Right-handed neutral leptons can provide a mechanism to generate the Standard Model neutrino masses.
You can take a look at some of the presentations and talks given on the topic:
Café com Física Seminar,
University of Coimbra, Portugal, November 2020,
on "A First Search for Heavy Neutral Leptons with a Liquid-Argon Detector".
[PDF]
Manchester Bohr Seminar,
University of Manchester, UK, March 2020 (VIRTUAL),
on "A First Search for Heavy Neutral Leptons with a Liquid-Argon Detector".
[PDF]
PhDiscussion18,
University of Manchester, UK, November 2018,
on "Heavy Neutral Leptons with the MicroBooNE Detector".
[PDF]
Seminario di Fisica,
University of Palermo, Italy, October 2017,
on "Ricerca dei Decadimenti di Neutrini Sterili Pesanti nel Rivelatore MicroBooNE".
[PDF]