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Determination of the strong coupling constant $α_s$ from transverse energy-energy correlations in multijet events at $\sqrt{s} = 8$ TeV using the ATLAS detector

ATLAS Collaboration

TL;DR

Measurements of transverse energy–energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented and the value of the strong coupling constant is extracted for different energy regimes.

Abstract

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to $\sqrt{s} = 8$ TeV proton-proton collisions with an integrated luminosity of 20.2 fb$^{-1}$. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of $α_s(μ)$ predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields $α_s(m_Z) = 0.1162 \pm 0.0011 \mbox{ (exp.)}^{+0.0084}_{-0.0070} \mbox{ (theo.)}$, while a global fit to the asymmetry distributions yields a value of $α_s(m_Z) = 0.1196 \pm 0.0013 \mbox{ (exp.)}^{+0.0075}_{-0.0045} \mbox{ (theo.)}$.

Determination of the strong coupling constant $α_s$ from transverse energy-energy correlations in multijet events at $\sqrt{s} = 8$ TeV using the ATLAS detector

TL;DR

Measurements of transverse energy–energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented and the value of the strong coupling constant is extracted for different energy regimes.

Abstract

Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to TeV proton-proton collisions with an integrated luminosity of 20.2 fb. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields , while a global fit to the asymmetry distributions yields a value of .

Paper Structure

This paper contains 18 sections, 11 equations, 11 figures, 13 tables.

Table of Contents

  1. Introduction
  2. ATLAS detector
  3. Monte Carlo simulation
  4. Data sample and jet calibration
  5. Results at the detector level
  6. Correction to particle level
  7. Systematic uncertainties
  8. Experimental results
  9. Theoretical predictions
  10. Non-perturbative corrections
  11. Theoretical uncertainties
  12. Comparison of theoretical predictions and experimental results
  13. Determination of $\alpha_{\mathrm{s}}$ and test of asymptotic freedom
  14. Fits to individual TEEC functions
  15. Global TEEC fit
  16. ...and 3 more sections

Figures (11)

  • Figure 1: Detector-level distributions for the TEEC (top) and ATEEC functions (bottom) for the first and the last $H_{\mathrm{T}2}$ intervals chosen in this analysis, together with MC predictions from Pythia8, Herwig++ and Sherpa. The total uncertainty, including statistical and detector experimental sources, i.e. those not related to unfolding corrections, is also indicated using an error bar for the distributions and a green-shaded band for the ratios. The systematic uncertainties are discussed in Section \ref{['sec:systematics']}.
  • Figure 2: Systematic uncertainties in the measured TEEC (top) and ATEEC distributions (bottom) for the first and the last bins in $H_{\mathrm{T}2}$. The total uncertainty is below 5% in all bins of the TEEC distributions.
  • Figure 3: Particle-level distributions for the TEEC functions in each of the $H_{\mathrm{T}2}$ intervals chosen in this analysis, together with MC predictions from Pythia8, Herwig++ and Sherpa. The total uncertainty, including statistical and other experimental sources is also indicated using an error bar for the distributions and a green-shaded band for the ratios.
  • Figure 4: Particle-level distributions for the ATEEC functions in each of the $H_{\mathrm{T}2}$ intervals chosen in this analysis, together with MC predictions from Pythia8, Herwig++ and Sherpa. The total uncertainty, including statistical and other experimental sources is also indicated using an error bar for the distributions and a green-shaded band for the ratios.
  • Figure 5: Non-perturbative correction factors for TEEC in the first and last bins of $H_{\mathrm{T}2}$ as a function of $\cos\phi$.
  • ...and 6 more figures