Two aspects of the Regge limit in QCD: Double Logs in Exclusive observables and Infrared Effects in Cross Sections

TL;DR

This paper explores two key aspects of the Regge limit in QCD: the use of BFKL formalism for phenomenology with new observables at the LHC, and the impact of infrared boundary conditions on the BFKL equation's structure and phenomenology.

Contribution

It introduces new observables for BFKL dynamics analysis at the LHC and studies how infrared boundary conditions alter the BFKL equation's structure and its phenomenological implications.

Findings

New multi-jet observables can signal BFKL dynamics at the LHC.

Infrared boundary conditions lead to a series of Regge poles in the BFKL equation.

Boundary conditions significantly affect intercepts and collinear regions.

Abstract

Two relevant points related to the application of the BFKL formalism to phenomenology are discussed. First, we have presented a set of observables characterizing multi-jet configurations event by event (average transverse momentum, average azimuthal angle, average ratio of jet rapidities) which can be used to find distinct signals of BFKL dynamics at the LHC. A numerical analysis has been shown using the Monte Carlo event generator BFKLex, modified to include higher-order collinear corrections in addition to the transverse-momentum implementation of the NLO kernel. We require to have two tagged forward/backward jets in the final state. Second, the structure of the BFKL equation changes if infrared boundary conditions are imposed when considering the running of the coupling. The cut in the complex angular momentum plane becomes an infinite series of Regge poles. Integrating along a contour off the real axis we find a strong dependence of the intercepts and collinear regions on the choice of the boundary conditions. The mean transverse scales dominant in the gluon ladder increase. This could have interesting phenomenological consequences.