Abstract
We consider a twin WIMP scenario whose twin sector contains a full dark copy of the SM hadrons, where the lightest twin particles are twin pions. By analogy to the standard WIMP paradigm, the dark matter (DM) freezes out through twin electroweak interactions, and annihilates into a dark shower of light twin hadrons. These are either stable or decay predominantly to standard model (SM) photons. We show that this ‘hadrosymmetric’ scenario can be consistent with all applicable astrophysical, cosmological and collider constraints. In order to decay the twin hadrons before the big-bang nucleosynthesis epoch, an additional portal between the SM and twin sector is required. In most cases we find this additional mediator is within reach of either the LHC or future intensity frontier experiments. Furthermore, we conduct simulations of the dark shower and consequent photon spectra. We find that fits of these spectra to the claimed galactic center gamma-ray excess seen by Fermi -LAT non-trivially coincide with regions of parameter space that both successfully generate the observed DM abundance and exhibit minimal fine-tuning.
Highlights
The twin Higgs (TH) mechanism provides a natural means to stabilize the electroweak scale up to O(10 TeV) with uncolored top partners, that belong to a twin dark copy of the standard model (SM) [1, 2]
We find that for a Dirac twin WIMP (T-WIMP), there is a viable region of parameter space in which these dark showers may reproduce the putative galactic center γ-ray excess (GCE), claimed to be seen in Fermi -LAT data from the central regions of the Milky Way galaxy [31,32,33,34,35,36,37,38,39] and dwarf spheroidal galaxies [40, 41], as well as simultaneously generate an appropriate amount of dark matter (DM) and exhibit minimal fine-tuning. (See Refs. [39, 42,43,44,45,46,47,48] which discuss alternative astrophysical explanations for the GCE, or dispute observations of an excess in dwarf spheroidal galaxies [49].) Alternatively, treating observed photon fluxes as a conservative upper bound, there are large regions of parameter space are not excluded by current galactic center γ-ray data
We have studied a twin WIMP (T-WIMP) scenario whose twin sector contains a mirror copy of the SM hadrons – i.e. all three twin quark generations with three light quark flavors – but no dark radiation – i.e. no light twin leptons or photons
Summary
The twin Higgs (TH) mechanism provides a natural means to stabilize the electroweak scale up to O(10 TeV) with uncolored top partners, that belong to a twin dark copy of the standard model (SM) [1, 2]. Naturalness does not significantly constrain the remaining features of the twin sector, but all TH models contain a lightest twin particle (LTP) and a lightest twin hadron (LTH) The latter is either a bound state of twin quarks or a twin glueball. In this work we focus on TH models featuring T-WIMP candidates They require no additional light states with SM charges, twin Higgs models may produce striking signatures in a variety of direct and indirect searches. The decays of the LTH may generate (possibly displaced) collider signatures, while a twin neutrino LTP contributes ∆Neff 0.075 [6, 7], that is potentially detectable in the future These models can further admit a twin tau T-WIMP that annihilates into twin hadrons, some of which in turn decay to bb or τ τpairs V, along with both fits to GCE spectra and constraints from γ-ray fluxes
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