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We carry out an independent search of Kepler photometry for small transitingplanets with sizes 0.5--8.0 times that of Earth and orbital periods between 5and 50 days, with the goal of measuring the fraction of stars harboring suchplanets. We use a new transit search algorithm, TERRA, optimized to detectsmall planets. We restrict our stellar sample to include the 12,000 starshaving the lowest photometric noise in the Kepler survey. We report 129 planetcandidates having radii less than 6 Earth-radii found in 3 years of Keplerphotometry. Forty-seven of these candidates are not in Batalha et al. (2012).We gather Keck HIRES spectra for the majority of these targets leading toprecise stellar radii and hence precise planet radii. We inject syntheticdimmings from mock transiting planets into the actual Kepler photometry andanalyze that photometry with TERRA to assess detection completeness. We computethe occurrence of planets as a function of planet radius and period, correctingfor the detection completeness. The resulting distribution of planet sizesexhibits a power law rise in occurrence from 5.7 Earth-radii down to 2Earth-radii, as found in Howard et al. (2012). That rise clearly ends at 2Earth-radii. The occurrence of planets is consistent with constant from 2Earth-radii toward 1 Earth-radius. This unexpected plateau in planet occurrenceat 2 Earth-radii suggests distinct planet formation processes for planets aboveand below 2 Earth-radii. We find 15.1% of solar type stars---roughly one insix---has a 1--2 Earth-radii planet with P = 5--50 days.

A Plateau in the Planet Population Below Twice the Size of Earth