Abstract
Several characteristics of jet production in pp collisions have been measured by the ATLAS and CMS collaborations at the LHC. Measurements of event shapes and multi-jet production probe the dynamics of QCD in the soft regime and can constrain parton shower and hadronisation models. Measurements of multi-jet systems with a veto on additional jets probe QCD radiation effects. Double-differential cross-sections for threeand four-jet final states are measured at different centre-of-mass energies of pp collisions and are compared to expectations based on NLO QCD calculations. The distribution of the jet charge has been measured in di-jet events and compared to predictions from different hadronisation models and tunes. Jet-jet energy correlations are sensitive to the strong coupling constant. These measurements constitute precision tests of QCD in a new energy regime.
Highlights
Jets are narrow collimated clusters of stable particles produced in high-energy particle interactions
This paper presents several studies [3,4,5,6,7,8,9,10,11] of jet production ae-mail: nuno.anjos@cern.ch bWork supported by the Beatriu de Pinós program managed by Agència de Gestió d’Ajuts Universitaris i de Recerca with the support of the Secretaria d’Universitats i Recerca of the Departament d’Economia i Coneixement of the Generalitat de Catalunya, and the Cofund program of the Marie Curie Actions of the 7th R&D Framework Program of the European Union
Fixed order computations provide a good description of jet production, for certain observables and in some regions of the phase space higher-order contributions are important and must be resummed to all orders. This is the case for di-jet events with large rapidity separation between the two jets, Δy, and/or when a veto is applied on additional jets with partons with high-transverse momentum (pT) > Q0 produced in the rapidity interval between them; Q0 is called a veto scale
Summary
Jets are narrow collimated clusters of stable particles (mainly hadrons) produced in high-energy particle interactions. Partons evolve from hard to soft scales by a process of emission of additional gluons and production of quark-antiquark pairs, known as the parton shower (PS). This phase can be described by perturbative QCD (pQCD) approximations. The PF algorithm utilizes the best energy measurements of each particle candidate from the most suitable combination of detector components Both experiments use the anti-kT [14] algorithm as implemented in the FastJet [15] package to reconstruct jets. The values of the jet distance parameter R used by ATLAS are 0.4 and 0.6, while CMS uses 0.5 and 0.7 Both experiments apply a factorized jet calibration procedure with corrections for pile-up and jet energy scale. The Powheg framework [21,22,23] provides a full next-to-leading-order (NLO) di-jet calculation accounting for the emission of an additional third hard parton, and can be matched to a PS MC
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