In the context of Self-Interacting Dark Matter as a solution for the small-scale structure problems, we consider the possibility that Dark Matter could have been produced without being in thermal equilibrium with the Standard Model bath. We discuss one by one the following various dark matter production regimes of this kind: freeze-in, reannihilation and dark freeze-out. We exemplify how these mechanisms work in the context of the particularly simple Hidden Vector Dark Matter model. In contrast to scenarios where there is thermal equilibrium with the Standard Model bath, we find two regimes which can easily satisfy all the laboratory and cosmological constraints. These are dark freeze-out with 3-to-2 annihilations and freeze-in via a light mediator. In the first regime, different temperatures in the visible and the Dark Matter sectors allow us to avoid the constraints coming from cosmic structure formation as well as the use of non-perturbative couplings to reproduce the observed relic density. For the second regime, different couplings are responsible for Dark Matter relic density and self-interactions, permitting to surpass BBN, X-ray, CMB and direct detection constraints.

Models with spontaneously broken global lepton number can lead to a pseudoGoldstone boson as a long-lived dark matter candidate. Here we revisit the case of singlet majoron dark matter and discuss multiple constraints. For masses above MeV, this model could lead to a detectable flux of monochromatic mass-eigenstate neutrinos, which have flavor ratios that depend strongly on the neutrino mass hierarchy. We provide a convenient parametrization for the loop-induced majoron couplings to charged fermions that allows us to discuss three-generation effects such as lepton flavor violation. These couplings are independent of the low-energy neutrino parameters but can be constrained by the majoron decays into charged fermions.

We present a detailed study of dark matter phenomenology in low-scale left-right symmetric models. Stability of new fermion or scalar multiplets is ensured by an accidental matter parity that survives the spontaneous symmetry breaking of the gauge group by scalar triplets. The relic abundance of these particles is set by gauge interactions and gives rise to dark matter candidates with masses above the electroweak scale. Dark matter annihilations are thus modified by the Sommerfeld effect, not only in the early Universe, but also today, for instance, in the Center of the Galaxy. Majorana candidates -triplet, quintuplet, bi-doublet, and bi-tripletbring only one new parameter to the model, their mass, and are hence highly testable at colliders and through astrophysical observations. Scalar candidates -doublet and 7-plet, the latter being only stable at the renormalizable level -have additional scalar-scalar interactions that give rise to rich phenomenology. The particles under discussion share many features with the well-known candidates wino, Higgsino, inert doublet scalar, sneutrino, and Minimal Dark Matter. In particular, they all predict a large gamma-ray flux from dark matter annihilations, which can be searched for with Cherenkov telescopes. We furthermore discuss models with unequal left-right gauge couplings, g R = g L , taking the recent experimental hints for a charged gauge boson with 2 TeV mass as a benchmark point. In this case, the dark matter mass is determined by the observed relic density. * Electronic address: Camilo.Alfredo. Garcia.Cely@ulb.ac.be † Electronic address: Julian.Heeck@ulb.ac.be arXiv:1512.03332v2 [hep-ph] 9 Mar 2016 14 4. Collider signatures 15 B. Bi-doublet (2, 2, 0) 15 1. Relic density and indirect detection 17 2. Bi-doublet decays 18 C. Bi-triplet (3, 3, 0) 19 V. Scalar dark matter 21 A. 7-plet (7, 1, 0) ⊕ (1, 7, 0) 21 B. Inert doublet (2, 1, −1) ⊕ (1, 2, −1) 24 VI. Diboson excess 26 A. Diboson excess with g R < g L 26 B. Diboson excess with g R = g L 29 VII. Conclusion 31 Acknowledgements 32 A. Gauge boson masses and decay rates for g L = g R 32 1. Gauge boson masses and mixing 33 2. Gauge boson decay rates 34 B. Real representations of SU (2) 36 C. Mass splitting 37 D. Sommerfeld effect in the center of the galaxy 38E. Relic density in the SU (2) L symmetric limit 41 1. Scalar and fermionic multiplets (2n + 1, 1, 0) ⊕ (1, 2n + 1, 0) 43 2. Chiral bi-multiplets (n, n, 0) 47References 49

Motivated by the Minimal Dark Matter scenario, we consider the annihilation into gamma rays of candidates in the fermionic 5-plet and scalar 7-plet representations of SU (2) L , taking into account both the Sommerfeld effect and the internal bremsstrahlung. Assuming the Einasto profile, we show that present measurements of the Galactic Center by the H.E.S.S. instrument exclude the 5-plet and 7-plet as the dominant form of dark matter for masses between 1 TeV and 20 TeV, in particular, the 5-plet mass leading to the observed dark matter density via thermal freeze-out.We also discuss prospects for the upcoming Cherenkov Telescope Array, which will be able to probe even heavier dark matter masses, including the scenario where the scalar 7-plet is thermally produced. arXiv:1507.05536v2 [hep-ph]

We propose and study a scalar extension of the Standard Model which respects a Z 3 symmetry remnant of the spontaneous breaking of a global U (1) DM symmetry. Consequently, this model has a natural dark matter candidate and a Goldstone boson in the physical spectrum. In addition, the Higgs boson properties are changed with respect to the Standard Model due to the mixing with a new particle. We explore regions in the parameter space taking into account bounds from the measured Higgs properties, dark matter direct detection as well as measurements of the effective number of neutrino species before recombination. The dark matter relic density is determined by three classes of processes: the usual self-annihilation, semi-annihilation and purely dark matter 3 → 2 processes. The latter has been subject of recent interest leading to the so-called 'Strongly Interacting Massive Particle' (SIMP) scenario. We show under which conditions our model can lead to a concrete realization of such scenario and study the possibility that the dark matter self-interactions could address the small scale structure problems. In particular, we find that in order for the SIMP scenario to work, the dark matter mass must be in the range 7 − 115 MeV, with the global symmetry energy breaking scale in the TeV range.