BBN for the LHC: Constraints on lifetimes of the Higgs portal scalars

Traditional direct searches for dark matter, looking for nuclear recoils in deep underground detectors, are challenged by an almost complete loss of sensitivity for light dark matter particles. Consequently, there is a significant effort in the community to devise new methods and experiments to overcome these difficulties, constantly pushing the limits of the lowest dark matter mass that can be probed this way. From a model-building perspective, the scattering of sub-GeV dark matter on nucleons essentially must proceed via new light mediator particles, given that collider searches place extremely stringent bounds on contact-type interactions. Here we present an updated compilation of relevant limits for the case of a scalar mediator, including a new estimate of the near-future sensitivity of the NA62 experiment as well as a detailed evaluation of limits from Big Bang nucleosynthesis. We also derive updated and more general limits on DM particles upscattered by cosmic rays, applicable to arbitrary energy-and momentum dependences of the scattering cross section. Finally we stress that dark matter self-interactions place stringent limits independently of the dark matter production mechanism. These are, for the relevant parameter space, generically comparable to those that apply in the commonly studied freeze-out case. We conclude that the combination of existing (or expected) constraints from accelerators and astrophysics, combined with cosmological requirements, puts robust limits on the maximally possible nuclear scattering rate. In most regions of parameter space these are at least competitive with the best projected limits from currently planned direct detection experiments.arXiv:1909.08632v2 [hep-ph]

Section: Big Bang Nucleosynthesismentioning

confidence: 58%

“…The corresponding lifetime of the scalar depends on the available decay channels and we adopt the results from ref. [104] in the following.…”

Section: T > T Decmentioning

confidence: 99%

Direct detection and complementary constraints for sub-GeV dark matter

Bondarenko

Boyarsky

Bringmann

et al. 2020

“…The decay of S to SM particles is given by Γ(S → SM) = θ 2 Γ h→SM (m S,T ), where the Γ h→SM (m S,T ) is the total width of the SM-like Higgs boson with mass m S,T . We implement using the results taken from [34][35][36] and a direct evaluation for leptonic decay at low masses. 11 For example, this term can shift the thermal mass of S by a factor of O λ S v S µ S 2 .…”

Section: The Modelmentioning

confidence: 99%

Forbidden frozen-in dark matter

Hryczuk

Karamitros

Roszkowski

2019

We examine and point out the importance of a regime of dark matter production through the freeze-in mechanism that results from a large thermal correction to a decaying mediator particle mass from hot plasma in the early Universe. We show that mediator decays to dark matter that are kinematically forbidden at the usually considered ranges of low temperatures can be generically present at higher temperatures and actually dominate the overall dark matter production, thus leading to very distinct solutions from the standard case. We illustrate these features by considering a dark Higgs portal model where dark matter is produced via decays of a scalar field with a large thermal mass. We identify the resulting ranges of parameters that are consistent with the correct dark matter relic abundance and further apply current and expected future collider, cosmological, and astrophysical limits.

“…we find that the strongest bound comes from the electromagnetic fraction of these decays, because the abundance of ψ is too small to affect proton-neutron conversions at early stages of BBN [111], and the injected hadrons are not energetic enough for hadro-dissociation to affect primordial light element abundances [112,113].…”

Section: Jhep08(2018)079mentioning

confidence: 99%

Exponentially light dark matter from coannihilation

D’Agnolo

Mondino

Wang

et al. 2018

Dark matter may be a thermal relic whose abundance is set by mutual annihilations among multiple species. Traditionally, this coannihilation scenario has been applied to weak scale dark matter that is highly degenerate with other states. We show that coannihilation among states with split masses points to dark matter that is exponentially lighter than the weak scale, down to the keV scale. We highlight the regime where dark matter does not participate in the annihilations that dilute its number density. In this "sterile coannihilation" limit, the dark matter relic density is independent of its couplings, implying a broad parameter space of thermal relic targets for future experiments. Light dark matter from coannihilation evades stringent bounds from the cosmic microwave background, but will be tested by future direct detection, fixed target, and long-lived particle experiments.