How to fit PDFs in the presence of new physics?

TL;DR

This paper explores how global PDF fits at the LHC can mask signs of new physics in high-energy data, proposing methods to identify and disentangle such effects to improve interpretation accuracy.

Contribution

It introduces a methodology to detect when PDF fits might absorb new physics signals and discusses strategies for simultaneous fitting of PDFs and new physics effects.

Findings

PDF fits can completely absorb new physics signals in high-energy tails

Strategies to distinguish between PDF effects and genuine new physics signals

Highlighting the importance of combined high-luminosity and low-energy measurements

Abstract

The interpretation of LHC data, and the assessment of possible hints of new physics, require the precise knowledge of the proton structure in terms of parton distribution functions (PDFs). I present a methodology designed to determine whether and how global PDF fits might inadvertently 'fit away' signs of new physics in the high-energy tails of the distributions. I showcase a scenario for the High-Luminosity LHC, in which the PDFs may completely absorb such signs of new physics, thus biasing theoretical predictions and interpretations. I discuss strategies to single out the effects in this scenario and disentangle the inconsistencies that stem from them. This study brings to light the synergy between the high luminosity programme at the LHC and present and future low-energy non-LHC measurements of large-sea quark distributions. I also present the potential of fitting simultaneously the PDFs and the new physics signals.