Anatomy of Coannihilation with a Scalar Top Partner

TL;DR

This paper examines a dark matter model involving a Majorana fermion and a scalar top partner, analyzing cosmological evolution and experimental detection prospects.

Contribution

It provides a detailed analysis of a simplified coannihilation model with specific focus on parameter space and detection methods, including collider and astrophysical signals.

Findings

Identifies key parameter regions consistent with dark matter relic abundance.

Evaluates the sensitivity of direct, indirect, and collider searches.

Highlights the role of the Yukawa coupling and mass splitting in detection prospects.

Abstract

We investigate a simplified model of dark matter where a Majorana fermion $\chi$ coannihilates with a colored scalar top partner $\tilde{t}$. We explore the cosmological history, with particular emphasis on the most relevant low-energy parameters: the mass splitting between the dark matter and the coannihilator, and the Yukawa coupling $y_\chi$ that connects these fields to the Standard Model top quarks. We also allow a free quartic coupling $\lambda_h$ between a pair of Higgs bosons and $\tilde{t}$ pairs. We pay special attention to the case where the values take on those expected where $\tilde{t}$ corresponds to the superpartner of the right-handed top, and $\chi$ is a bino. Direct detection, indirect detection, and colliders are complementary probes of this simple model.