  Observations of strong gravitational lensing, stellar kinematics, and
larger-scale tracers enable accurate measures of the distribution of dark
matter (DM) and baryons in massive early-type galaxies (ETGs). While such
techniques have been applied to galaxy-scale and cluster-scale lenses, the
paucity of intermediate-mass systems with high-quality data has precluded a
uniform analysis of mass-dependent trends. With the aim of bridging this gap,
we present new observations and analyses of 10 group-scale lenses at <z>=0.36
characterized by Einstein radii theta_Ein=2.5"-5.1" and a mean halo mass of
M_200=10^14.0 Msol. We measure a mean concentration c_200=5.0+-0.8 consistent
with unmodified cold dark matter halos. By combining our data with other lens
samples, we analyze the mass structure of ETGs in 10^13 Msol-10^15 Msol halos
using homogeneous techniques. We show that the slope of the total density
profile gamma_tot within the effective radius depends on the stellar surface
density, as demonstrated previously, but also on the halo mass. We analyze
these trends using halo occupation models and resolved stellar kinematics with
the goal of testing the universality of the DM profile. Whereas the central
galaxies of clusters require a shallow inner DM density profile, group-scale
lenses are consistent with a Navarro-Frenk-White profile or one that is
slightly contracted. The largest uncertainties arise from the sample size and
likely radial gradients in stellar populations. We conclude that the net effect
of baryons on the DM distribution may not be universal, but more likely varies
with halo mass due to underlying trends in star formation efficiency and
assembly history.
