  We report angular correlation function (ACF) of Lyman Break Galaxies (LBGs)
with unprecedented statistical quality on the basis of 16,920 LBGs at z=4
detected in the 1 deg^2 sky of the Subaru/XMM-Newton Deep Field. The ACF
significantly departs from a power law, and shows an excess on small scale.
Particularly, the ACF of LBGs with i'<27.5 have a clear break between the small
and large-scale regimes at the angular separation of ~7'' whose projected
length corresponds to the virial radius of dark halos with a mass of 10^11-12
Mo, indicating multiple LBGs residing in a single dark halo. Both on small
(2''<theta<3'') and large (40''<theta<400'') scales, clustering amplitudes
monotonically increase with luminosity for the magnitude range of i'=24.5-27.5,
and the small-scale clustering shows a stronger luminosity dependence than the
large-scale clustering. The small-scale bias reaches b~10-50, and the outskirts
of small-scale excess extend to a larger angular separation for brighter LBGs.
The ACF and number density of LBGs can be explained by the cold dark matter
model.
