Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userTerrestrial Probes of Electromagnetically Interacting Dark Radiation
262
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study the possibility that dark radiation, sourced through the decay of dark matter in the late Universe, carries electromagnetic interactions. The relativistic flux of particles induces recoil signals in direct detection and neutrino experiments through its interaction with millicharge, electric/magnetic dipole moments, or anapole moment/charge radius. Taking the DM lifetime as 35 times the age of the Universe, as currently cosmologically allowed, we show that direct detection (neutrino) experiments have complementary sensitivity down to $epsilonsim 10^{-11}$ $(10^{-12})$, $d_chi/mu_chi sim 10^{-9},mu_B$ $(10^{-13}mu_B)$, and $a_chi/b_chi sim 10^{-2},{rm GeV}^{-2}$ $(10^{-8},{rm GeV}^{-2})$ on the respective couplings. Finally, we show that such dark radiation can lead to a satisfactory explanation of the recently observed XENON1T excess in the electron recoil signal without being in conflict with other bounds.
rate research
Read More
We consider a simple class of models where dark radiation has self-interactions and therefore does not free stream. Such dark radiation has no anisotropic stress (or viscosity), leaving a distinct signature on the CMB angular power spectrum. Specifically we study a possibility that hidden gauge bosons and/or chiral fermions account for the excess of the effective number of neutrino species. They have gauge interactions and remain light due to the unbroken hidden gauge symmetry, leading to Delta N_{rm eff} simeq 0.29 in some case.
We examine the cosmological and astrophysical signatures of a dark baryon, a neutral fermion that mixes with the neutron. As the mixing is through a higher-dimensional operator at the quark level, production of the dark baryon at high energies is enhanced so that its abundance in the early universe may be significant. Treating its initial abundance as a free parameter, we derive new, powerful limits on the properties of the dark baryon. Primordial nucleosynthesis and the cosmic microwave background provide strong constraints due to the inter-conversion of neutrons to dark baryons through their induced transition dipole, and due to late decays of the dark baryon. Additionally, neutrons in a neutron star could decay slowly to dark baryons, providing a novel source of heat that is constrained by measurements of pulsar temperatures. Taking all the constraints into account, we identify parameter space where the dark baryon can be a viable dark matter candidate and discuss promising avenues for probing it.
We propose a new class of dark matter models with unusual phenomenology. What is ordinary about our models is that dark matter particles are WIMPs, they are weakly coupled to the Standard Model and have weak scale masses. What is unusual is that they come in multiplets of a new dark non-Abelian gauge group with milli-weak coupling. The massless dark gluons of this dark gauge group contribute to the energy density of the universe as a form of weakly self-interacting dark radiation. In this paper we explore the consequences of having i.) dark matter in multiplets ii.) self-interacting dark radiation and iii.) dark matter which is weakly coupled to dark radiation. We find that i.) dark matter cross sections are modified by multiplicity factors which have significant consequences for collider searches and indirect detection, ii.) dark gluons have thermal abundances which affect the CMB as dark radiation. Unlike additional massless neutrino species the dark gluons are interacting and have vanishing viscosity and iii.) the coupling of dark radiation to dark matter represents a new mechanism for damping the large scale structure power spectrum. A combination of additional radiation and slightly damped structure is interesting because it can remove tensions between global $Lambda$CDM fits from the CMB and direct measurements of the Hubble expansion rate ($H_0$) and large scale structure ($sigma_8$).
We present models of resonant self-interacting dark matter in a dark sector with QCD, based on analogies to the meson spectra in Standard Model QCD. For dark mesons made of two light quarks, we present a simple model that realizes resonant self-interaction (analogous to the $phi$-K-K system) and thermal freeze-out. We also consider asymmetric dark matter composed of heavy and light dark quarks to realize a resonant self-interaction (analogous to the $Upsilon(4S)$-B-B system) and discuss the experimental probes of both setups. Finally, we comment on the possible resonant self-interactions already built into SIMP and ELDER mechanisms while making use of lattice results to determine feasibility.
Dark matter may self-interact through a continuum of low-mass states. This happens if dark matter couples to a strongly-coupled nearly-conformal hidden sector. This type of theory is holographically described by brane-localized dark matter interacting with bulk fields in a slice of 5D anti-de Sitter space. The long-range potential in this scenario depends on a non-integer power of the spatial separation, in contrast to the Yukawa potential generated by the exchange of a single 4D mediator. The resulting self-interaction cross section scales like a non-integer power of velocity. We identify the Born, classical and resonant regimes and investigate them using state-of-the-art numerical methods. We demonstrate the viability of our continuum-mediated framework to address the astrophysical small-scale structure anomalies. Investigating the continuum-mediated Sommerfeld enhancement, we demonstrate that a pattern of resonances can occur depending on the non-integer power. We conclude that continuum mediators introduce novel power-law scalings which open new possibilities for dark matter self-interaction phenomenology.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
