Identifying the theory of dark matter with direct detection
Identifying the true theory of dark matter depends crucially on accurately characterizing interactions of dark matter (DM) with other species. In the context of DM direct detection, we present a study of the prospects for correctly identifying the low-energy effective DM-nucleus scattering operators connected to UV-complete models of DM-quark interactions. We take a census of plausible UV-complete interaction models with different low-energy leading-order DM-nuclear responses. For each model (corresponding to different spin–, momentum–, and velocity-dependent responses), we create a large number of realizations of recoil-energy spectra, and use Bayesian methods to investigate the probability that experiments will be able to select the correct scattering model within a broad set of competing scattering hypotheses. We conclude that agnostic analysis of a strong signal (such as Generation-2 would see if cross sections are just below the current limits) seen on xenon and germanium experiments is likely to correctly identify momentum dependence of the dominant response, ruling out models with either "heavy" or "light" mediators, and enabling downselection of allowed models. However, a unique determination of the correct UV completion will critically depend on the availability of measurements from a wider variety of nuclear targets, including iodine or fluorine. We investigate how model-selection prospects depend on the energy window available for the analysis. In addition, we discuss accuracy of the DM particle mass determination under a wide variety of scattering models, and investigate impact of the specific types of particle-physics uncertainties on prospects for model selection.
Article funded by SCOAP. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 License. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received June 26, 2015. Revised October 22, 2015. Accepted December 13, 2015. Published December 29, 2015. VG is grateful for the support provided by the Friends of the Institute for Advanced Study in Princeton. MG was supported in part by the Murdock Charitable Trust and some of her work was performed at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1066293. SDM is supported by NSF PHY1316617. KZ is supported by the DoE under contract DE-AC02-05CH11231. The authors thank Timothy Morton, Mikhail Solon, and Hugh Lippincott for helpful discussions.
Submitted - 1506.04454.pdf