  The average near-infrared (K-band) luminosity of 238 Hipparcos red clump
giants is derived and then used to measure the distance to the Galactic center.
These Hipparcos red clump giants have been previously employed as I-band
standard candles. The advantage of the K-band is a decreased sensitivity to
reddening, and perhaps also a reduced systematic dependence on metallicity. In
order to investigate the latter, and also to refer our calibration to a known
metallicity zero-point, we restrict our sample of red clump calibrators to
those with abundances derived from high-resolution spectroscopic data. The mean
metallicity of the sample is [Fe/H] = -0.18 dex. The data are consistent with
no correlation between M_K and [Fe/H], and only weakly constrain the slope of
this relation. The luminosity function of the sample peaks at M_K = -1.61 +-
0.03 mag. Next, we assemble published optical and near-infrared photometry for
about 20 red clump giants in a Baade's Window field with a mean metallicity
nearly identical to that of the Hipparcos red clump. We derive the distance to
the Galactic center: R = 8.24 +- 0.42 kpc. The uncertainty in this distance
measurement is dominated by the small number of Baade's Window red clump giants
examined here [abridged].
