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

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.) .

• Publikační typ
• časopisecké články MeSH