  We present a multi-wavelength analysis of 48 submillimeter galaxies (SMGs)
detected in the LABOCA/ACT Survey of Clusters at All Redshifts, LASCAR, which
acquired new 870 $\mu$m and ATCA 2.1 GHz observations of ten galaxy clusters
detected through their Sunyaev-Zel'dovich effect (SZE) signal by the Atacama
Cosmology Telescope. Far-infrared observations were also conducted with the
PACS (100/160 $\mu$m) and SPIRE (250/350/500 $\mu$m) instruments on $Herschel$
for sample subsets of five and six clusters. LASCAR 870 $\mu$m, maps were
reduced using a multi-scale iterative pipeline that removes the SZE increment
signal, yielding point-source sensitivities of
$\sigma\sim2\rm{\,mJy\,beam}^{-1}$. We detect in total 49 sources at the
$4\sigma$ level, and conduct a detailed multi-wavelength analysis considering
our new radio and far-IR observations plus existing near-IR and optical data.
One source is identified as a foreground galaxy, 28 SMGs are matched to single
radio sources, 4 have double radio counterparts, and 16 are undetected at 2.1
GHz but tentatively associated in some cases to near-IR/optical sources. We
estimate photometric redshifts for 34 sources with secure (25) and tentative
(9) matches at different wavelengths, obtaining a median $z=2.8^{+2.1}_{-1.7}$.
Compared to previous results for single-dish surveys, our redshift distribution
has a comparatively larger fraction of sources at $z>3$ and the high-redshift
tail is more extended. This is consistent with millimeter spectroscopic
confirmation of a growing number of high-$z$ SMGs and relevant for testing of
cosmological models. Analytical lens modeling is applied to estimate
magnification factors for 42 SMGs at cluster-centric radii $>1.2$'; with the
demagnified flux densities and source-plane areas, we obtain integral number
counts that agree with previous submillimeter surveys.
