Heavy long-lived coannihilation partner from inelastic Dark Matter model and its signatures at the LHC

TL;DR

This paper explores a model of inelastic dark matter with a long-lived coannihilation partner, leading to displaced collider signatures and expanding the viable mass range for dark matter detection at the LHC.

Contribution

It introduces a new inelastic scalar dark matter model with a broken symmetry, emphasizing long-lived coannihilation partners and their collider signatures.

Findings

High-luminosity LHC can detect coannihilation partners around 100--700 GeV.

Long-lived partners produce displaced decay signatures at colliders.

The model satisfies relic abundance and detection constraints.

Abstract

The coannihilation mechanism is a well-motivated alternative to the simple thermal freeze-out mechanism, where the dark matter relic density can be obtained through the coannihilation with a partner particle of similar mass with dark matter. When the partner particle is neutral, the inelastic nature of dark matter can help it to escape the direct detection limits. In this work, we focus on the coannihilation scenario in which the annihilation cross section is dominated by the partner-partner pair annihilation. We pay special interest on the parameter space where the coannihilation partner is long-lived, which leads to displaced signatures at the collider. In such case, it opens the heavy mass parameter space for the coannihilation dark matter, comparing with those dominated by the partner-dark matter annihilation. Specifically, we propose an inelastic scalar dark matter model with a broken symmetry, which realizes the domination of partner-partner pair annihilation. Then, we study two different realizations of the coannihilation partner decay and the existing constraints from the relic abundance, direct and indirect dark matter detection and the collider searches. We focus on the channel that the long-lived coannihilation partner decays to dark matter plus leptons. The high-luminosity LHC can reach good sensitivities for such heavy dark matter and coannihilation partner around 100--700 GeV.