  We observe with Keck/HIRES the z ~ 2.5 QSO triplet 1623+27 in order to
explore on the scale of a Megaparsec the spatial clustering of C IV absorbers
between adjacent sightlines. We find this signal to be significantly weaker
than the clustering in velocity on corresponding scales along single
sightlines, assuming that the relative velocity of absorbers is dominated by
the Hubble flow. This indicates that small-scale clustering (200 km/s < Delta v
< 600 km/s) of the C IV absorbers cannot be interpreted in terms of the
positions of the absorbers in space, but must be considered as internal motions
within individual absorbers, or within clusters of absorbers whose internal
velocities dominate over Hubble expansion across the cluster scale. If the
single- sightline signal is due to spatial clustering, it is caused by absorber
clusters smaller than would be implied by their velocities if a Hubble flow is
assumed. The spatial clustering of C IV absorbers at z ~ 2 is consistent with
data on Ly alpha forest clustering measured in the same way at the same
redshifts. However, present-day galaxy clustering, evolved back to z ~ 2, is
consistent with C IV spatial clustering but perhaps not with that of the Ly
alpha forest. Even so, one cannot as yet distinguish the two absorber
populations on the basis of spatial clustering on these small scales.
