### The light limit of the neutrino

Neutrinos are the most light particles in the universe, but we don't know your mass. In the current state of the research, the only thing that we can hope to do is find upper and lower limits. And in the previous weeks we have some interesting news about the upper limit.
In april Physics Review Letters published a paper in which a team of researcher have compared constraints from physically motivated neutrino mass models (i.e., ones respecting oscillation experiments) to those from models using standard cosmological approximations. They founded an upper limit about $0.26 \, eV$, almost 2 million times lighter than an electron.
Loureiro, A., Cuceu, A., Abdalla, F. B., Moraes, B., Whiteway, L., McLeod, M., ... & Rollins, R. P. (2019). Upper Bound of Neutrino Masses from Combined Cosmological Observations and Particle Physics Experiments. Physical review letters, 123(8), 081301. doi:10.1103/PhysRevLett.123.081301 (arXiv
In the meanwhile, just ten days ago, the KATRIN's team (KATRIN, Karlsruhe Trtitium Neutrino experiment) announced the new experimental upper limit: $1.1 \, eV$.
Aker, M., Altenmüller, K., Arenz, M., Babutzka, M., Barrett, J., Bauer, S., ... & Besserer, U. (2019). An improved upper limit on the neutrino mass from a direct kinematic method by KATRIN. arXiv:1909.06048.
The research of neutrino mass becomes more and more interesting: if the study of theoretical models combined with astronomical data gives us an idea of the range to look for, experiments will say the last word.
The hunt to the neutrino is still open!