The idea of dark matter particles coupled only gravitationally is minimalist yet viable. Assuming an additional $Z_2$-breaking linear coupling of scalar curvature to the dark matter scalar (gravity portal) Refs. arXiv:1603.03696 and arXiv:1611.00725 claimed a strong parametric growth of the dark matter particle decay rate with its mass, which implies pronounced phenomenological signatures for the model. This peculiarity was attributed by the authors to the enhancement due to the presence of longitudinal gauge bosons in the final state. Quite unfortunately there were overlooked cancellations in the tree-level amplitudes. There is no miracle: all perturbative decay rates are suppressed by the strong coupling scale.
Fermionic dark matter interacting with the Standard Model sector through a pseudoscalar portal could evade the direct detection constraints while preserving a WIMP miracle. We study the LHC constraints on the pseudoscalar production in simplified models with the pseudoscalar either dominantly coupled to b quarks or tau leptons and explore their implications for the GeV excesses in gamma ray observations. We also investigate models with new vector-like fermions that could realize the simplified models of pseudoscalar portal dark matter. These models yield new decay channels and signatures of ve…
We examine a real electroweak triplet scalar field as dark matter, abandoning the requirement that its relic abundance is determined through freeze out in a standard cosmological history (a situation which we refer to as a 'miracle-less WIMP'). We extract the bounds on such a particle from collider searches, searches for direct scattering with terrestrial targets, and searches for the indirect products of annihilation. Each type of search provides complementary information, and each is most effective in a different region of parameter space. LHC searches tend to be highly dependent on the mass…
We examine the possibility that dark matter (DM) consists of a gapped continuum, rather than ordinary particles. A Weakly-Interacting Continuum (WIC) model, coupled to the Standard Model via a Z-portal, provides an explicit realization of this idea. The thermal DM relic density in this model is naturally consistent with observations, providing a continuum counterpart of the "WIMP miracle". Direct detection cross sections are strongly suppressed compared to ordinary Z-portal WIMP, thanks to a unique effect of the continuum kinematics. Continuum DM states decay throughout the history of the univ…
In the classic type I seesaw mechanism with very heavy right-handed (RH) neutrinos, it is possible to account for dark matter via RH neutrino portal couplings to a feebly interacting massive particle (FIMP) dark sector. However, for large RH neutrino masses, gravity can play an important role. We study the interplay between the neutrino portal through the right-handed neutrinos and the gravity portal through the massless spin-2 graviton in producing dark matter particles in the early universe. As a concrete example, we consider the minimal and realistic Littlest Seesaw model with two RH neutri…
In the so-called Planckian Interacting Dark Matter (PIDM) scenario, superheavy dark matter particles are produced after inflation by gravity-mediated interactions through the freeze-in mechanism. In the minimal PIDM model, the absence of any additional direct coupling with Standard Model particles is assumed. However, for scalar dark matter particles there is no symmetry that suppresses the Higgs portal coupling. In this paper, we therefore study the impact of a non-zero interaction with the Higgs field on the PIDM paradigm for scalar dark matter. In particular, we fully explore the model para…
There are indications that an asymptotically safe UV completion of the Standard Model with gravity could constrain the Higgs self-coupling, resulting in a prediction of the Higgs mass close to the vacuum stability bound in the Standard Model. The predicted value depends on the top quark mass and comes out somewhat higher than the experimental value if the current central value for the top quark mass is assumed. Beyond the Standard Model, the predicted value also depends on dark fields coupled through a Higgs portal. Here we study the Higgs self-coupling in a toy model of the Standard Model wit…
We propose a new scenario where dark matter belongs to a secluded sector coupled to the Standard Model through energy--momentum tensors. Our model is motivated by constructions where gravity {\it emerges} from a hidden sector, the graviton being identified by the kinetic term of the fields in the secluded sector. Supposing that the lighter particle of the secluded sector is the dark component of the Universe, we show that we can produce it in a sufficiently large amount despite the suppressed couplings of the theory, thanks to large temperatures of the thermal bath in the early stage of the Un…
Global symmetry can guarantee the stability of dark matter particles (DMps). However, the nonminimal coupling between dark matter (DM) and gravity can destroy the global symmetry of DMps, which in turn leads to their decay. Under the framework of nonminimal coupling between scalar singlet dark matter (ssDM) and gravity, it is worth exploring to what extent the symmetry of ssDM is broken. It is suggested that the total amount of decay products of ssDM cannot exceed current observational constraints. Along these lines, the data obtained with satellites such as Fermi-LAT and AMS-02 can limit the …
Dark matter (DM) constitutes 85% of the matter in the Universe. However, its specific particle property is still unclear. The fundamentals of DM particles subject to gravitational interaction, and that the lepton excess in cosmic rays may originate from DM particles, inspired us to investigate DM particle properties beyond the standard model. We assume that a leptophilic SU(2) doublet exists in nature as the mediator connecting DM with visible leptons. Since general relativity is not renormalizable at the quantum level, it should be regarded as an effective field theory's leading order term. O…
We show that a minimal scenario, utilizing only the graviton as an intermediate messenger between the inflaton, the dark sector and the Standard Model (SM), is able to generate $simultaneously$ the observed relic density of dark matter (DM), the baryon asymmetry through leptogenesis, as well as a sufficiently hot thermal bath after inflation. We assume an inflaton potential of the form $V(ϕ)\propto ϕ^k$ about the minimum at the end of inflation. The possibility of reheating via minimal gravitational interactions has been excluded by constraints on dark radiation for excessive gravitational wav…
We discuss possibilities of generating a Majorana mass for the neutron from topological quantum gravity effects which survive at mesoscopic scales from decoherence. We show how virtual micro-black hole (BH) pairs with skyrme/baryon hairs induce a neutron-antineutron transition which can be tested in next generation of experiments. Such effects do not destabilize the proton. We also discuss how BHs with mix ordinary and mirror baryon hairs can mediate neutron-mirror neutron mixings.
It is well-known since the works of Utiyama and Kibble that the gravitational force can be obtained by gauging the Poincaré group, which puts gravity on the same footing as the Standard Model fields. The resulting theory -- Einstein-Cartan gravity -- inevitably contains four-fermion and scalar-fermion interactions that originate from torsion associated with spin degrees of freedom. We show that these interactions lead to a novel mechanism for producing singlet fermions in the Early Universe. These fermions can play the role of dark matter particles. The mechanism is operative in a large range …
Einstein-Cartan gravity which is an alternative formulation of general relativity introduces new degrees of freedom contained in the torsion field which encodes the torsion feature of spacetime. Interestingly, the torsion field couples to all fermions through its axial-vector mode with a universal coupling $η=1/8$ which is possible to change under the quantum effects. We argue that Einstein-Cartan gravity provides a significant portal to probe $A'$ dark gauge boson which resides in dark sector existing as an invisible world parallel to our own and couples to the standard model (SM) particles t…
We consider the effects of non-minimal couplings to curvature of the form $ξ_S S^2 R$, for three types of scalars: the Higgs boson, the inflaton, and a scalar dark matter candidate. We compute the abundance of dark matter produced by these non-minimal couplings to gravity and compare to similar results with minimal couplings. We also compute the contribution to the radiation bath during reheating. The main effect is a potential augmentation of the maximum temperature during reheating. A model independent limit of $\mathcal{O}(10^{12})$ GeV is obtained. For couplings $ξ_S \gtrsim \mathcal{O}(1)…
School of Physics and Astronomy, University of Southampton（南安普顿大学物理与天文学院）；Department of Physics, Lund University（隆德大学物理系）；Departamento de Física da Universidade de Aveiro（阿威罗大学物理系）；Centre for Research and Development in Mathematics and Applications (CIDMA)（数学与应用研发中心（CIDMA））；Laboratório de Instrumentação e Física Experimental de Partículas (LIP), Universidade do Minho（米尼奥大学粒子实验与仪器实验室（LIP））；Departamento de Física, Escola de Ciências, Universidade do Minho（米尼奥大学理学院物理系）；Khon Kaen Particle Physics and Cosmology Theory Group (KKPaCT), Department of Physics, Faculty of Science, Khon Kaen University（孔敬大学理学院物理系孔敬粒子物理与宇宙学理论组（KKPaCT））
William I. Fine Theoretical Physics Institute, School of Physics and Astronomy, University of Minnesota（明尼苏达大学物理与天文学院威廉·I·芬理论物理研究所）；Université Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎萨克雷大学）；University of Minnesota（明尼苏达大学）
Search for the production of dark gauge bosons in the framework of Einstein-Cartan portal in the simulation of proton-proton collisions at $\sqrt{s} = 13.6$ TeV
We consider the production of matter and radiation during reheating after inflation, restricting our attention solely to gravitational interactions. Processes considered are the exchange of a graviton, $h_{μν}$, involved in the scattering of the inflaton or particles in the newly created radiation bath. In particular, we consider the gravitational production of dark matter (scalar or fermionic) from the thermal bath as well as from scattering of the inflaton condensate. We also consider the gravitational production of radiation from inflaton scattering. In the latter case, we also derive a low…
Since the current evidence of its existence is revealed only through its gravitational influence, the way dark matter couples to gravity must be then of primary importance. Here, unlike the standard model sector which is typically coupled to metric, dark matter is supposed to couple only to spacetime affine connection through a $Z_2$-symmetry breaking term. We show that this structure leads to a coupling between dark matter, which is considered scalar, and the standard model Higgs potential. This induces dark matter decays into standard model particles through the Higgs which acts as a portal …
We study the possibility of realising cosmic inflation, dark matter (DM), baryon asymmetry of the universe (BAU) and light neutrino masses in non-supersymmetric minimal gauged $B-L$ extension of the standard model with three right handed neutrinos. The singlet scalar field responsible for spontaneous breaking of $B-L$ gauge symmetry also plays the role of inflaton by virtue of its non-minimal coupling to gravity. While the lightest right handed neutrino is the DM candidate, being stabilised by an additional $Z_2$ symmetry, we show by performing a detailed renormalisation group evolution (RGE) …
We generalize dark matter production to a two-metric framework whereby the physical metric, which couples to the Standard Model (SM), is conformally and/or disformally related to the metric governing the gravitational dynamics. We show that this setup is naturally present in many Ultra Violet (UV) constructions, from Kähler moduli fields to tensor-portal models, and from emergent gravity to supergravity models. In this setting we study dark matter production in the early Universe resulting from both scatterings off the thermal bath and the radiative decay of the inflaton. We also take into acc…
