Probing superheavy dark matter with gravitational waves

We study the superheavy dark matter (DM) scenario in an extended B−L model, where one generation of right-handed neutrino νR is the DM candidate. If there is a new lighter sterile neutrino that co-annihilate with the DM candidate, then the annihilation rate is exponentially enhanced, allowing a DM mass much heavier than the Griest-Kamionkowski bound (∼105 GeV). We demonstrate that a DM mass MνR ≳ 1013 GeV can be achieved. Although beyond the scale of any traditional DM searching strategy, this scenario is testable via gravitational waves (GWs) emitted by the cosmic strings from the U(1)B−L breaking. Quantitative calculations show that the DM mass $$ \mathcal{O} $$ O (109−1013 GeV) can be probed by future GW detectors.

R2-Cosmology and New Windows for Superheavy Dark Matter

Evolution and heating of the universe in R2-modified gravity are considered. It is shown that the universe’s history can be separated into four different epochs: (1) inflation, (2) heating due to curvature oscillations (scalaron decay), (3) transition to matter dominated period, and (4) conventional cosmology governed by General Relativity. Cosmological density of dark matter (DM) particles for different decay channels of the scalaron is calculated. The bounds on the masses of DM particles are derived for the following dominant decay modes: to minimally coupled scalars, to massive fermions, and to gauge bosons.

Superheavy dark matter in R2-cosmology

The conventional Friedmann cosmology is known to be in tension with the existence of stable particles having interaction strength typical for supersymmetry and heavier than several TeV. A possible way to save life of such particles may be a modification of the standard cosmological expansion law in such a way that the density of these heavy relics would be significantly reduced. We study particle creation in the Starobinsky inflationary model for different decay channels of the scalaron. It is shown that the process of thermalization superheavy stable particles with the coupling strength typical for the GUT SUSY could be created with the density equal to the observed density of dark matter.

Direct measurement of upward-going ultrahigh energy dark matter at the Pierre Auger Observatory

It is assumed that two types of dark matter particles exist: superheavy dark matter particles (SHDM), the mass of which ∼ inflaton mass, and light fermion dark matter (DM) particles, which are the ultrahigh energy (UHE) products of the decay of SHDM. The Earth will be taken as a detector to search for the UHE DM particles directly. These upward-going particles, which pass through the Earth and air and interact with nuclei, can be detected by the fluorescence detectors (FD) of the Pierre Auger Observatory (Auger), via fluorescent photons due to the development of an extensive air shower. The numbers and fluxes of expected UHE DM particles are evaluated in the incoming energy range between 1 EeV and 1 ZeV with the different lifetimes of decay of SHDM and mass of Z′. According to the Auger data from 2008 to 2019, the upper limit for UHE DM fluxes is also estimated at 90% confidence limit with the FD of Auger. Finally, it is reasonable to make a conclusion that UHE DM particles could be directly detected in the energy range between O(1 EeV) and O(10 EeV) with the FD of Auger. This might prove whether SHDM particles exist in the Universe.

Superheavy dark matter from string theory

Explicit string models which can realize inflation and low-energy supersymmetry are notoriously difficult to achieve. Given that sequestering requires very specific configurations, supersymmetric particles are in general expected to be very heavy implying that the neutralino dark matter should be overproduced in a standard thermal history. However, in this paper we point out that this is generically not the case since early matter domination driven by string moduli can dilute the dark matter abundance down to the observed value. We argue that generic features of string compactifications, namely a high supersymmetry breaking scale and late time epochs of modulus domination, might imply superheavy neutralino dark matter with mass around 1010–1011 GeV. Interestingly, this is the right range to explain the recent detection of ultra-high-energy neutrinos by IceCube and ANITA via dark matter decay.

Superheavy dark matter in $$R+R^2$$ cosmology with conformal anomaly

Cosmological evolution and particle creation in $$R^2$$ R 2 -modified gravity are considered for the case of the dominant decay of the scalaron into a pair of gauge bosons due to conformal anomaly. It is shown that in the process of thermalization superheavy dark matter with the coupling strength typical for the GUT SUSY can be created. Such dark matter would have the proper cosmological density if the particle mass is close to $$10^{12}$$ 10 12 GeV.