Exploring the Hadronic Axion Window via Delayed Neutralino Decay to Axinos at the LHC

TL;DR

This paper investigates the potential to detect axinos, the superpartners of axions, at the LHC through displaced neutralino decays, focusing on the hadronic axion window within the SUSY framework.

Contribution

It introduces a novel collider signature for axinos via displaced neutralino decays, highlighting the detectability within the hadronic axion window at 14 TeV LHC.

Findings

Neutralino decay lengths fit within ATLAS detector range.

Displaced decay signatures can mimic other long-lived neutralino scenarios.

Cosmological viability of the scenario is briefly discussed.

Abstract

The addition of the QCD axion to the Minimal Supersymmetric Standard Model (MSSM) not only solves the strong CP problem but also modifies the dark sector with new dark matter candidates. While SUSY axion phenomenology is usually restricted to searches for the axion itself or searches for the ordinary SUSY particles, this work focuses on scenarios where the axion's superpartner, the axino, may be detectable at the Large Hadron Collider (LHC) in the decays of neutralinos displaced from the primary vertex. In particular, we focus on the KSVZ axino within the hadronic axion window. The decay length of neutralinos in this scenario easily fits the ATLAS detector for SUSY spectra expected to be testable at the 14 TeV LHC. We compare this signature of displaced decays to axinos to other well motivated scenarios containing a long lived neutralino which decays inside the detector. These alternative scenarios can in some cases very closely mimic the expected axino signature, and the degree to which they are distinguishable is discussed. We also briefly comment on the cosmological viability of such a scenario.