected during 2010 with low instantaneous luminosity. Events are selected with at least two jets in $|\eta| < 4.4$ with $\pT > 20$ GeV and all final states particles are used for the reconstruction of $\xi$.

Source code:CMS_2012_I1184941.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

class CMS_2012_I1184941 : public Analysis { public:

CMS_2012_I1184941()
    : Analysis("CMS_2012_I1184941") { }


void init() {
  FinalState fs;
  declare(fs, "FS");

  const FastJets jets(FinalState((Cuts::etaIn(-4.9, 4.9))), JetAlg::ANTIKT, 0.5);
  declare(jets, "AntiKtJets05");

  book(_h_xi, 1, 1, 1);
}


void analyze(const Event& event) {
  double xiM = 0.;
  double xiP = 0.;

  const Jets jets = apply<FastJets>(event, "AntiKtJets05").jetsByPt(Cuts::pT > 20. * GeV);
  if (jets.size() < 2) vetoEvent; // require a dijet system with a 20 GeV cut on both jets
  if (fabs(jets[0].eta()) > 4.4 || fabs(jets[1].eta()) > 4.4) vetoEvent;

  const FinalState& fsp = apply<FinalState>(event, "FS");

  for (const Particle& p : fsp.particles(cmpMomByEta)) {
    const double eta = p.eta();
    const double energy = p.E();
    const double costheta = cos(p.theta());
    // Yes, they really correct to +/- infinity, using Pythia 8 ...
    if (eta < 4.9) xiP += (energy + energy * costheta);
    if (eta > -4.9) xiM += (energy - energy * costheta);
  }

  xiP = xiP / (sqrtS() / GeV);
  xiM = xiM / (sqrtS() / GeV);

  _h_xi->fill(xiM); // Fill the histogram both with xiP and xiM, and get the average in the endjob.
  _h_xi->fill(xiP);
}


void finalize() {
  scale(_h_xi, crossSection() / microbarn / sumOfWeights() / 2.);
}

private:

Histo1DPtr _h_xi;

};

RIVET_DECLARE_PLUGIN(CMS_2012_I1184941);

} ```