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Phenomenology of jet physics in the BFKL formalism at NLO

Florian Schwennsen

TL;DR

This work develops a comprehensive NLO BFKL framework for jet production in high-energy QCD, constructing a central-rapidity jet vertex within $k_T$-factorization and defining an NLO unintegrated gluon density for small-$x$ hadron collisions. It provides a careful separation of MRK and QMRK, analyzes energy-scale dependencies, and applies resummation techniques to stabilize the NLO kernel, enabling more reliable predictions for jet observables and Mueller–Navelet decorrelations. The study extends to forward jets in ep scattering, deriving leptonic and jet-vertex contributions and delivering predictions under experimental cuts. Overall, the results offer a path toward fully NLO, $k_T$-factorized jet phenomenology at the LHC, with implications for multi-jet processes and high-energy QCD dynamics.

Abstract

We study jet physics in the high energy regime of QCD. Based on the NLO BFKL equation, we construct a vertex for the production of a jet at central rapidity in k_T-factorization. A jet algorithm is introduced, and we take special care of the separation of multi-Regge and quasi-multi-Regge kinematics. The connection with the energy scale of the evolution is investigated in detail. The result is discussed for two situations: scattering of highly virtual photons, which requires a symmetric energy scale to separate the impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed. For the second case we are able to define a NLO unintegrated gluon density, valid in the small-x regime, and give the evolution equation for this density as well. In the second part, we examine the angular decorrelation of Mueller-Navelet jets. Using an operator formalism in the space of anomalous dimension and conformal spin, we implement the NLO BFKL Green's function to study the rapidity dependence of angular decorrelations. We incorporate the necessary summation of collinearly enhanced corrections beyond NLO accuracy. We compare our results with data from the Tevatron ppbar-collider and provide predictions for the LHC as well. We also extend our study to the angular decorrelation between a forward jets and the electron in deep inelastic ep scattering. The angular decorrelation has not been measured in DIS so far, but we give theoretical results for this observable which already implement the experimental cuts.

Phenomenology of jet physics in the BFKL formalism at NLO

TL;DR

This work develops a comprehensive NLO BFKL framework for jet production in high-energy QCD, constructing a central-rapidity jet vertex within -factorization and defining an NLO unintegrated gluon density for small- hadron collisions. It provides a careful separation of MRK and QMRK, analyzes energy-scale dependencies, and applies resummation techniques to stabilize the NLO kernel, enabling more reliable predictions for jet observables and Mueller–Navelet decorrelations. The study extends to forward jets in ep scattering, deriving leptonic and jet-vertex contributions and delivering predictions under experimental cuts. Overall, the results offer a path toward fully NLO, -factorized jet phenomenology at the LHC, with implications for multi-jet processes and high-energy QCD dynamics.

Abstract

We study jet physics in the high energy regime of QCD. Based on the NLO BFKL equation, we construct a vertex for the production of a jet at central rapidity in k_T-factorization. A jet algorithm is introduced, and we take special care of the separation of multi-Regge and quasi-multi-Regge kinematics. The connection with the energy scale of the evolution is investigated in detail. The result is discussed for two situations: scattering of highly virtual photons, which requires a symmetric energy scale to separate the impact factors from the gluon Green's function, and hadron-hadron collisions, where a non-symmetric scale choice is needed. For the second case we are able to define a NLO unintegrated gluon density, valid in the small-x regime, and give the evolution equation for this density as well. In the second part, we examine the angular decorrelation of Mueller-Navelet jets. Using an operator formalism in the space of anomalous dimension and conformal spin, we implement the NLO BFKL Green's function to study the rapidity dependence of angular decorrelations. We incorporate the necessary summation of collinearly enhanced corrections beyond NLO accuracy. We compare our results with data from the Tevatron ppbar-collider and provide predictions for the LHC as well. We also extend our study to the angular decorrelation between a forward jets and the electron in deep inelastic ep scattering. The angular decorrelation has not been measured in DIS so far, but we give theoretical results for this observable which already implement the experimental cuts.

Paper Structure

This paper contains 34 sections, 203 equations, 25 figures.

Table of Contents

  1. Introduction
  2. BFKL equation
  3. BFKL equation at LO
  4. Different contributions at NLO
  5. Properties of the NLO BFKL kernel and resummation of terms beyond NLO
  6. The LO kernel and its eigenfunctions
  7. The NLO kernel
  8. Phenomenology
  9. Jet production
  10. Inclusive jet production at LO
  11. Inclusive jet production at NLO
  12. The NLO jet vertex
  13. Production of jets in $\gamma^*\gamma^*$ scattering
  14. The unintegrated gluon density and jet production in hadron--hadron collisions
  15. Cancellation of divergences and a closer look at the separation between MRK and QMRK
  16. ...and 19 more sections

Figures (25)

  • Figure 1: Notation for particle production in MRK.
  • Figure 2: Contributions to real emission kernel at LO (a) and NLO (b-e).
  • Figure 3: LO kernel for conformal spin $n=0$ at a scale $\mu=30$GeV.
  • Figure 4: NLO kernel for conformal spin $n=0$ at a scale $\mu=30$GeV.
  • Figure 5: Resummed kernel (scheme 3) for conformal spin $n=0$ at a scale $\mu=30$GeV.
  • ...and 20 more figures