Minimal Dark Matter

TL;DR

Minimal Dark Matter identifies a small set of ${ m SU}(2)_L$ multiplets with automatic stability, determined solely by gauge interactions and the representation chosen. Coannihilations fix the thermal relic mass scale to several TeV, with the fermionic ${ m SU}(2)_L$ quintuplet ($Y=0$) at $M\approx 4.4$ TeV being the primary viable candidate; a charged partner with $oxed{\Delta M \approx 166\text{ MeV}}$ remains slightly heavier, producing distinctive collider tracks. Direct detection is loop-suppressed for $Y=0$ and near-future experiments approach the predicted $\sigma_{\rm SI} \sim 10^{-44}$ cm$^2$, while $Y\neq 0$ is excluded at tree level unless non-minimal mechanisms suppress $Z$-couplings. At colliders, long-lived charged states yield clean displaced-vertex signatures; indirect detection could probe resonant annihilations near special mass values, making the model testable across multiple experimental fronts. The work provides a highly predictive, gauge-based DM scenario with clear, falsifiable signatures.

Abstract

A few multiplets that can be added to the SM contain a lightest neutral component which is automatically stable and provides allowed DM candidates with a non-standard phenomenology. Thanks to coannihilations, a successful thermal abundance is obtained for well defined DM masses. The best candidate seems to be a SU(2)_L fermion quintuplet with mass 4.4 TeV, accompanied by a charged partner 166 MeV heavier with life-time 1.8 cm, that manifests at colliders as charged tracks disappearing in pi^\pm with 97.7% branching ratio. The cross section for usual NC direct DM detection is sigma_SI = f^2 1.0 10^-43 cm^2 where f ~ 1 is a nucleon matrix element. We study prospects for CC direct detection and for indirect detection.

Figures (2)

• Figure 1: One loop DM/quark scattering for fermionic MDM with $Y=0$. Two extra graphs involving the four particle vertex exist in the case of scalar MDM.
• Figure 2: Spin-independent cross sections per nucleon of MDM candidates assuming the matrix element $f=1/3$. Fermionic MDM candidates are denoted as blue circles; scalars as red diamonds. The fully successful candidates (automatically stable $Y=0$ multiplets with $n=5,7$) are represented by filled symbols. We also show, as large empty symbols, the $Y=0$ candidates that require a stabilization mechanism and, with smaller symbols, those with $Y\neq 0$ (viable if an additional mechanism forbids a much larger cross section mediated by a $Z$ boson). The dashed lines indicate the sensitivity of some future experiments future. The cloud indicates the range of values favoured by a minimal SUSY model.