Rivet analyses

title: CMS_2024_I2780732

Measurement of Rdphi observable for the determination of the strong coupling at 13 TeV

Experiment: CMS (LHC)

Inspire ID: 2780732

Status: VALIDATED

Authors: - Paris Gianneios

References: - Expt page: CMS-SMP-22-005 - arXiv: 2404.16082

Beams: p+ p+

Beam energies: (6500.0, 6500.0)GeV

Run details: - pp to jets at $\sqrt(s) = 13$ TeV. Data collected by the CMS experiment during 2016, 2017 and 2018.

A measurement is presented of the ratio observable $R_{\Delta\phi}(p_\mathrm{T})$ that provides a measure of the azimuthal correlations among jets with large transverse momentum $p_\mathrm{T}$. The $R_{\Delta\phi}(p_\mathrm{T})$ variable is measured in multijet events over the $p_\mathrm{T} = 360\mathord{-}3170~\mathrm{GeV}$ range based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $134~\mathrm{fb}^{-1}$. The results are compared with predictions from Monte Carlo parton-shower event generator simulations, as well as with fixed-order perturbative quantum chromodynamics (pQCD) predictions at next-to-leading-order (NLO) accuracy obtained with different parton distribution functions (PDFs) and corrected for nonperturbative and electroweak effects. Data and theory agree within uncertainties. From the comparison of the measured distribution with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling constant at the Z boson mass scale is $\alpha_{\text{S}}(m_\text{Z}) = 0.1177 \pm 0.0013\, \text{(exp)} {-0.0073}^{+0.0116} \, \text{(theo)} = 0.1177{-0.0074}^{+0.0117}$, where the total uncertainty is dominated by the scale dependence of the fixed-order predictions. A test of the running of $\alpha_S(Q)$ in the TeV region shows no deviation from the expected NLO pQCD behaviour.

Source code:CMS_2024_I2780732.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// @brief Rdphi observable for the determination of the strong coupling at 13 TeV class CMS_2024_I2780732 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2024_I2780732);

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  FinalState fs;
  FastJets akt(fs, JetAlg::ANTIKT, 0.7);
  declare(akt, "antikT");

  // Book histograms
  // Denominator and numerator of Rdphi observable
  book(_h_Inclusive_Denominator, "_Inclusive_Denominator", refData(2, 1, 1));
  book(_h_Dphi_Numerator, "_Inclusive_Numerator", refData(2, 1, 1));
  book(_h_Rdphi, 2, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  // Select jets with pt > 50 GeV and absolute rapidity < 2.5
  const Jets& jets = apply<FastJets>(event, "antikT")
                         .jetsByPt(Cuts::absrap < 2.5 && Cuts::pT > 50. * GeV);

  // Loop over all jets and fill the denominator (inclusive jets)
  for (unsigned int i = 0; i < jets.size(); ++i) {
    _h_Inclusive_Denominator->fill(jets[i].pT() / GeV);

    // Loop looking for neighboring jets for each jet
    for (unsigned int j = 0; j < jets.size(); ++j) {
      if (i == j) continue;
      const double dphi = deltaPhi(jets[i], jets[j]);

      // Select neighboring jets and fill the numerator
      if ((dphi > 2. * pi / 3.) && (dphi < 7. * pi / 8.) && (jets[j].pT() > 100. * GeV)) {
        _h_Dphi_Numerator->fill(jets[i].pT() / GeV);
      }
    }
  }
}


/// Calculation of Rdphi observable
void finalize() {

  divide(_h_Dphi_Numerator, _h_Inclusive_Denominator, _h_Rdphi);
}


/// @name Histograms
Histo1DPtr _h_Dphi_Numerator, _h_Inclusive_Denominator;
Estimate1DPtr _h_Rdphi;

};

RIVET_DECLARE_PLUGIN(CMS_2024_I2780732);

} ```