Inflation and dark matter after spontaneous Planck scale generation by hidden chiral symmetry breaking

Dynamical chiral symmetry breaking in a QCD-like hidden sector is used to generate the Planck mass and the electroweak scale including the heavy right-handed neutrino mass. A real scalar field transmits the energy scale of the hidden sector to the visible sectors, playing besides a role of inflaton in the early Universe while realizing a Higgs-inflation-like model. Our dark matter candidates are hidden pions that raise due to dynamical chiral symmetry breaking. They are produced from the decay of inflaton. Unfortunately, it will be impossible to directly detect them, because they are super heavy (109 ∼ 12 GeV), and moreover the interaction with the visible sector is extremely suppressed.

Dark matter to baryon ratio from scalar triplets decay in type-II seesaw

We propose a minimal model for the cosmic coincidence problem $$\Omega _\mathrm{DM}/\Omega _B \sim 5$$ Ω DM / Ω B ∼ 5 and neutrino mass in a type-II seesaw scenario. We extend the standard model of particle physics with a $$\mathrm SU(2)$$ S U ( 2 ) singlet leptonic Dirac fermion $$\chi $$ χ , which represents the candidate of dark matter (DM), and two triplet scalars $$\Delta _{1,2}$$ Δ 1 , 2 with hierarchical masses. In the early Universe, the CP violating out-of-equilibrium decay of lightest $$\Delta $$ Δ generates a net $$B-L$$ B - L asymmetry in the visible sector (comprising of SM fields), where B and L represents the total baryon and lepton number respectively. A part of this asymmetry gets transferred to the dark sector (comprising of DM $$\chi $$ χ ) through a dimension eight operator which conserves $$B-L$$ B - L . Above the electroweak phase transition, the $$B-L$$ B - L asymmetry of the visible sector gets converted to a net B-asymmetry by the $$B+L$$ B + L violating sphalerons, while the $$B-L$$ B - L asymmetry of the dark sector remains untouched which we see today as relics of DM. We show that the observed DM abundance can be explained for a DM mass about 8 GeV. We then introduce an additional singlet scalar field $$\phi $$ ϕ which mixes with the SM-Higgs to annihilate the symmetric component of the DM resonantly which requires the singlet scalar mass to be twice the DM mass, i.e. around 16 GeV, which can be searched at collider experiments. In our model, the active neutrinos also get small masses by the induced vacuum expectation value (vev) of the triplet scalars $$\Delta _{1,2}$$ Δ 1 , 2 . In the later part of the paper we discuss all the constraints on model parameters coming from invisible Higgs decay, Higgs signal strength, DM direct detection and relic density of DM.

A cosmologically consistent millicharged dark matter solution to the EDGES anomaly of possible string theory origin

Analysis of EDGES data shows an absorption signal of the redshifted 21-cm line of atomic hydrogen at z ∼ 17 which is stronger than expected from the standard ΛCDM model. The absorption signal interpreted as brightness temperature T21 of the 21-cm line gives an amplitude of $$ -{500}_{-500}^{+200} $$ − 500 − 500 + 200 mK at 99% C.L. which is a 3.8σ deviation from what the standard ΛCDM cosmology gives. We present a particle physics model for the baryon cooling where a fraction of the dark matter resides in the hidden sector with a U(1) gauge symmetry and a Stueckelberg mechanism operates mixing the visible and the hidden sectors with the hidden sector consisting of dark Dirac fermions and dark photons. The Stueckelberg mass mixing mechanism automatically generates a millicharge for the hidden sector dark fermions providing a theoretical basis for using millicharged dark matter to produce the desired cooling of baryons seen by EDGES by scattering from millicharged dark matter. We compute the relic density of the millicharged dark matter by solving a set of coupled equations for the dark fermion and dark photon yields and for the temperature ratio of the hidden sector and the visible sector heat baths. For the analysis of baryon cooling, we analyze the evolution equations for the temperatures of baryons and millicharged dark matter as a function of the redshift. We exhibit regions of the parameter space which allow consistency with the EDGES data. We note that the Stueckelberg mechanism arises naturally in strings and the existence of a millicharge would point to its string origin.

Asymmetric accidental composite dark matter

The goal of this work is to find the simplest UV completion of Accidental Composite Dark Matter Models (ACDM) that can dynamically generate an asymmetry for the DM candidate, the lightest dark baryon (DCb), and simultaneously annihilate the symmetric component. In this framework the DCb is a bound state of a confining SU(N)DC gauge group, and can interact weakly with the visible sector. The constituents of the DCb can possess non-trivial charges under the Standard Model gauge group. The generation of asymmetry for such candidate is a two-flavor variation of the out-of-equilibrium decay of a heavy scalar, with mass Mϕ ≳ 1010 GeV. Below the scale of the scalars, the models recover accidental stability, or long-livedness, of the DM candidate. The symmetric component is annihilated by residual confined interactions provided that the mass of the DCb mDCb ≲ 75 TeV. We implement the mechanism of asymmetry generation, or a variation of it, in all the original ACDM models, managing to generate the correct asymmetry for DCb of masses in this range. For some of the models found, the stability of the DM candidate is not spoiled even considering generic GUT completions or asymmetry generation mechanisms in the visible sector.

Inflation and supersymmetry breaking in Higgs-R2 supergravity

We propose a new construction of the supergravity inflation as an UV completion of the Higgs-R2 inflation. In the dual description of R2-supergravity, we show that there appear dual chiral superfields containing the scalaron or sigma field in the Starobinsky inflation, which unitarizes the supersymmetric Higgs inflation with a large non-minimal coupling up to the Planck scale. We find that a successful slow-roll inflation is achievable in the Higgs-sigma field space, but under the condition that higher curvature terms are introduced to cure the tachyonic mass problems for spectator singlet scalar fields. We also discuss supersymmetry breaking and its transmission to the visible sector as a result of the couplings of the dual chiral superfields and the non-minimal gravity coupling of the Higgs fields.

Hidden dark matter from Starobinsky inflation

The Starobinsky inflation model is one of the simplest inflation models that is consistent with the cosmic microwave background observations. In order to explain dark matter of the universe, we consider a minimal extension of the Starobinsky inflation model with introducing the dark sector which communicates with the visible sector only via the gravitational interaction. In Starobinsky inflation model, a sizable amount of dark-sector particle may be produced by the inflaton decay. Thus, a scalar, a fermion or a vector boson in the dark sector may become dark matter. We pay particular attention to the case with dark non-Abelian gauge interaction to make a dark glueball a dark matter candidate. In the minimal setup, we show that it is difficult to explain the observed dark matter abundance without conflicting observational constraints on the coldness and the self-interaction of dark matter. We propose scenarios in which the dark glueball, as well as other dark-sector particles, from the inflaton decay become viable dark matter candidates. We also discuss possibilities to test such scenarios.

A decaying neutralino as dark matter and its gamma ray spectrum

It is shown that a decaying neutralino in a supergravity unified framework is a viable candidate for dark matter. Such a situation arises in the presence of a hidden sector with ultraweak couplings to the visible sector where the neutralino can decay into the hidden sector’s lightest supersymmetric particle (LSP) with a lifetime larger than the lifetime of the universe. We present a concrete model where the MSSM/SUGRA is extended to include a hidden sector comprised of $$U(1)_{X_1} \times U(1)_{X_2}$$ U ( 1 ) X 1 × U ( 1 ) X 2 gauge sector and the LSP of the hidden sector is a neutralino which is lighter than the LSP neutralino of the visible sector. We compute the loop suppressed radiative decay of the visible sector neutralino into the neutralino of the hidden sector and show that the decay can occur with a lifetime larger than the age of the universe. The decaying neutralino can be probed by indirect detection experiments, specifically by its signature decay into the hidden sector neutralino and an energetic gamma ray photon. Such a gamma ray can be searched for with improved sensitivity at Fermi-LAT and by future experiments such as the Square Kilometer Array (SKA) and the Cherenkov Telescope Array (CTA). We present several benchmarks which have a natural suppression of the hadronic channels from dark matter annihilation and decays and consistent with measurements of the antiproton background.

Chiral composite asymmetric dark matter

The asymmetric dark matter (ADM) scenario solves the baryon-dark matter coincidence problem when the dark matter (DM) mass is of $$ \mathcal{O}(1) $$ O 1 GeV. Composite ADM models based on QCD-like strong dynamics are particularly motivated since the strong dynamics naturally provides the DM mass of $$ \mathcal{O}(1) $$ O 1 GeV and the large annihilation cross-section simultaneously. In those models, the sub-GeV dark photon often plays an essential role in transferring the excessive entropy in the dark sector into the visible sector, i.e., the Standard Model sector. This paper constructs a chiral composite ADM model where the U(1)D gauge symmetry is embedded into the chiral flavor symmetry. Due to the dynamical breaking of the chiral flavor symmetry, the model naturally provides the masses of the dark photon and the dark pions in the sub-GeV range, both of which play crucial roles for a successful ADM model.