Abstract
Collinear (small-angle) and large-angle, as well as soft and hard radiations are investigated in three-jet and {text {Z}} + two-jet events collected in proton-proton collisions at the LHC. The normalized production cross sections are measured as a function of the ratio of transverse momenta of two jets and their angular separation. The measurements in the three-jet and {text {Z}} + two-jet events are based on data collected at a center-of-mass energy of 8,{text {TeV}}, corresponding to an integrated luminosity of 19.8,text {fb}^{-1}. The {text {Z}} + two-jet events are reconstructed in the dimuon decay channel of the {text {Z}} boson. The three-jet measurement is extended to include sqrt{s} = 13,{text {TeV}} data corresponding to an integrated luminosity of 2.3,text {fb}^{-1}. The results are compared to predictions from event generators that include parton showers, multiple parton interactions, and hadronization. The collinear and soft regions are in general well described by parton showers, whereas the regions of large angular separation are often best described by calculations using higher-order matrix elements.
Highlights
Collimated streams of particles, produced in interactions of quarks and gluons and reconstructed as jets, are described by the theory of strong interactions, quantum chromodynamics (QCD)
The events with 0.3 < pT3/ pT2 < 0.6 are not used in the comparisons for the ΔR23 observable because we focus on the limits in soft and hard radiation
The data measurements are provided at the Durham High Energy Physics Database (HEPData) [48]
Summary
Collimated streams of particles, produced in interactions of quarks and gluons and reconstructed as jets, are described by the theory of strong interactions, quantum chromodynamics (QCD). (ii) small-angle (ΔR23 < 1.0) or large-angle (ΔR23 > 1.0) radiation, depending on the angular separation Δ R23 According to these classifications, events in the soft and small-angle radiation region, as shown, can only be described if soft gluon resummation, e.g., in form of a parton shower, is included, whereas events in the hard and. The measurements using three-jet final states are complementary to those with Z + two-jet events in a sense that different kinematic regions and initialstate flavor compositions are being probed. The goal of the measurements is: (i) to untangle the different features of the radiation in the collinear and large-angle events; (ii) to investigate how well the PS approach describes the hard and large-angle radiation patterns; and (iii) to illustrate how ME calculations can attempt to describe the soft and collinear regions
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