  We present newly derived stellar parameters and the detailed abundances of 19
elements of seven stars with small planets discovered by NASA's Kepler Mission.
Each star save one has at least one planet with a radius <= 1.6 R_Earth,
suggesting a primarily rocky composition. The stellar parameters and abundances
are derived from high signal-to-noise ratio, high-resolution echelle
spectroscopy obtained with the 10-m Keck I telescope and HIRES spectrometer
using standard spectroscopic techniques. The metallicities of the seven stars
range from -0.32 dex to +0.13 dex, with an average metallicity that is
subsolar, supporting previous suggestions that, unlike Jupiter-type giant
planets, small planets do not form preferentially around metal-rich stars. The
abundances of elements other than iron are in line with a population of
Galactic disk stars, and despite our modest sample size, we find hints that the
compositions of stars with small planets are similar to stars without known
planets and with Neptune-size planets, but not to those of stars with giant
planets. This suggests that the formation of small planets does not require
exceptional host-star compositions and that small planets may be ubiquitous in
the Galaxy. We compare our derived abundances (which have typical uncertainties
of <= 0.04 dex) to the condensation temperature of the elements; a correlation
between the two has been suggested as a possible signature of rocky planet
formation. None of the stars demonstrate the putative rocky planet signature,
despite at least three of the stars having rocky planets estimated to contain
enough refractory material to produce the signature, if real. More detailed
abundance analyses of stars known to host small planets are needed to verify
our results and place ever more stringent constraints on planet formation
models.
