lower panel of Fig. \[fig:pratio1\] shows the fraction of stars in the distinct populations as a function of the stellar mass, where the stellar masses are derived by using the mass-luminosity relation provided by the best-fit isochrones derived in Sect. \[subsec:theory\]. Results are consistent with constant fraction of population-A, -B and -C stars over the analyzed interval of $\sim0.15$-$0.80$ solar masses.

![Fractions of stars in the populations A (green), B (magenta), and C (blue) against radial distance from the cluster center (upper panel) and stellar mass (lower panel). The fractions of stars more massive than 0.5 solar masses are taken from Milone et al.(2013, 2017 circles) and Nardiello et al.(2015, squares), while the results for low-mass stars are derived in this paper and are represented with triangles. This figure suggests that there is no evidence for strong dependence between the population ratios and neither stellar mass nor radial distance.[]{data-label="fig:pratio1"}](f5.ps){width="8.7cm"}

Summary and discussion {#sec:discussion}
======================

In the context of the [*HST*]{} Large program on NGC6752 (GO-15096), we analyzed deep WFC3/NIR photometry to investigate multiple stellar populations among M-dwarfs in NGC6752. The $m_{\rm F160W}$ vs.$m_{\rm F110W}-m_{\rm F160W}$ CMD of NGC6752 reveals that the MS splits into three distinct sequences below the MS 