Weakly interacting massive particle annual modulation with opposite phase in late-infall halo models

We show that in the late-infall model of our galactic halo of Sikivie the expected phase of the annual modulation of a weakly interacting massive particle (WIMP) halo signal in direct detection experiments is opposite to the one usually expected. If a nonvirialized halo component due to the infall of (collisionless) dark matter particles cannot be rejected, an annual modulation in a dark matter signal should be looked for by experimenters without fixing the phase a priori. Moreover, WIMP streams coming to Earth from directions above and below the galactic plane should be expected, with a characteristic pattern of arrival directions.