Origins of the Isospin Violation of Dark Matter Interactions

TL;DR

This paper investigates the origins of isospin violation in dark matter interactions, analyzing various mediators and models to explain direct detection results while satisfying astrophysical and collider constraints.

Contribution

It systematically explores the origins of isospin violation in dark matter interactions through operator analysis and specific mediator models, proposing a new $U(1)_X$ model with inelastic dark matter.

Findings

Proper isospin violation can reconcile conflicting direct detection results.

A $U(1)_X$ model with inelastic dark matter explains recent experimental signals.

Combining different mediators achieves desired isospin violation and experimental compatibility.

Abstract

Light dark matter (DM) with a large DM-nucleon spin-independent cross section and furthermore proper isospin violation (ISV) $f_n/f_p\approx-0.7$ may provide a way to understand the confusing DM direct detection results. Combing with the stringent astrophysical and collider constraints, we systematically investigate the origin of ISV first via general operator analyses and further via specifying three kinds of (single) mediators: A light $Z'$ from chiral $U(1)_X$, an approximate spectator Higgs doublet (It can explain the $W+jj$ anomaly simultaneously) and color triplets. In addition, although $Z'$ from an exotic $U(1)_X$ mixing with $U(1)_Y$ generating $f_n=0$, we can combine it with the conventional Higgs to achieve proper ISV. As a concrete example, we propose the $U(1)_X$ model where the $U(1)_X$ charged light sneutrino is the inelastic DM, which dominantly annihilates to light dark states such as $Z'$ with sub-GeV mass. This model can address the recent GoGeNT annual modulation consistent with other DM direct detection results and free of exclusions.