  We present the results of an 850 micron JCMT/SCUBA survey for dust around 13
nearby solar mass stars. The dust mass sensitivity ranged from 0.005 to 0.16
Earth masses. Three sources were detected in the survey, one of which (HD
107146) has been previously reported. One of the other two submillimeter
sources, HD 104860, was not detected by IRAS and is surrounded by a cold,
massive dust disk with a dust temperature and mass of Tdust = 33 K and Mdust =
0.16 Mearth. The third source, HD 8907, was detected by IRAS and ISO at 60-87
microns, and has a dust temperature and mass Tdust = 48 K and Mdust = 0.036
Mearth. We find that the deduced masses and radii of the dust disks in our
sample are roughly consistent with models for the collisional evolution of
planetesimal disks with embedded planets. We also searched for residual gas in
two of the three systems with detected submillimeter excesses and place limits
on the mass of gas residing in these systems.
  When the properties measured for the detected excess sources are combined
with the larger population of submillimeter excess sources from the literature,
we find strong evidence that the mass in small grains declines significantly on
a ~200 Myr timescale, approximately inversely with age. However, we also find
that the characteristic dust radii of the population, obtained from the dust
temperature of the excess and assuming blackbody grains, is uncorrelated with
age. This is in contrast to self-stirred collisional models for debris disk
evolution which predict a trend of radius increasing with age, t ~ R^3. The
lack of agreement suggests that processes beyond self-stirring, such as giant
planet formation, play a role in the evolutionary histories of planetesimal
disks.
