From July 7 to 11, 2025, we hosted 53 PhD, MSc, and BSc students from around the world. They received lectures on neutrino theory & phenomenology, neutrino astrophysics, and neutrino cosmology. All in all, we had 9 lectures, 5 topical seminars from NBI locals, and 24 student talks.
Here are a few photos (photo credit to co-organizer Markus Ahlers):
Like for the 2021, 2022, and 2023 schools, all the videos from the school are available on our YouTube channel.
In the hot, dense cores of core-collapse supernova, neutrinos could coalesce to make new, heavy particles, like Majoron-like bosons, with masses from tens of MeV to more than 100 MeV. After escaping the supernova, these Majorons would decay into energies comparable to the parent Majoron mass, far more energetic than the standard supernova neutrinos emitted from the neutrinosphere, and arriving at Earth later than them.
Thanks to large upcoming neutrino detectors, we might observe these high-energy neutrinos from the next galactic core-collapse supernova. Combining all available detection channels provides us with information on the energy, flavor, and arrival times of these neutrinos.
In a new paper, led by NBI PhD student Bernanda Telalovic, we have shown for the first time that we can combine this information use to clearly distinguish neutrinos from Majoron decay from the standard neutrinos of the next galactic supernova.
And, on top of that, we fold in the large uncertainty that exists in supernova physics by using two sophisticated supernova simulations (hot and cold) from the Garching group, obtained for two different assumptions for the mass of the proto-neutron star. However, our results do not hinge on us knowing what the real model, since we marginalize over it.
Should we detect no high-energy neutrinos, we will be able to place upper bounds on the Majoron coupling to neutrinos that are more than an order of magnitude stronger than the ones inferred from the observation of neutrinos from SN 1987A:
We show explicitly how the bounds are different depending on the flavor texture of the Majoron.
Conversely, should we detect high-energy neutrinos with late arrival times (tens of seconds post-bounce), we will be able to measure the mass and flavor-universal coupling of the Majoron:
Mauricio Bustamante 