Speaker
Description
Direct-detection analyses typically assume the Standard Halo Model(SHM) with a Maxwell–Boltzmann distribution for the local galactic dark matter velocity, but deviations from this form and uncertainties in the velocity parameters must be quantified to reliably interpret experimental results. We carry out a systematic study of how these uncertainties propagate into single-phonon scattering rates, considering three benchmark halo models (SHM, Tsallis, and empirical) and four representative crystalline targets. Previous comparisons fixed the characteristic velocity across models, conflating shape differences with energy-scale differences. We instead introduce an rms-matching prescription that normalizes models to a common root-mean-square velocity. Under this prescription, the dominant source of uncertainty arises from the circular speed $v_\text{c}$, which controls the bulk of the distribution; differences in the velocity distribution function are subdominant compared to parameter variations within any single model. Uncertainties are largest at the lowest kinematically accessible dark matter masses and persist to higher masses for heavy mediators. For the daily modulation signal, parameter variations rescale the amplitude while leaving the phase robust across all halo model assumptions.