  We report the results of a six-month Swift monitoring campaign of Ark120, a
prototypical bare Seyfert1 galaxy. The lack of intrinsic absorption combined
with the nearly contemporaneous coverage of the UV and X-ray bands makes it
possible to investigate the link between the accretion disk and the
Comptonization corona. Our observations confirm the presence of substantial
temporal variability, with the X-rays characterized by large-amplitude flux
changes on timescales of few days, while the variations in the UV bands are
smoother on timescales of several weeks. The source also shows spectral
variability with the X-ray spectrum steepening when the source is brighter. We
do not detect any correlation between the UV flux and the X-ray spectral slope.
A cross correlation analysis suggests positive delays between X-rays and the UV
emission, favoring a scenario of disk reprocessing. Although the strength of
the correlation is moderate with a delay not well constrained (7.5+-7 days), it
is nevertheless indicative of a large disk reprocessing region, with a
separation between the X-ray and the UV emitting regions of the order of 1000
rG. The Ark120 correlation results are in agreement with those obtained in
similar monitoring studies. When combined together, the observations can be
well described by a linear relation between the X-ray/UV delay and the black
hole mass. Within the context of the simplest scenario where these delays
correspond to light-travel times, the implied distance between the X-ray source
and the UV disk reprocessing region is of the order of many hundreds of
gravitational radii.
