Linear vs non-linear QCD evolution: from HERA data to LHC phenomenology

TL;DR

This paper compares linear DGLAP and non-linear rcBK QCD evolution models using HERA data to determine their applicability and impact on LHC predictions, highlighting the regimes where non-linear effects are significant.

Contribution

It assesses the validity of the rcBK non-linear evolution equations against DGLAP fits and explores their implications for LHC phenomenology.

Findings

rcBK accurately describes data in specific small-x regions

DGLAP fits are less effective at very low x

Applying kinematic cuts influences LHC predictions

Abstract

The very precise combined HERA data provides a testing ground in which the relevance of novel QCD regimes, other than the successful linear DGLAP evolution, in small-x inclusive DIS data can be ascertained. We present a study of the dependence of the AAMQS fits, based on the running coupling BK non-linear evolution equations (rcBK), on the fitted dataset. This allows for the identification of the kinematical region where rcBK accurately describes the data, and thus for the determination of its applicability boundary. We compare the rcBK results with NNLO DGLAP fits, obtained with the NNPDF methodology with analogous kinematical cuts. Further, we explore the impact on LHC phenomenology of applying stringent kinematical cuts to the low-x HERA data in a DGLAP fit.