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We propose the lightest supersymmetric particle (LSP) as a well-suited candidate for superheavy dark matter (SHDM). Various production mechanisms at the end of inflation can produce SHDM with the correct abundance, $Omega_{LSP} h^2 sim 0.1$, if its mass is sufficiently high. In particular, gravitational production requires that the mass $m_{LSP}$ of the LSP is above $3times 10^{11} GeV$. Weak interactions remain perturbative despite the large mass hierarchy, $m_{LSP}gg m_Z$, because of the special decoupling properties of supersymmetry. As a result the model is predictive and we discuss the relevant cosmological processes for the case of a superheavy neutralino within this scheme.
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Although it is usually thought that a class of weakly interacting massive particle (WIMP) dark matters (DMs), which have the vector coupling with the $Z$ boson, is denied by null results of the direct DM searches, such WIMP DMs are still viable if they are superheavy with the mass of $m_{DM} gtrsim 10^9$ GeV. In the future, the superheavy WIMP DMs can be searched up to $m_{DM} simeq 10^{12}$ GeV, which corresponds to the so-called neutrino floor limit. We show that the observed abundance of $Omega_mathrm{DM}h^2 simeq 0.1$ for a superheavy WIMP DM can be reproduced by a suitable reheating temperature of $T_R simeq m_{DM}/29$ after inflation, if the direct inflaton decay into DM is negligible or kinematically forbidden.
We study the superheavy dark matter (DM) scenario in an extended $B-L$ model, where one generation of right-handed neutrino $ u_R$ 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 ($sim10^5$ GeV). We demonstrate that a DM mass $M_{ u_R}gtrsim10^{13}$ 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 $mathcal{O}(10^9-10^{13}~{rm GeV})$ can be probed by future GW detectors.
Different mechanisms operate in various regions of the MSSM parameter space to bring the relic density of the lightest neutralino, neutralino_1, assumed here to be the LSP and thus the Dark Matter (DM) particle, into the range allowed by astrophysics and cosmology. These mechanisms include coannihilation with some nearly-degenerate next-to-lightest supersymmetric particle (NLSP) such as the lighter stau (stau_1), stop (stop_1) or chargino (chargino_1), resonant annihilation via direct-channel heavy Higgs bosons H/A, the light Higgs boson h or the Z boson, and enhanced annihilation via a larger Higgsino component of the LSP in the focus-point region. These mechanisms typically select lower-dimensional subspaces in MSSM scenarios such as the CMSSM, NUHM1, NUHM2 and pMSSM10. We analyze how future LHC and direct DM searches can complement each other in the exploration of the different DM mechanisms within these scenarios. We find that the stau_1 coannihilation regions of the CMSSM, NUHM1, NUHM2 can largely be explored at the LHC via searches for missing E_T events and long-lived charged particles, whereas their H/A funnel, focus-point and chargino_1 coannihilation regions can largely be explored by the LZ and Darwin DM direct detection experiments. We find that the dominant DM mechanism in our pMSSM10 analysis is chargino_1 coannihilation: {parts of its parameter space can be explored by the LHC, and a larger portion by future direct DM searches.
Cosmological evolution and particle creation in $R^2$-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 $10^{12}$ GeV.
We show that supersymmetric Dark Force models with gravity mediation are viable. To this end, we analyse a simple string-inspired supersymmetric hidden sector model that interacts with the visible sector via kinetic mixing of a light Abelian gauge boson with the hypercharge. We include all induced interactions with the visible sector such as neutralino mass mixing and the Higgs portal term. We perform a detailed parameter space scan comparing the produced dark matter relic abundance and direct detection cross sections to current experiments.
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