Closing the window on WIMP Dark Matter

Abstract

We study scenarios where Dark Matter is a weakly interacting particle (WIMP) embedded in an ElectroWeak multiplet. In particular, we consider real SU(2) representations with zero hypercharge, that automatically avoid direct detection constraints from tree-level Z-exchange. We compute for the first time all the calculable thermal masses for scalar and fermionic WIMPs, including Sommerfeld enhancement and bound states formation at leading order in gauge boson exchange and emission. WIMP masses of few hundred TeV are shown to be compatible both with s-wave unitarity of the annihilation cross-section, and perturbativity. We also provide theory uncertainties on the masses for all multiplets, which are shown to be significant for large SU(2) multiplets. We then outline a strategy to probe these scenarios at future experiments. Electroweak 3-plets and 5-plets have masses up to about 16 TeV and can efficiently be probed at a high energy muon collider. We study various experimental signatures, such as single and double gauge boson emission with missing energy, and disappearing tracks, and determine the collider energy and luminosity required to probe the thermal Dark Matter masses. Larger multiplets are out of reach of any realistic future collider, but can be tested in future $$\gamma $$ γ -ray telescopes and possibly in large-exposure liquid Xenon experiments.

Saha equilibrium for metastable bound states and dark matter freeze-out

“…The formation of metastable bound states and their subsequent decays into radiation open new annihilation channels for DM that can significantly reduce its predicted relic density [3]. Besides being supported by unitarity arguments, the emergence of this type of inelasticity in the multi-TeV regime has been shown by explicit calculations in a variety of theories [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. In addition to DM freeze-out, its implications extend to DM indirect detection and collider signatures, as discussed in the original works of ref.…”

“…The reason has been two-fold: the capture into the ground state is indeed dominant in some models [51][52][53], while excited states tend to decay into radiation more slowly and be ionised rapidly until lower temperatures than the ground state, when the DM density is smaller, which limits their efficacy in depleting the DM abundance. However, recent studies have shown that this does not hold in general; capture into excited states can be faster than into the ground state, while de-excitations increase (decrease) the effective decay (ionisation) rate of the excited states [15,[19][20][21]. Considering excited levels is hence crucial for predicting the DM density accurately [20,21].…”

Revisiting the Fermionic Dark Matter Absorption on Electron Target

“…where K 1 is the first modified Bessel function of second kind and s ≡ (p e − + p e + ) 2 is the electron positron invariant mass squared. The solution of the Boltzmann equation in (11) can be obtained by integrating the temperature T from neutrino decoupling T max ≈ 1 MeV,…”

“…With typical experimental threshold at O(1) keV, direct detection experiments are only sensitive to the DM mass above GeV. In the GeV∼TeV mass range, the null result from the direct detection experiments has put very strong limit on the DM interaction strength with the Standard Model (SM) particles [10,11]. In contrast, the cross section of sub-GeV light DM scattering with SM particles is much less stringently constrained and can still be large [3,4].…”

Operation and performance of a dual-phase crystalline/vapor xenon time projection chamber

“…However, they will be limited by radon backgrounds rather than the irreducible neutrino flux from solar, atmospheric and diffuse cosmic sources [3,4]. Whatever the experimental outcome -improved exclusion limits, a few tantalizing events, or a dark matter signal detection -there will be strong motivation to reach the irreducible neutrino detection limit [5]. Removing radon-related backgrounds would result in an experiment with neutrinos as the dominant background.…”