Interpreting Dark Matter Direct Detection Independently of the Local Velocity and Density Distribution

TL;DR

This paper shows how to extract particle physics information from dark matter direct detection data without assumptions on local dark matter velocity or density, using the positivity of the velocity distribution.

Contribution

It introduces a method to interpret direct detection signals independently of astrophysical uncertainties, revealing new insights into dark matter properties.

Findings

Deconvoluted recoil spectrum can be mimicked by any dark matter mass above a minimum.

A rise in the recoil spectrum indicates specific particle physics features like inelastic scattering.

Heavy dark matter can explain signals previously attributed to lighter particles.

Abstract

We demonstrate precisely what particle physics information can be extracted from a single direct detection observation of dark matter while making absolutely no assumptions about the local velocity distribution and local density of dark matter. Our central conclusions follow from a very simple observation: the velocity distribution of dark matter is positive definite, f(v) >= 0. We demonstrate the utility of this result in several ways. First, we show a falling deconvoluted recoil spectrum (deconvoluted of the nuclear form factor), such as from ordinary elastic scattering, can be "mocked up" by any mass of dark matter above a kinematic minimum. As an example, we show that dark matter much heavier than previously considered can explain the CoGeNT excess. Specifically, m_chi < m_Ge} can be in just as good agreement as light dark matter, while m_\chi > m_Ge depends on understanding the sensitivity of Xenon to dark matter at very low recoil energies, E_R ~ 6 keVnr. Second, we show that any rise in the deconvoluted recoil spectrum represents distinct particle physics information that cannot be faked by an arbitrary f(v). As examples of resulting non-trivial particle physics, we show that inelastic dark matter and dark matter with a form factor can both yield such a rise.