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Measurement of transverse energy-energy correlations in multi-jet events in $pp$ collisions at $\sqrt{s} = 7$ TeV using the ATLAS detector and determination of the strong coupling constant $α_{\mathrm{s}}(m_Z)$

ATLAS Collaboration

TL;DR

Using 158 pb^-1 of ATLAS 7 TeV data, TEEC and ATEEC are measured in multi-jet events and unfolded to particle level for comparison with NLO pQCD. The analysis yields αs(mZ) determinations from TEEC and ATEEC with CT10 PDFs, finding αs(mZ) ≈ 0.1173 (TEEC) and αs(mZ) ≈ 0.1195 (ATEEC), with scale uncertainties dominating. The results agree with the world average and demonstrate the sensitivity of energy–energy correlations to the strong coupling, while highlighting the need for higher-order calculations to reduce theory uncertainties. Overall, the study provides a robust perturbative QCD test at large momentum transfers and informs future precision determinations of αs.

Abstract

High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy-energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 $\mathrm{pb}^{-1}$. The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next-to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the $Z$ boson mass is determined to be $α_{\mathrm{s}}(m_Z) = 0.1173 \pm 0.0010 \mbox{ (exp.) }^{+0.0065}_{-0.0026} \mbox{ (theo.)}$.

Measurement of transverse energy-energy correlations in multi-jet events in $pp$ collisions at $\sqrt{s} = 7$ TeV using the ATLAS detector and determination of the strong coupling constant $α_{\mathrm{s}}(m_Z)$

TL;DR

Using 158 pb^-1 of ATLAS 7 TeV data, TEEC and ATEEC are measured in multi-jet events and unfolded to particle level for comparison with NLO pQCD. The analysis yields αs(mZ) determinations from TEEC and ATEEC with CT10 PDFs, finding αs(mZ) ≈ 0.1173 (TEEC) and αs(mZ) ≈ 0.1195 (ATEEC), with scale uncertainties dominating. The results agree with the world average and demonstrate the sensitivity of energy–energy correlations to the strong coupling, while highlighting the need for higher-order calculations to reduce theory uncertainties. Overall, the study provides a robust perturbative QCD test at large momentum transfers and informs future precision determinations of αs.

Abstract

High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energy-energy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 . The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at next-to-leading-order accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the boson mass is determined to be .

Paper Structure

This paper contains 10 sections, 10 equations, 4 figures, 4 tables.

Table of Contents

  1. Introduction
  2. The ATLAS detector
  3. Monte Carlo samples
  4. Event selection and jet calibration
  5. Results at the detector level
  6. Correction to particle level
  7. Theoretical predictions and uncertainties
  8. Determination of the strong coupling $\alpha_{\mathrm{s}}(m_\Zboson)$
  9. Summary
  10. Acknowledgements

Figures (4)

  • Figure 1:
  • Figure 2: Relative systematic uncertainties for the TEEC (left) and the ATEEC (right) as a function of $\cos\phi$.
  • Figure 3: The unfolded distributions for transverse energy--energy correlation (left) and its asymmetry (right) along with comparisons to MC expectations. The statistical uncertainties are shown with error bars, while the total experimental uncertainties are shown in a shaded band.
  • Figure 4: The unfolded distributions for transverse energy--energy correlation (left) and its asymmetry (right) compared with the results of a fit to pQCD NLO calculations including non-perturbative corrections. The green shaded band indicates the uncertainty on the theoretical predictions, which includes the sum in quadrature of uncertainties associated with scale, $\alpha_s$, PDF and NPC. The statistical uncertainties on the predictions are indicated by green error bars, appreciable only on the tail of the ATEEC. The solid error bars on the data points (in black) indicate the experimental uncertainties taking into account the correlations between them. The fitted values of the strong coupling constant are $\alpha^{\mathrm{fit}}_{\mathrm{s}}(m_\Zboson) = 0.1173$ (TEEC) and $\alpha^{\mathrm{fit}}_{\mathrm{s}}(m_\Zboson) = 0.1195$ (ATEEC).