We present new measurements of the scintillation and ionization yields in liquid xenon for low energy electronic (about $3–7{\mathrm{keV}}_{ee}$) and nuclear recoils (about $8–20{\mathrm{keV}}_{nr}$) at different drift fields from $236\mathrm{V}/\mathrm{cm}$ to $3.93\mathrm{kV}/\mathrm{cm}$, using a three-dimensional sensitive liquid xenon time projection chamber with high energy and position resolutions. Our measurement of signal responses to nuclear recoils agrees with predictions from the NEST model. However, our measured ionization (scintillation) yields for electronic recoils are consistently higher (lower) than those from the NEST model by about $5{\mathrm{e}}^{-}/{\mathrm{keV}}_{ee}$ ($\mathrm{ph}/{\mathrm{keV}}_{ee}$) at all scanned drift fields. New recombination parameters based on the Thomas-Imel box model are derived from our data. Given the lack of precise measurement of scintillation and ionization yields for low energy electronic recoils in liquid xenon previously, our new measurement provides so far the best available data covering low energy regions at different drift fields for liquid xenon detectors relevant to dark matter searches.

• Received 4 May 2015

DOI:https://doi.org/10.1103/PhysRevD.92.032005