Effective Field Theory of Dark Matter Direct Detection With Collective Excitations

Abstract

We develop a framework for computing light dark matter direct detection rates through single phonon and magnon excitations via general effective operators. Our work generalizes previous calculations focused on spin-independent interactions involving the total nucleon and electron numbers N (the usual route to excite phonons) and spin-dependent interactions involving the total electron spin S (the usual route to excite magnons), leading us to identify new responses involving the orbital angular momenta L, as well as spin-orbit couplings L⊗S in the target. All four types of responses can excite phonons, while couplings to electron's S and L can also excite magnons. We apply the effective field theory approach to a set of wellmotivated relativistic benchmark models, including (pseudo-)scalar mediated interactions, and models where dark matter interacts via a multipole moment, such as a dark electric dipole, magnetic dipole or anapole moment. We find that couplings to point-like degrees of freedom N and S often dominate dark matter detection rates, implying that exotic materials with orbital L order or large spin-orbit couplings L⊗S are not necessary to have strong reach to a broad class of DM models. We also highlight that phonon based crystal experiments in active R&D (such as SPICE) will probe light dark matter models well beyond those having a simple spin-independent interaction, including e.g. models with dipole and anapole interactions.

Atomic responses to general dark matter-electron interactions

“…Our formalism is based on an effective theory approach to nonrelativistic DM-electron interactions, and a set of crystal response functions defined in terms of electron wave function overlap integrals. Effective theory methods have previously been used in the scattering of DM particles by nuclei [44,45], in modelling collective excitations in DM direct detection experiments [46] and in a study of the DM scattering by bound electrons in isolated atomic systems [41]. This latter work introduced the notion of "atomic response" to DM-electron interactions that we here extend to the case of semiconductor crystals.…”

Dark Sound

“…. ' refers to other matter couplings [18]. The non-gravitational couplings are all small because they are controlled by inverse powers of the axion energy scale f a , which is constrained by experiment to be very large: f a 10 7 GeV [9].…”

The Phonon Background from Gamma Rays in Sub-GeV Dark Matter Detectors

“…Growing efforts to directly detect non-gravitational particlelike interactions of DM with masses lighter than the proton have inspired a multitude of upcoming and expanding experiments over the last decade . One promising such direction is the use of semiconductor detectors, which can be sensitive to light DM in the 10 keV − 100 MeV mass range through electron and phonon signals (see, e.g., [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]). Characterizing, quantifying, and mitigating the backgrounds in these experiments is a crucial task to ensure their success [51][52][53].…”