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Three-jet DIS final states from kt-dependent parton showers

F. Hautmann, H. Jung

TL;DR

The paper addresses large theoretical uncertainties in three-jet DIS final states at NLO by exploring parton-shower approaches that incorporate finite-$k_ot$ corrections through unintegrated PDFs and transverse-momentum dependent matrix elements. It compares NLO predictions with ZEUS data and demonstrates that k_perp-shower frameworks like Cascade better describe jet angular correlations, especially for small azimuthal separations, than standard collinear showers. The results highlight the importance of non-ordered initial-state radiation and high-energy factorization in accurately modeling multi-jet DIS, with implications for extrapolating these effects to LHC energies. Overall, the study provides a consistent parton-shower picture that improves agreement with data by going beyond strictly collinear initial-state evolution.

Abstract

Experimental measurements of angular correlations in three-jet final states have recently been performed in DIS. Next-to-leading-order QCD results for these observables are affected by large theoretical uncertainties in the kinematic region of the data. We discuss the effects of multiple QCD radiation at higher order using parton-shower methods based on transverse-momentum dependent parton distributions and matrix elements. We present Monte-Carlo results for azimuthal two-jet and three-jet distributions, and discuss the comparison with experimental data.

Three-jet DIS final states from kt-dependent parton showers

TL;DR

The paper addresses large theoretical uncertainties in three-jet DIS final states at NLO by exploring parton-shower approaches that incorporate finite- corrections through unintegrated PDFs and transverse-momentum dependent matrix elements. It compares NLO predictions with ZEUS data and demonstrates that k_perp-shower frameworks like Cascade better describe jet angular correlations, especially for small azimuthal separations, than standard collinear showers. The results highlight the importance of non-ordered initial-state radiation and high-energy factorization in accurately modeling multi-jet DIS, with implications for extrapolating these effects to LHC energies. Overall, the study provides a consistent parton-shower picture that improves agreement with data by going beyond strictly collinear initial-state evolution.

Abstract

Experimental measurements of angular correlations in three-jet final states have recently been performed in DIS. Next-to-leading-order QCD results for these observables are affected by large theoretical uncertainties in the kinematic region of the data. We discuss the effects of multiple QCD radiation at higher order using parton-shower methods based on transverse-momentum dependent parton distributions and matrix elements. We present Monte-Carlo results for azimuthal two-jet and three-jet distributions, and discuss the comparison with experimental data.

Paper Structure

This paper contains 2 sections, 3 figures.

Table of Contents

  1. Jet distributions from NLO calculations
  2. Parton showers with k$_\perp$-branching and jet correlations

Figures (3)

  • Figure 1: (left) Bjorken-x dependence and (right) azimuth dependence of di-jet distributions at HERA as measured by ZEUSzeus1931.
  • Figure 2: Angular jet correlations hj_ang obtained by Cascade and Herwig, compared with ZEUS data zeus1931: (left) di-jet cross section; (right) three-jet cross section.
  • Figure 3: Azimuthal distribution normalized to the back-to-back cross section hj_ang: (solid red) full result (u-pdf $\oplus$ ME); (dashed blue) no finite-k$_\perp$ correction in ME (u-pdf $\oplus$ ME$_{collin.}$); (dotted violet) u-pdf with no resolved branching.