Looking for new strategies to probe low mass axion-like particles in ultraperipheral heavy-ion collisions at the LHC

TL;DR

This paper explores novel detection strategies for low mass axion-like particles decaying into photons in ultraperipheral heavy-ion collisions at the LHC, utilizing vertex reconstruction and photon conversion techniques.

Contribution

It proposes a new search method for low mass ALPs in heavy-ion collisions, focusing on vertex displacement and photon conversion to improve detection sensitivity.

Findings

Predicted ALP and photon distributions in rapidity and transverse momentum.

Estimated fiducial cross-sections for different ALP masses and couplings.

Demonstrated the feasibility of using decay vertex displacement for ALP identification.

Abstract

The possibility of searching for long-lived axion-like particles (ALPs) decaying into photons is investigated in ultraperipheral $PbPb$ collisions at the Large Hadron Collider (LHC). We propose a search strategy for low mass ALPs using the LHCb and ALICE experiments. The ALP identification is performed by requiring the decay vertex be reconstructed outside the region where a primary vertex is expected, which strongly suppress the contribution associated with the decay of light mesons. We also use the fact that a fraction of the photons convert into electron-positron pairs, allowing the reconstruction of the particle decay position. We present the predictions for the pseudo - rapidity and transverse momentum distributions of the ALPs and photons. Moreover, predictions for the fiducial cross-sections, derived considering the characteristics of the ALICE and LHCb detectors, are presented for different values of the ALP mass and the ALP - photon coupling.