Hunting BFKL in semi-hard reactions at the LHC

TL;DR

This paper compares BFKL resummation and fixed-order calculations for semi-hard processes at the LHC, demonstrating how to distinguish between these approaches using specific observables and kinematic configurations.

Contribution

It provides the first comprehensive next-to-leading logarithmic analysis of semi-hard LHC processes, highlighting discriminative observables and introducing the JETHAD computational tool.

Findings

Resummed and fixed-order predictions can be clearly discriminated in specific kinematic ranges.

Scale optimization and PDF/FF uncertainties are systematically addressed.

The JETHAD tool facilitates calculations of semi-hard reactions.

Abstract

The agreement between calculations inspired by the resummation of energy logarithms, known as BFKL approach, and experimental data in the semi-hard sector of QCD has become manifest after a wealthy series of phenomenological analyses. However, the contingency that the same data could be concurrently portrayed at the hand of fixed-order, DGLAP-based calculations, has been pointed out recently, but not yet punctually addressed. Taking advantage of the richness of configurations gained by combining the acceptances of CMS and CASTOR detectors, we give results in the full next-to-leading logarithmic approximation of cross sections, azimuthal correlations and azimuthal distributions for three distinct semi-hard processes, each of them featuring a peculiar final-state exclusiveness. Then, making use of disjoint intervals for the transverse momenta of the emitted objects, i.e. $\kappa$-windows, we clearly highlight how high-energy resummed and fixed-order driven predictions for semi-hard sensitive observables can be decisively discriminated in the kinematic ranges typical of current and forthcoming analyses at the LHC. The scale-optimization issue is also introduced and explored, while the uncertainty coming from the use of different PDF and FF set is deservedly handled. Finally, a brief overview of JETHAD, a numerical tool recently developed, suited for the computation of inclusive semi-hard reactions is provided.