1 The anisotropy parameter is basically the fractional difference between the rate of expansion in the preferred direction and that of a perpendicular direction. 2 I.e., the parameter g * (see equation (39)), as defined in [2], that characterizes the direction-dependence of the power spectrum due to a preferred direction is negative. 3 Both studies employed the δN formalism in calculating the curvature perturbation power spectra.

Summary and conclusions 35A Appendix: Additional model-selection results 40 B Appendix: Nuclear uncertainty 46 C Appendix: Astrophysical uncertainty 47 1. A broad class of available theoretical models (hypotheses) and corresponding phenomenologies for DM-nucleon scattering, discussed in §3. 2.A statistical representation of possible experimental outcomes, i.e. an ensemble of simulations that include Poisson noise, described in §4.3. An analysis framework for evaluating how well a given hypothesis "fits" a single data realization, as compared to other theories in consideration, detailed in §5.After introducing each of these prerequisites, we present the results of our analysis.The key results of this study are in Figures 8, 9, and 10. They show the following: G2 xenon and germanium targets (with several ton-year, and several hundred kilogram-year exposures, respectively) are sufficient to correctly identify the momentum dependence of the scattering cross section for a wide range of DM masses, if the signal is close to the current upper limit, regardless of the underlying scattering model. Thus, if a strong signal is seen with G2 experiments, we will be able to successfully discriminate between widely different phenomenologies (for example, the standard SI coupling of DM will be distinguishable from a dipole coupling, etc.). However, xenon and germanium on their own cannot generally distinguish amongst models that give rise to similar momentum and velocity dependence, even if novel nuclear responses contribute to the observed scattering rate. For this purpose, new targets with different spin and mass structure, such as iodine and fluorine, will be necessary. For example, ∼ 200 kilogram-years of exposure on an iodine target helps break degeneracies between a wide variety of theories that would otherwise be indistinguishable with xenon and germanium alone. We quantify these statements in detail in §6.Since this is the first study to explore model selection for a wide variety of well-motivated scattering models in a statistical way, we fix both the astrophysical and the nuclear-response models for DM-nuclear interactions in §5 and beyond. While our results make a case for a future comprehensive analysis including astrophysical and nuclear uncertainties, in §6, Appendix B, and Appendix C, we demonstrate arguments for optimism for model-selection results to be qualitatively robust with respect to these uncertainties.The rest of this paper is organized as follows. In §2, we present the basic definitions relevant for describing direct detection scattering. In §3, we assemble a representative list of DM-nucleon scattering operators. In §4 we describe our simulations of the recoil energy spectra under each of these scenarios. In §5 we describe the analysis of simulated data. In §6 we present and discuss our results. We summarize and conclude in §7. Appendix A includes a more complete set of results of model selection, a subset of which is presented in §6. Appendix B and Appendix C include a qualitative investigation of the ...

The landscape of dark matter direct detection has been profoundly altered by the slew of recent experiments. While some have claimed signals consistent with dark matter, others have seen few, if any, events consistent with dark matter. The results of the putative detections are often incompatible with each other in the context of naive spin-independent scattering, as well as with the null results. In particular, in light of the conflicts between the DM interpretation of the three events recently reported by the CDMS-Si experiment and the first results of the LUX experiment, there is a strong need to revisit the assumptions that go into the DM interpretations of both signals and limits. We attempt to reexamine a number of particle physics, astrophysics and experimental uncertainties. Specifically, we examine exothermic scattering, isospin-dependent couplings, modified halo models through astrophysics independent techniques, and variations in the assumptions about the scintillation light in liquid Xenon. We find that only a highly tuned isospin-dependent scenario remains as a viable explanation of the claimed detections, unless the scintillation properties of LXe are dramatically different from the assumptions used by the LUX experiment.

We examine the effect of nuclear response functions, as laid out in [1], on dark matter (DM) direct detection in the context of well-motivated UV completions, including electric and magnetic dipoles, anapole, spin-orbit, and pseudoscalar-mediated DM. Together, these encompass five of the six nuclear responses extracted from the non-relativistic effective theory of [1] (with the sixth difficult to UV complete), with two of the six combinations corresponding to standard spin-independent and -dependent responses. For constraints from existing direct detection experiments, we find that only the COUPP constraint, due to its heavy iodine target with large angular momentum and an unpaired spin, and its large energy range sensitivity, is substantially modified by the new responses compared to what would be inferred using the standard form factors to model the energy dependence of the response. For heavy targets such as xenon and germanium, the behavior of the new nuclear responses as recoil energy increases can be substantially different than that of the standard responses, but this has almost no impact on the constraints derived from experiments such as LUX, XENON100 and CDMS since the maximum nuclear recoil energy detected in these experiments is relatively low. We simulate mock data for 80 and 250 GeV DM candidates utilizing the new nuclear responses to highlight how they might affect a putative signal, and find the new responses are most important for momentum-suppressed interactions such as the magnetic dipole or pseudoscalar-mediated interaction when the target is relatively heavy (such as xenon and iodine).

Models of Asymmetric Dark Matter (ADM) with a sufficiently attractive and long-range force gives rise to stable bound objects, analogous to nuclei in the Standard Model, called nuggets. We study the properties of these nuggets and compute their profiles and binding energies. Our approach, applicable to both elementary and composite fermionic ADM, utilizes relativistic mean field theory, and allows a more systematic computation of nugget properties, over a wider range of sizes and force mediator masses, compared to previous literature. We identify three separate regimes of nugget property behavior corresponding to (1) non-relativistic and (2) relativistic constituents in a Coulomblike limit, and (3) saturation in an anti-Coulomb limit when the nuggets are large compared to the force range. We provide analytical descriptions for nuggets in each regime. Through numerical calculations, we are able to confirm our analytic descriptions and also obtain smooth transitions for the nugget profiles between all three regimes. We also find that over a wide range of parameter space, the binding energy in the saturation limit is an O(1) fraction of the constituent's mass, significantly larger than expectations in the non-relativistic case. In a companion paper, we apply our results to synthesis of ADM nuggets in the early Universe.