Anapole Moment of Majorana Fermions and Implications for Direct Detection of Neutralino Dark Matter

TL;DR

This paper calculates the one-loop induced anapole moment of Majorana fermions, especially the neutralino, and discusses its significance for direct dark matter detection.

Contribution

It provides a gauge-invariant calculation of the neutralino's anapole moment within the MSSM, highlighting its role in dark matter detection strategies.

Findings

Anapole moment is the only electromagnetic multipole for Majorana fermions.

Calculated the anapole moment for neutralino in various MSSM limits.

Discussed the impact of the anapole moment on direct dark matter detection.

Abstract

For Majorana fermions the anapole moment is the only allowed electromagnetic multipole moment. In this work we calculate the anapole moment induced at one-loop by the Yukawa and gauge interactions of a Majorana fermion, using the pinch technique to ensure the finiteness and gauge-invariance of the result. As archetypical example of a Majorana fermion, we calculate the anapole moment for the lightest neutralino in the Minimal Supersymmetric Standard Model, and specifically in the bino, wino and higgsino limits. Finally, we briefly discuss the implications of the anapole moment for the direct detection of dark matter in the form of Majorana fermions.