# Loop-induced direct detection signatures from CP-violating scalar mediators

## TL;DR

This paper explores how loop-induced effects from CP-violating scalar mediators can produce detectable dark matter signals in direct detection experiments, especially when tree-level interactions are suppressed.

## Contribution

It introduces a new method to decompose two-loop contributions into simpler one-loop diagrams, enhancing the calculation of dark matter-gluon interactions.

## Key findings

- Loop effects can dominate direct detection signals in certain CP-violating scenarios.
- The combined recoil spectrum from tree and loop interactions can reveal unique signatures.
- A novel decomposition method simplifies complex two-loop calculations.

## Abstract

We investigate direct detection signatures of dark matter particles interacting with quarks via a light spin-0 mediator with general CP phases. Since tree-level scattering may be strongly suppressed in the non-relativistic limit, loop contributions play an important role and can lead to observable signals in near-future experiments. We study the phenomenology of different mediator masses and CP phases with an emphasis on scenarios with maximal CP violation and Higgs portal models. Intriguingly, the sum of the rates obtained at tree- and loop-level can give a characteristic recoil spectrum not obtainable from a single type of interaction. We furthermore develop a novel method for decomposing the two-loop contribution to effective interactions between dark matter and gluons into two separate one-loop diagrams, which in our case substantially simplifies the calculation of the important top-quark contribution.