Singlet Scalar Dark Matter: monochromatic gamma rays and metastable vacua

TL;DR

This paper investigates real scalar singlet dark matter, calculating gamma-ray signals from annihilation, deriving constraints from gamma-ray line observations, and analyzing vacuum stability, revealing new parameter space exclusions and implications for dark matter detection.

Contribution

It provides the first detailed calculation of gamma-ray line signals from scalar singlet dark matter and compares these with experimental constraints, also analyzing vacuum metastability.

Findings

Gamma-ray line limits exclude new parameter regions.

Some excluded regions overlap with potential dark matter explanations for CDMS signals.

Vacuum metastability analysis shows gamma-ray limits are relevant for long-lived metastable vacua.

Abstract

We calculate the pair-annihilation cross section of real scalar singlet dark matter into two mono-energetic photons. We derive constraints on the theory parameter space from the Fermi limits on gamma-ray lines, and we compare with current limits from direct dark matter detection. We show that the new limits, albeit typically relevant only when the dark matter mass is close to half the Standard Model Higgs mass, rule out regions of the theory parameter space that are otherwise not constrained by other observations or experiments. In particular, the new excluded regions partly overlap with the parameter space where real scalar singlet dark matter might explain the anomalous signals observed by CDMS. We also calculate the lifetime of unstable vacuum configurations in the scalar potential, and show that the gamma-ray limits are quite relevant in regions where the electro-weak vacuum is meta-stable with a lifetime longer than the age of the universe.