Multichannel direct detection of light dark matter: Target comparison

Abstract

Direct detection experiments for light dark matter are making enormous leaps in reaching previously unexplored model space. Several recent proposals rely on collective excitations, where the experimental sensitivity is highly dependent on detailed properties of the target material, well beyond just nucleus mass numbers as in conventional searches. It is thus important to optimize the target choice when considering which experiment to build. We carry out a comparative study of target materials across several detection channels, focusing on electron transitions and single (acoustic or optical) phonon excitations in crystals, as well as the traditional nuclear recoils. We compare materials currently in use in nuclear recoil experiments (Si, Ge, NaI, CsI, CaWO4), a few which have been proposed for light dark matter experiments (GaAs, Al2O3, diamond), as well as 16 other promising polar crystals across all detection channels. We find that target-and dark matter modeldependent reach is largely determined by a small number of material parameters: speed of sound, electronic band gap, mass number, Born effective charge, high frequency dielectric constant, and optical phonon energies. We showcase, for each of the two benchmark models, an exemplary material which has a better reach than in any currently proposed experiment.

Dark matter interpretation of excesses in multiple direct detection experiments

“…(3) In an anisotropic material where plasmon-phonon interactions or the dielectric function are directional, a daily modulation may be seen. In the direct excitation model, there may also be strong directional signals in low-threshold experiments searching for the dominant 1 − f cold DM fraction [46,[100][101][102][103]. (4) The secondary plasmon hypothesis from Sec.…”

Dark matter substructure under the electron scattering lamppost

“…[53,54] for a fast, benchmarkfree calculation of Eq. (15). For more details on how the ES method is implemented in context of direct detection experiments, we refer the reader to Refs.…”

“…Traditional nuclear recoil experiments [1][2][3][4][5][6] are pushing the limits on the DM interaction cross section toward the neutrino floor for heavy DM particles, whereas electron recoil experiments [7][8][9][10][11][12][13][14] are probing increasingly smaller DM masses. For a comparison of different targets for sub-GeV DM direct detection, see [15].…”

Plasmon production from dark matter scattering

“…As experiments lower their energy thresholds, collective many-body effects can become increasingly important and enhance the discovery potential beyond that of traditional searches for hard nuclear recoils. Examples can be found in numerous theoretical studies of direct detection of sub-GeV dark matter, including with semiconductors [2][3][4][5], superconductors [6][7][8], Dirac materials [9][10][11][12][13], phonon excitations in crystals [14][15][16][17], phonons in superfluid He [18][19][20], and others.…”