Analysis of the theoretical bias in dark matter direct detection

Abstract

Fitting the model \A" to dark matter direct detection data, when the model that underlies the data is \B", introduces a theoretical bias in the t. We perform a quantitative study of the theoretical bias in dark matter direct detection, with a focus on assumptions regarding the dark matter interactions, and velocity distribution. We address this problem within the e ective theory of isoscalar dark matter-nucleon interactions mediated by a heavy spin-1 or spin-0 particle. We analyze 24 benchmark points in the parameter space of the theory, using frequentist and Bayesian statistical methods. First, we simulate the data of future direct detection experiments assuming a momentum/velocity dependent dark matternucleon interaction, and an anisotropic dark matter velocity distribution. Then, we t a constant scattering cross section, and an isotropic Maxwell-Boltzmann velocity distribution to the simulated data, thereby introducing a bias in the analysis. The best t values of the dark matter particle mass di er from their benchmark values up to 2 standard deviations. The best t values of the dark matter-nucleon coupling constant di er from their benchmark values up to several standard deviations. We conclude that common assumptions in dark matter direct detection are a source of potentially signi cant bias.