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Register a new userAstrophysical Searches and Constraints on Ultralight Bosonic Dark Matter
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Starting from the evidence that dark matter indeed exists and permeates the entire cosmos, various bounds on its properties can be estimated. Beginning with the cosmic microwave background and large scale structure, we summarize bounds on the ultralight bosonic dark matter (UBDM) mass and cosmic density. These bounds are extended to larger masses by considering galaxy formation and evolution, and the phenomenon of black hole superradiance. We then discuss the formation of different classes of UBDM compact objects including solitons/axion stars and miniclusters. Next, we consider astrophysical constraints on the couplings of UBDM to Standard Model particles, from stellar cooling (production of UBDM) and indirect searches (decays or conversion of UBDM). Throughout, there are short discussions of hints and opportunities in searching for UBDM in each area.
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It has been argued that the existence of old neutron stars excludes the possibility of non-annihilating light bosonic dark matter, such as that arising in asymmetric dark matter scenarios. If non-annihilating dark matter is captured by neutron stars, the density will eventually become sufficient for black hole formation. However, the dynamics of collapse is highly sensitive to dark-matter self-interactions. Repulsive self-interactions, even if extremely weak, can prevent black hole formation. We argue that self-interactions will necessarily be present, and estimate their strength in representative models. We also consider co-annihilation of dark matter with nucleons, which arises naturally in many asymmetric dark matter models, and which again acts to prevent black hole formation. We demonstrate how the excluded region of the dark-matter parameter space shrinks as the strength of such interactions is increased, and conclude that neutron star observations do not exclude most realistic bosonic asymmetric dark matter models.
Ultralight scalar dark matter can interact with all massive Standard Model particles through a universal coupling. Such a coupling modifies the Standard Model particle masses and affects the dynamics of Big Bang Nucleosynthesis. We model the cosmological evolution of the dark matter, taking into account the modifications of the scalar mass by the environment as well as the full dynamics of Big Bang Nucleosynthesis. We find that precision measurements of the helium-4 abundance set stringent constraints on the available parameter space, and that these constraints are strongly affected by both the dark matter environmental mass and the dynamics of the neutron freeze-out. Furthermore, we perform the analysis in both the Einstein and Jordan frames, the latter of which allows us to implement the model into numerical Big Bang Nucleosynthesis codes and analyze additional light elements. The numerical analysis shows that the constraint from helium-4 dominates over deuterium, and that the effect on lithium is insufficient to solve the lithium problem. Comparing to several other probes, we find that Big Bang Nucleosynthesis sets the strongest constraints for the majority of the parameter space.
We review the physics case for very weakly coupled ultralight particles beyond the Standard Model, in particular for axions and axion-like particles (ALPs): (i) the axionic solution of the strong CP problem and its embedding in well motivated extensions of the Standard Model; (ii) the possibility that the cold dark matter in the Universe is comprised of axions and ALPs; (iii) the ALP explanation of the anomalous transparency of the Universe for TeV photons; and (iv) the axion or ALP explanation of the anomalous energy loss of white dwarfs. Moreover, we present an overview of ongoing and near-future laboratory experiments searching for axions and ALPs: haloscopes, helioscopes, and light-shining-through-a-wall experiments.
Dwarf spheroidal galaxies are excellent systems to probe the nature of fermionic dark matter due to their high observed dark matter phase-space density. In this work, we review, revise and improve upon previous phase-space considerations to obtain lower bounds on the mass of fermionic dark matter particles. The refinement in the results compared to previous works is realised particularly due to a significantly improved Jeans analysis of the galaxies. We discuss two methods to obtain phase-space bounds on the dark matter mass, one model-independent bound based on Paulis principle, and the other derived from an application of Liouvilles theorem. As benchmark examples for the latter case, we derive constraints for thermally decoupled particles and (non-)resonantly produced sterile neutrinos. Using the Pauli principle, we report a model-independent lower bound of $m geq 0.18,mathrm{keV}$ at 68% CL and $m geq 0.13,mathrm{keV}$ at 95% CL. For relativistically decoupled thermal relics, this bound is strengthened to $m geq 0.59,mathrm{keV}$ at 68% CL and $m geq 0.41,mathrm{keV}$ at 95% CL, whilst for non-resonantly produced sterile neutrinos the constraint is $m geq 2.80,mathrm{keV}$ at 68% CL and $m geq 1.74,mathrm{keV}$ at 95% CL. Finally, the phase-space bounds on resonantly produced sterile neutrinos are compared with complementary limits from X-ray, Lyman-$alpha$ and Big Bang Nucleosynthesis observations.
The ATLAS and CMS experiments did not find evidence for Supersymmetry using close to 5/fb of published LHC data at a center-of-mass energy of 7 TeV. We combine these LHC data with data on B_s -> mu mu (LHCb experiment), the relic density (WMAP and other cosmological data) and upper limits on the dark matter scattering cross sections on nuclei (XENON100 data). The excluded regions in the constrained Minimal Supersymmetric SM (CMSSM) lead to gluinos excluded below 1270 GeV and dark matter candidates below 220 GeV for values of the scalar masses (m_0) below 1500 GeV. For large m_0 values the limits of the gluinos and the dark matter candidate are reduced to 970 GeV and 130 GeV, respectively. If a Higgs mass of 125 GeV is imposed in the fit, the preferred SUSY region is above this excluded region, but the size of the preferred region is strongly dependent on the assumed theoretical error.
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