Depth of shower maximum and mass composition of cosmic rays from 50 PeV to 2 EeV measured with the LOFAR radio telescope

We present an updated cosmic-ray mass composition analysis in the energy range $10^{16.8}$ to $10^{18.3}$ eV from 334 air showers measured with LOFAR radio telescope, and selected for minimal bias. In this range, origin of cosmic rays is expected shift galactic extragalactic sources. The based on improved method infer depth maximum $X_{\rm max}$ extensive measurements shower simulations. show results average standard deviation versus primary energy, analyze max}$-dataset at distribution level estimate ray composition. Our approach uses unbinned likelihood analysis, making use existing parametrizations max}$-distributions per element. has been repeated three main models hadronic interactions. Results are consistent a significant light-mass fraction, best fit $23$ $39$ $\%$ protons plus helium, depending choice interaction model. fraction intermediate-mass nuclei dominates. This confirms earlier LOFAR, systematic uncertainties now lowered 7 $9$ $\mathrm{g/cm^2}$. find agreement compared Pierre Auger Observatory, within statistical uncertainties. However, line results, we slightly lower max}$. values tension those found but agree other observatories Northern hemisphere.