Light stops, blind spots, and isospin violation in the MSSM

TL;DR

This paper investigates how specific MSSM parameter regions, especially blind spots, affect dark matter detection, revealing significant isospin violation and emphasizing the importance of hadronic uncertainties in future experiments.

Contribution

It derives analytic expressions for WIMP-nucleon scattering in simplified MSSM models and explores the impact of blind spots and isospin violation on detection prospects.

Findings

Identification of parameter regions with suppressed cross sections.

Large isospin violation near blind spots.

Highlighting the role of hadronic uncertainties in detection sensitivity.

Abstract

In the framework of the MSSM, we examine several simplified models where only a few superpartners are light. This allows us to study WIMP--nucleus scattering in terms of a handful of MSSM parameters and thereby scrutinize their impact on dark matter direct-detection experiments. Focusing on spin-independent WIMP--nucleon scattering, we derive simplified, analytic expressions for the Wilson coefficients associated with Higgs and squark exchange. We utilize these results to study the complementarity of constraints due to direct-detection, flavor, and collider experiments. We also identify parameter configurations that produce (almost) vanishing cross sections. In the proximity of these so-called blind spots, we find that the amount of isospin violation may be much larger than typically expected in the MSSM. This feature is a generic property of parameter regions where cross sections are suppressed, and highlights the importance of a careful analysis of the nucleon matrix elements and the associated hadronic uncertainties. This becomes especially relevant once the increased sensitivity of future direct-detection experiments corners the MSSM into these regions of parameter space.