Global fits of the dark matter-nucleon effective interactions

TL;DR

This paper performs a comprehensive statistical analysis of dark matter-nucleon interactions, constraining multiple coupling constants using current direct detection data through Bayesian and frequentist methods.

Contribution

It introduces a multidimensional analysis of the effective dark matter-nucleon theory, comparing Bayesian and frequentist approaches with current experimental data.

Findings

Current data constrain spin-independent, spin-dependent, velocity, and momentum couplings.

Strong correlations exist between some coupling constants in null-result experiments.

Degeneracies in coupling constants are found in experiments claiming signals.

Abstract

The effective theory of isoscalar dark matter-nucleon interactions mediated by heavy spin-one or spin-zero particles depends on 10 coupling constants besides the dark matter particle mass. Here we compare this 11-dimensional effective theory to current observations in a comprehensive statistical analysis of several direct detection experiments, including the recent LUX, SuperCDMS and CDMSlite results. From a multidimensional scan with about 3 million likelihood evaluations, we extract the marginalized posterior probability density functions (a Bayesian approach) and the profile likelihoods (a frequentist approach), as well as the associated credible regions and confidence levels, for each coupling constant vs dark matter mass and for each pair of coupling constants. We compare the Bayesian and frequentist approach in the light of the currently limited amount of data. We find that current direct detection data contain sufficient information to simultaneously constrain not only the familiar spin-independent and spin-dependent interactions, but also the remaining velocity and momentum dependent couplings predicted by the dark matter-nucleon effective theory. For current experiments associated with a null result, we find strong correlations between some pairs of coupling constants. For experiments that claim a signal (i.e., CoGeNT and DAMA), we find that pairs of coupling constants produce degenerate results.