  Hadron emission from supernova remnant (SNR)-molecular cloud (MC) association
systems has been widely regarded as a probe of the shock-accelerated cosmic-ray
protons. Here, we report on the detection of a {\gamma}-ray emission source,
with a significance of 24{\sigma} in 0.2-300 GeV, projected to lie to the
northwest of the thermal composite SNR Kesteven 41, using 5.6 years of
Fermi-Large Area Telescope (LAT) observation data. No significant long-term
variability in the energy range 0.2--300 GeV is detected around this source.
The 3{\sigma} error circle, 0.09 degree; in radius, covers the 1720MHz OH maser
and is essentially consistent with the location of the V_{LSR} ~-50 km/s MC
with which the SNR interacts. The source emission has an exponential cutoff
power-law spectrum with a photon index of 1.9+/-0.1 and a cutoff energy of
4.0+/-0.9 GeV, and the corresponding 0.2-300 GeV luminosity is ~1.3*10^36 erg/s
at a distance of 12 kpc. There is no radio pulsar in the 3{\sigma} circle
responsible for the high {\gamma}-ray luminosity. While the inverse Compton
scattering scenario would lead to a difficulty in the electron energy budget,
the source emission can naturally be explained by the hadronic interaction
between the relativistic protons accelerated by the shock of SNR Kesteven 41
and the adjacent northwestern MC. In this paper, we present a list of Galactic
thermal composite SNRs detected at GeV {\gamma}-ray energies by Fermi-LAT is
presented.
