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On dark matter models with uniquely spin-dependent detection possibilities

Marat Freytsis, Zoltan Ligeti

TL;DR

This work investigates whether direct dark matter detection can be driven by spin-dependent interactions without observable spin-independent signals. It develops an operator-based framework and analyzes renormalizable realizations, demonstrating that loop-induced and velocity/momentum-suppressed SI contributions generally accompany SD signals, except in models with a light pseudoscalar mediator. The authors present a concrete axion-portal model in which a light pseudoscalar yields detectable SD scattering while SI signals stay below reach, and the relic abundance is achieved via appropriate dark sector dynamics. The study highlights the narrow but viable space for SD-dominant detection and emphasizes the need to consider subleading effects and complementary SI/SD channels when evaluating dark matter scenarios.

Abstract

With much higher sensitivities due to coherence effects, it is often assumed that the first evidence for direct dark matter detection will come from experiments probing spin-independent interactions. We explore models that would be invisible in such experiments, but detectable via spin-dependent interactions. The existence of much larger (or even only) spin-dependent tree-level interactions is not sufficient, due to potential spin-independent subdominant or loop-induced interactions. We find that in such a way most models with detectable spin-dependent interactions would also generate detectable spin-independent interactions. Models in which a light pseudoscalar acts as the mediator seem to uniquely evade this conclusion. We present a particular viable dark matter model generating such an interaction.

On dark matter models with uniquely spin-dependent detection possibilities

TL;DR

This work investigates whether direct dark matter detection can be driven by spin-dependent interactions without observable spin-independent signals. It develops an operator-based framework and analyzes renormalizable realizations, demonstrating that loop-induced and velocity/momentum-suppressed SI contributions generally accompany SD signals, except in models with a light pseudoscalar mediator. The authors present a concrete axion-portal model in which a light pseudoscalar yields detectable SD scattering while SI signals stay below reach, and the relic abundance is achieved via appropriate dark sector dynamics. The study highlights the narrow but viable space for SD-dominant detection and emphasizes the need to consider subleading effects and complementary SI/SD channels when evaluating dark matter scenarios.

Abstract

With much higher sensitivities due to coherence effects, it is often assumed that the first evidence for direct dark matter detection will come from experiments probing spin-independent interactions. We explore models that would be invisible in such experiments, but detectable via spin-dependent interactions. The existence of much larger (or even only) spin-dependent tree-level interactions is not sufficient, due to potential spin-independent subdominant or loop-induced interactions. We find that in such a way most models with detectable spin-dependent interactions would also generate detectable spin-independent interactions. Models in which a light pseudoscalar acts as the mediator seem to uniquely evade this conclusion. We present a particular viable dark matter model generating such an interaction.

Paper Structure

This paper contains 10 sections, 48 equations, 3 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Prospects of Direct Detection
  3. General Considerations
  4. Operator Analysis
  5. Renormalizable Models
  6. Loops and Subleading Interactions
  7. The Axion Portal
  8. Conclusions
  9. Nuclear Matrix Elements
  10. Cross Sections

Figures (3)

  • Figure 1: The tree and loop level contributions to scattering of Majorana fermions through a $Z$ boson. For all box diagrams, the crossed box diagram is included in calculations but not depicted. In the last diagram, a Higgs mediates the scattering through a $Z$ loop.
  • Figure 2: The tree and loop level contributions to scattering of Majorana fermions through a $s$-channel scalar.
  • Figure 3: The tree and loop level contributions to scattering DM mediated by a light pseudoscalar. The dotted line can represent either a scalar, fermion, or vector boson.