Prospects for sub-EW-scale ALP searches via $\gamma+b\bar{b}$ signatures at the LHC using jet substructure techniques

TL;DR

This paper investigates the potential of the LHC to detect light axion-like particles decaying into b-quark pairs with an associated photon, using jet substructure techniques to extend sensitivity below the electroweak scale.

Contribution

It proposes a novel search strategy for sub-EW-scale ALPs at the LHC via $ ext{γ}+bar{b}$ signatures, utilizing jet substructure to improve detection prospects.

Findings

Projected exclusions on ALP-fermion couplings in unexplored parameter space.

Demonstrated the effectiveness of jet substructure techniques for light resonance searches.

Highlighted the importance of lower trigger thresholds for enhanced sensitivity.

Abstract

The current Large Hadron Collider (LHC) data show no clear indication of new physics and only incremental improvements are anticipated at the energy frontier in the near future. However, while the focus of the LHC has been on constraining TeV scale physics, new particles could still be hiding below the electroweak scale. In order to obtain sensitivity to a new light boson with couplings to SM fermions, a potentially promising decay channel, for resonances with mass $\gtrsim {\cal O}(10)$ GeV, would be the decay to $b\bar b$ pairs. The measurement of such signatures is challenging due to the trigger requirements at the LHC. In this work, we explore the LHC sensitivity to a light pseudoscalar, or axion-like particle (ALP), in the $b\bar{b}$ final state with an associated photon, using jet substructure techniques, in the mass range between 10 GeV and 100 GeV. We obtain projected exclusions on the ALP-fermion coupling in a region of phase space which has not so far been probed by direct searches. We further discuss the impact that lower trigger thresholds may have on the LHC reach.