In this work we combine information from relic abundance, direct detection, cosmic microwave background, positron fraction, gamma rays, and colliders to explore the existing constraints on couplings between Dark Matter and Standard Model constituents when no underlying model or correlation is assumed. For definiteness, we include independent vector-like effective interactions for each Standard Model fermion. Our results show that low Dark Matter masses below 20 GeV are disfavoured at the 3Â ÏÂ level with respect to higher masses, due to the tension between the relic abundance requirement and upper constraints on the Dark Matter couplings. Furthermore, large couplings are typically only allowed in combinations which avoid effective couplings to the nuclei used in direct detection experiments.

Sweden

Mattias Blennow

United States

Pilar Coloma

Spain

Enrique Fernández-Martínez

Pedro A.N. Machado

Belgium

Bryan Zaldívar

Global constraints on vector-like WIMP effective interactions

The idea of “Natural SUSY”, understood as a supersymmetric scenario where the fine-tuning is as mild as possible, is a reasonable guide to explore supersymmetric phenomenology. In this paper, we re-examine this issue in the context of the MSSM including several improvements, such as the mixing of the fine-tuning conditions for different soft terms and the presence of potential extra fine-tunings that must be combined with the electroweak one. We give tables and plots that allow to easily evaluate the fine-tuning and the corresponding naturalness bounds for any theoretical model defined at any high-energy (HE) scale. Then, we analyze in detail the complete fine-tuning bounds for the unconstrained MSSM, defined at any HE scale. We show that Natural SUSY does not demand light stops. Actually, an average stop mass below 800 GeV is disfavored, though one of the stops might be very light. Regarding phenomenology, the most stringent upper bound from naturalness is the one on the gluino mass, which typically sets the present level fine-tuning at O 1 % $$ \mathcal{O}\left(1\%\right) $$ . However, this result presents a strong dependence on the HE scale. E.g. if the latter is 10 7 GeV the level of fine-tuning is ∼ four times less severe. Finally, the most robust result of Natural SUSY is by far that Higgsinos should be rather light, certainly below 700 GeV for a fine-tuning of O 1 % $$ \mathcal{O}\left(1\%\right) $$ or milder. Incidentally, this upper bound is not far from ≃ 1 TeV, which is the value required if dark matter is made of Higgsinos.

J. Casas

Jesús Moreno

Sandra Robles

Krzysztof Rolbiecki

What is a natural SUSY scenario?

The aim of this paper is to determine an exact definition of the reheat temperature for a generic perturbative decay of the inflaton. In order to estimate the reheat temperature, there are two important conditions one needs to satisfy: (a) the decay products of the inflaton must dominate the energy density of the universe, i.e. the universe becomes completely radiation dominated, and (b) the decay products of the inflaton have attained local thermodynamical equilibrium. For some choices of parameters, the latter is a more stringent condition, such that the decay products may thermalise much after the beginning of radiation–domination. Consequently, we have obtained that the reheat temperature can be much lower than the standard-lore estimation. In this paper we describe under what conditions our universe could have efficient or inefficient thermalisation, and quantify the reheat temperature for both the scenarios. This result has an immediate impact on many applications which rely on the thermal history of the universe, in particular gravitino abundance.

United Kingdom

Anupam Mazumdar

Quantifying the reheating temperature of the universe

We consider a simple, yet generic scenario in which a new heavy Z ′ gauge boson couples both to SM fermions and to dark matter. In this framework we confront the best LHC limits on an extra gauge boson Z ′ to the constraints on couplings to dark matter from direct detection experiments. In particular we show that the LHC searches for resonant production of dileptons and the recent exclusion limits obtained by the LUX collaboration give complementary constraints. Together, they impose strong bounds on the invisible branching ratio and exclude a large part of the parameter space for generic Z ′ models. Our study encompasses many possible Z ′ models, including SSM, E 6 -inspired or B-L scenario.

Germany

Giorgio Arcadi

France

Yann Mambrini

Michel H.G. Tytgat

Invisible Z ′ and dark matter: LHC vs LUX constraints

We study the genesis of dark matter in the primordial Universe for representative classes of Z′-portals models. For weak-scale Z′ mediators we compute the range of values of the kinetic mixing allowed by WMAP/PLANCK experiments corresponding to a FIMP regime. We show that very small values of δ (10−12≲δ≲10−11) are sufficient to produce the right amount of dark matter. We also analyse the case of very massive gauge mediators, whose mass mZ′ is larger than the reheating temperature, TRH, with a weak-scale coupling gD to ordinary matter. Relic abundance constraints then impose a direct correlation between TRH and the effective scale Λ of the interactions: Λ ∼ 103−105 × TRH. Finally we describe in some detail the process of dark thermalisation and study its consequences on the computation of the relic abundance.

Xiaoyong Chu

Jérémie Quevillon

Thermal and non-thermal production of dark matter via Z′-portal(s)

The popular freeze-out paradigm for Dark Matter (DM) production, relies on DM-baryon couplings of the order of the weak interactions. However, different search strategies for DM have failed to provide a conclusive evidence of such (non-gravitational) interactions, while greatly reducing the parameter space of many representative models. This motivates the study of alternative mechanisms for DM genesis. In the freeze-in framework, the DM is slowly populated from the thermal bath while never reaching equilibrium. In this work, we analyse in detail the possibility of producing a frozen-in DM via a mediator particle which acts as a portal. We give analytical estimates of different freeze-in regimes and support them with full numerical analyses, taking into account the proper distribution functions of bath particles. Finally, we constrain the parameter space of generic models by requiring agreement with DM relic abundance observations.

Enrique Fernandez-Martínez

Freeze-in through portals