Tasting Flavoured Majorana Dark Matter

TL;DR

This paper explores a flavoured Majorana dark matter model within the Dark Minimal Flavour Violation framework, analyzing its parameter space against experimental constraints and proposing distinctive collider signatures.

Contribution

It introduces a new flavoured Majorana dark matter model, analyzing its compatibility with experimental data and its potential to explain CP asymmetry in charm decays.

Findings

Majorana dark matter can explain CP asymmetry measurements.

The model predicts distinctive same-sign top quark signatures at the LHC.

Parameter space is constrained by collider, cosmology, and flavor physics data.

Abstract

We study a simplified model of flavoured Majorana dark matter in the Dark Minimal Flavour Violation framework. The model extends the Standard Model by a dark matter flavour triplet and a scalar mediator, through which the new dark fermions couple to right-handed up-type quarks. This interaction is governed by a new coupling matrix $\lambda$ which is assumed to constitute the only new source of flavour and CP violation. We analyse the parameter space of this model by using constraints from collider searches, $D^0-\bar{D}^0$ mixing, cosmology and direct dark matter searches. Throughout our study, we point out crucial differences between the Majorana and Dirac dark matter cases. After performing a combined analysis within the context of all the experimental constraints mentioned above, we analyse which flavour for the dark matter particle is preferred by experimental data. We further investigate if this model is capable of explaining the large measured value of the direct CP asymmetry $\Delta A^\text{dir}_{CP}$ in charm decays. We find that significant enhancements with respect to the Standard Model expectation are compatible with all constraints, and even the central value of the measurement can be reached. We also advertise the flavour-violating final state with two same-sign top quarks produced in association with missing transverse energy as a smoking-gun signature for flavoured Majorana dark matter at the LHC.