A measurement of the dijet production cross section is reported based on proton-proton collision data collected in 2016 at s = 13 Te V by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb - 1 . Jets are reconstructed with the anti- k T algorithm for distance parameters of R = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity | y | max of the two jets with the highest transverse momenta p T and their invariant mass m 1 , 2 , and triple-differentially (3D) as a function of the rapidity separation y ∗ , the total boost y b , and either m 1 , 2 or the average p T of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of α S ( m Z ) = 0.1179 ± 0.0019 .

• Publikační typ
• časopisecké články MeSH

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.

• Publikační typ
• časopisecké články MeSH

Events with no charged particles produced between the two leading jets are studied in proton-proton collisions at s = 7 TeV . The jets were required to have transverse momentum p T jet > 40 GeV and pseudorapidity 1.5 < | η jet | < 4.7 , and to have values of η jet with opposite signs. The data used for this study were collected with the CMS detector during low-luminosity running at the LHC, and correspond to an integrated luminosity of 8 pb - 1 . Events with no charged particles with p T > 0.2 GeV in the interval - 1 < η < 1 between the jets are observed in excess of calculations that assume no color-singlet exchange. The fraction of events with such a rapidity gap, amounting to 0.5-1% of the selected dijet sample, is measured as a function of the p T of the second-leading jet and of the rapidity separation between the jets. The data are compared to previous measurements at the Tevatron, and to perturbative quantum chromodynamics calculations based on the Balitsky-Fadin-Kuraev-Lipatov evolution equations, including different models of the non-perturbative gap survival probability.

• Klíčová slova
• CMS, Diffraction, Physics, QCD,
• Publikační typ
• časopisecké články MeSH