We show that direct dark matter detection experiments can distinguish between
pointlike and non-pointlike dark-matter candidates. The shape of the nuclear
recoil energy spectrum from pointlike dark-matter particles, e.g., neutralinos,
is determined by the velocity distribution of dark matter in the galactic halo
and by nuclear form factors. In contrast, typical cross sections of
non-pointlike dark matter, for example, Q-balls, have a new form factor, which
decreases rapidly with the recoil energy. Therefore, a signal from
non-pointlike dark matter is expected to peak near the experimental threshold
and to fall off rapidly at higher energies. Although the width of the signal is
practically independent of the dark matter velocity dispersion, its height is
expected to exhibit an annual modulation due to the changes in the dark matter
flux.Comment: 4 pages; minor changes, references adde
