A measurement is presented of a ratio observable that provides a measure of the azimuthal correlations among jets with large transverse momentum p T . This observable is measured in multijet events over the range of p T = 360 - 3170 Ge V based on data collected by the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 Te V , corresponding to an integrated luminosity of 134 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 observable with the pQCD prediction obtained with the NNPDF3.1 NLO PDFs, the strong coupling at the Z boson mass scale is α S ( m Z ) = 0.1177 ± 0.0013 (exp) - 0.0073 + 0.0116 (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 α S in the Te V region shows no deviation from the expected NLO pQCD behaviour.

• Publication type
• Journal Article MeSH

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 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 ± 0.0011 (exp.) - 0.0070 + 0.0084 (theo.) , while a global fit to the asymmetry distributions yields a value of α s ( m Z ) = 0.1196 ± 0.0013 (exp.) - 0.0045 + 0.0075 (theo.) .

• Publication type
• Journal Article MeSH

A measurement is presented of the triple-differential dijet cross section at a centre-of-mass energy of 8 TeV using 19.7 fb -1 of data collected with the CMS detector in proton-proton collisions at the LHC. The cross section is measured as a function of the average transverse momentum, half the rapidity separation, and the boost of the two leading jets in the event. The cross section is corrected for detector effects and compared to calculations in perturbative quantum chromodynamics at next-to-leading order accuracy, complemented with electroweak and nonperturbative corrections. New constraints on parton distribution functions are obtained and the inferred value of the strong coupling constant is α S ( M Z ) = 0.1199 ± 0.0015 ( exp ) - 0.0020 + 0.0031 ( theo ) , where M Z is the mass of the Z boson.

• Keywords
• CMS, Jets, PDF, Physics, QCD, Strong coupling constant, alpha-s,
• Publication type
• Journal Article MeSH