Figure 2

(a), Acceleration of a silicon test particle (nucleon number density 1.4 · 10³⁰ m⁻³) across the size regimes for χ de Broglie wavelength . For small particles (), the Born approximation holds and acceleration is proportional to nucleon number; for large particles (), the force is proportional to projected area and thus increases slower than the inertia. In the intermediate regime (), acceleration depends strongly upon the particle shape: for illustration we have chosen a spherical particle with an attractive interaction; the repulsive case is similar. Resonances, which distract from the main argument, have been smoothed by a few times their width. Similar plots are obtained for other de Broglie wavelengths and the limiting cases are unaffected. (b), Reduction in sinusoidal fringe visibility due to elastic collisions for a range of m_χ. Experiments with a similar geometry and path separation are indicated: state-of-the-art experiments have demonstrated 10⁴ nucleons²¹; an experiment with 10⁶ is proposed²²; and space-based ‘MAQRO’²³ will span the necessary range. For , the Born approximation for scattering χ particles is not well satisfied and further theoretical work is needed to fully describe the decoherence.