Search

The modification of jet shapes in Pb-Pb collisions, relative to those in pp collisions, is studied for jets associated with an isolated photon. The data were collected with the CMS detector at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Jet shapes are constructed from charged particles with track transverse momenta (pT) above 1 GeV/c in annuli around the axes of jets with pjetT>30 GeV/c associated with an isolated photon with pγT>60 GeV/c. The jet shape distributions are consistent between peripheral Pb-Pb and pp collisions, but are modified for more central Pb-Pb collisions. In these central Pb-Pb events, a larger fraction of the jet momentum is observed at larger distances from the jet axis compared to pp, reflecting the interaction between the partonic medium created in heavy ion collisions and the traversing partons.

Measurements are presented of the triple-differential cross section for inclusive isolated-photon+jet events in pppp collisions at √s=8 TeV as a function of photon transverse momentum (pγT), photon pseudorapidity (ηγ), and jet pseudorapidity (ηjet). The data correspond to an integrated luminosity of 19.7fb−1 that probe a broad range of the available phase space, for |ηγ| 25GeV. The measurements are compared to next-to-leading order perturbative quantum chromodynamics calculations, which reproduce the data within uncertainties.

This Letter reports measurements of differential cross sections for the production of two Z bosons in association with jets in proton–proton collisions at √s=8 and 13 TeV. The analysis is based on data samples collected at the LHC with the CMS detector, corresponding to integrated luminosities of 19.7 and 35.9fb−1 at 8 and 13 TeV, respectively. The measurements are performed in the leptonic decay modes ZZ→ℓ+ℓ−ℓ′+ℓ′−, where ℓ,ℓ′=e,μ. The differential cross sections as a function of the jet multiplicity, the transverse momentum pT, and pseudorapidity of the pT -leading and subleading jets are presented. In addition, the differential cross sections as a function of variables sensitive to the vector boson scattering, such as the invariant mass of the two pT -leading jets and their pseudorapidity separation, are reported. The results are compared to theoretical predictions and found in good agreement within the theoretical and experimental uncertainties.

A measurement for inclusive 2- and 3-jet events of the azimuthal correlation between the two jets with the largest transverse momenta, Δφ12, is presented. The measurement considers events where the two leading jets are nearly collinear (“back-to-back”) in the transverse plane and is performed for several ranges of the leading jet transverse momentum. Proton-proton collision data collected with the CMS experiment at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 35.9 fb−1 are used. Predictions based on calculations using matrix elements at leading-order and next-to-leading-order accuracy in perturbative quantum chromodynamics supplemented with leading-log parton showers and hadronization are generally in agreement with the measurements. Discrepancies between the measurement and theoretical predictions are as large as 15%, mainly in the region 177º < Δφ12 < 180º. The 2- and 3-jet measurements are not simultaneously described by any of models.