  We provide homogeneous optical (UBVRI) and near-infrared (JHK) time series
photometry for 254 cluster (omega Cen, M4) and field RR Lyrae (RRL) variables.
We ended up with more than 551,000 measurements. For 94 fundamental (RRab) and
51 first overtones (RRc) we provide a complete optical/NIR characterization
(mean magnitudes, luminosity amplitudes, epoch of the anchor point). The NIR
light curves of these variables were adopted to provide new and accurate
light-curve templates for both RRc (single period bin) and RRab (three period
bins) variables. The templates for the J and the H band are newly introduced,
together with the use of the pulsation period to discriminate among the
different RRab templates. To overcome subtle uncertainties in the fit of
secondary features of the light curves we provide two independent sets of
analytical functions (Fourier series, Periodic Gaussian functions). The new
templates were validated by using 26 omega Cen and Bulge RRLs covering the four
period bins. We found that the difference between the measured mean magnitude
along the light curve and the mean magnitude estimated by using the template on
a single randomly extracted phase point is better than 0.01 mag (sigma=0.04
mag). We also validated the template on variables for which at least three
phase points were available, but without information on the phase of the anchor
point. The accuracy of the mean magnitudes is ~0.01 mag (sigma=0.04 mag). The
new templates were applied to the Large Magellanic Cloud (LMC) globular
Reticulum and by using literature data and predicted PLZ relations we found
true distance moduli of 18.47+-0.10+-0.03 mag (J) and 18.49+-0.09+-0.05 mag
(K). We also used literature optical and mid-infrared data and we found a mean
true distance modulus of 18.47+-0.02+-0.06 mag, suggesting that Reticulum is ~1
kpc closer than the LMC.
