Trijets in $$k_\mathrm{T}$$kT -factorisation: matrix elements vs parton shower
- PDF / 608,932 Bytes
- 9 Pages / 595.276 x 790.866 pts Page_size
- 44 Downloads / 159 Views
Regular Article - Theoretical Physics
Trijets in kT -factorisation: matrix elements vs parton shower H. Van Haevermaet1, A. Van Hameren2 , P. Kotko3 , K. Kutak2,a , P. Van Mechelen1 1
Particle Physics Group, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium Polish Academy of Sciences, Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Kraków, Poland 3 Physics Faculty, AGH University of Science and Technology, Mickiewicza 30, 30-059 Kraków, Poland
2
Received: 24 April 2020 / Accepted: 27 June 2020 © The Author(s) 2020
Abstract We study 3-jet event topologies in proton-proton √ collisions at a centre-of-mass energy of s = 13 TeV in a configuration, where one jet is present in the central pseudorapidity region (|η| < 2.0) while two other jets are in a more forward (same hemisphere) area (|η| > 2.0). We compare various parton level predictions using: collinear factorisation, kT -factorisation with fully off-shell matrix elements and the hybrid framework. We study the influence of different parton distribution functions, initial state radiation, final state radiation, and hadronisation. We focus on differential cross sections as a function of azimuthal angle difference between the leading dijet system and the third jet, which is found to have excellent sensitivity to the physical effects under study.
1 Introduction Thanks to the hadron–parton duality, jet production processes at the Large Hadron Collider (LHC) are the best tools to study perturbative Quantum Chromodynamics (QCD) (for a review see [1]). The relation between experimental observables and the QCD degrees of freedom is, however, highly nontrivial: due to colour confinement, the partonic content of hadrons is unknown from first principles, while asymptotic freedom of quarks and gluons allows to study many aspects of hadronic physics perturbatively [2]. So-called factorisation theorems make this relation formal and allow for a systematic approach. In the case of some of the simplest observables, like hadron structure functions or the cross section for inclusive production of very energetic jets, a suitable, well established formalism is provided by the so-called collinear factorisation theorem (for a review see [2]). Using it, the cross sections for sufficiently inclusive processes can be calculated in terms of collinear Parton Distribution Functions (PDFs) and perturbative on-shell amplitudes for the scattering of quarks and gluons. Less inclusive observables, or processes involving a e-mail:
multiple large scales, however, require different formalisms utilising various all-order resummations of potentially large logarithms. At the LHC, many jet observables are subject to resummation and other corrections reaching beyond collinear factorisation (e.g. multiple partonic interactions). Among other reasons, this is due to the overall very large centre-ofmass energy, as well as the ability to measure small jet transverse momenta, pT , with good resolution. In addition, good jet reconstruction capabilities allow to measure the azimuth
Data Loading...
