Abstract
A measurement of the rapidity and transverse momentum dependence of dijet azimuthal decorrelations is presented, using the quantity $R_{\Delta \phi}$. The quantity $R_{\Delta \phi}$ specifies the fraction of the inclusive dijet events in which the azimuthal opening angle of the two jets with the highest transverse momenta is less than a given value of the parameter $\Delta \phi_\mathrm{max}$. The quantity $R_{\Delta \phi}$ is measured in proton--proton collisions at $\sqrt{s}=$8 TeV as a function of the dijet rapidity interval, the event total scalar transverse momentum, and $\Delta \phi_\mathrm{max}$. The measurement uses an event sample corresponding to an integrated luminosity of 20.2 fb$^{-1}$ collected with the ATLAS detector at the CERN Large Hadron Collider. Predictions of a perturbative QCD calculation at next-to-leading order in the strong coupling with corrections for non-perturbative effects are compared to the data. The theoretical predictions describe the data in the whole kinematic region. The data are used to determine the strong coupling $\alpha_{\mathrm{S}}$ and to study its running for momentum transfers from 260 GeV to above 1.6 TeV. An analysis that combines data at all momentum transfers results in $\alpha_{\mathrm{S}}(m_{Z}) = 0.1127^{+0.0063}_{-0.0027}$.
Highlights
In high-energy particle collisions, measurements of the production rates of hadronic jets with large transverse momentum pT relative to the beam direction can be employed to test the predictions of perturbative quantum chromodynamics
The most precise αSðmZÞ result from hadron collision data is αSðmZÞ 1⁄4 0.1161þ−00..00004481 [9], obtained from inclusive jet cross-section data, using perturbative quantum chromodynamics (pQCD) predictions beyond the next-to-leading order (NLO)
Theoretical predictions based on NLO pQCD or LO with corrections for nonperturbative effects, as described in Sec
Summary
In high-energy particle collisions, measurements of the production rates of hadronic jets with large transverse momentum pT relative to the beam direction can be employed to test the predictions of perturbative quantum chromodynamics (pQCD). The results can be used to determine the strong coupling αS, and to test the pQCD predictions for the dependence of αS on the momentum transfer Q (the “running” of αS) by the renormalization group equation (RGE) [1,2]. Recent αS results from hadron collisions are limited by theoretical uncertainties related to the scale dependence of the fixed-order pQCD calculations. The most precise αSðmZÞ result from hadron collision data is αSðmZÞ 1⁄4 0.1161þ−00..00004481 [9], obtained from inclusive jet cross-section data, using pQCD predictions beyond the next-to-leading order (NLO).
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