  In an effort to improve the utility of the helium burning red clump
luminosity as a distance indicator, we explore the sensitivity of the K-band
red clump absolute magnitude Mk(RC) to metallicity and age. We rely upon JK
photometry for 14 open clusters and two globulars from the 2nd Incremental Data
Release of the 2MASS Point Source Catalog. The distances, metallicities, and
ages of the open clusters are all on an internally consistent system, while the
K(RC) values are measured from the 2MASS data. For clusters younger than ~2
Gyr, Mk(RC) is insensitive to metallicity but shows a dependence on age. In
contrast, for clusters older than ~2 Gyr, Mk(RC) is influenced primarily by the
metallicity of the population and shows little or no dependence on the age.
Theoretical red clump models based on the formalism of Girardi et al. reinforce
this finding. Over comparable metallicity and age ranges, our average Mk(RC)
value is in accord with that based on solar-neighborhood red clump stars with
HIPPARCOS parallaxes. Lastly, we compute the distance to the open cluster NGC
2158 using our red clump calibration. Adopting an age of 1.6 +/- 0.2 Gyr and
[Fe/H] = -0.24 +/- 0.06, our calibration yields a distance of (m-M)v = 14.38
+/- 0.09.
