Distance to Galactic globulars using the near-infrared magnitudes of RR
  Lyrae stars: IV. The case of M5 (NGC5904)
  We present new and accurate near-infrared (NIR) J, K-band time series data
for the Galactic globular cluster (GC) M5 = NGC5904. Data were collected with
SOFI at the NTT (71 J + 120 K images) and with NICS at the TNG (25 J + 22 K
images) and cover two orthogonal strips across the center of the cluster of
\approx 5 \times 10 arcmin^{2} each. These data allowed us to derive accurate
mean K-band magnitudes for 52 fundamental (RR_{ab}) and 24 first overtone
(RR_{c}) RR Lyrae stars. Using this sample of RR Lyrae stars, we find that the
slope of the K-band Period Luminosity (PLK) relation (-2.33 \pm 0.08) agrees
quite well with similar estimates available in the literature. We also find,
using both theoretical and empirical calibrations of the PLK relation, a true
distance to M5 of (14.44 \pm 0.02) mag. This distance modulus agrees very well
(1\sigma) with distances based on main sequence fitting method and on kinematic
method (14.44 \pm 0.41 mag, \citealt{rees_1996}), while is systematically
smaller than the distance based on the white dwarf cooling sequence (14.67 \pm
0.18 mag, \citealt{layden2005}), even if with a difference slightly larger than
1\sigma. The true distance modulus to M5 based on the PLJ relation (14.50 \pm
0.08 mag) is in quite good agreement with the distance based on the PLK
relation further supporting the use of NIR PL relations for RR Lyrae stars to
improve the precision of the GC distance scale.
