If the high-energy (TeV-PeV) neutrinos discovered by IceCube are made via proton-photon interactions in astrophysical sources, their energy spectrum may have a bump-like feature at a characteristic energy. We search for such a feature in present-day IceCube High-Energy Starting Events (HESE), on top of a power-law spectrum expected from alternative production via proton-proton interactions, and make forecasts using the expected exposure of upcoming neutrino telescopes.

We find no significant evidence of bumps in 7.5 years of HESE data, but a bump centered at ~1 PeV is only marginally disfavored. If the true flux does contain such a bump it could be discovered by 2027 using the combined exposure of IceCube, Baikal-GVD, and KM3NeT:

For more information, including interpreting limits on bumps as limits on the properties of the neutrino source population, see

Bump-hunting in the diffuse flux of high-energy cosmic neutrinos
Damiano F. G. Fiorillo, Mauricio Bustamante
arXiv:2301.00024

Fifty years ago, Berezinsky first predicted ultra-high-energy (UHE) neutrinos, the most energetic ones expected, about a thousand times more so than those seen by IceCube so far. Today, we have yet to discover them, but this may finally change in the near future!

IceCube-Gen2, and other upcoming neutrino telescopes, have a real chance of discovering the long-sought diffuse flux of UHE neutrinos. In a new paper, led by Víctor B. Valera and in collaboration with Christian Glaser, we make detailed, robust, and realistic discovery prospects:

Near-future discovery of the diffuse flux of ultra-high-energy cosmic neutrinos
Victor Branco Valera, Mauricio Bustamante, Christian Glaser
arXiv:2210.03756

Our results are promising: we find that if we are lucky this can happen within only a handful of years of operation! Figures 1 and 14 are the money plots.  Figure 1, reproduced below, shows that most flux models can be discovered within ten years of Gen2 and most within a handful of years. 

Figure 14, in the paper, shows that, in the event of flux discovery, most models can be distinguished from each other.

This paper is a companion to two earlier papers of ours that use the same computational framework that accounts for theory and experimental nuance to make forecasts:

• Measuring the UHE neutrino-nucleon cross section (also led by Victor Valera): https://arxiv.org/abs/2204.04237
• Discovering point sources of UHE neutrinos (led by postdoc Damiano Fiorillo): https://arxiv.org/abs/2205.15985

In the near future, we expect that next-generation neutrino telescopes will provide us with the sensitivity required to discover the first sources of UHE neutrino point sources (> 100 PeV). In a recent paper, led by postdoc Damiano Fiorillo, we provided detailed forecasts for what the radio array of IceCube-Gen2 could achieve by looking for neutrino multiplets:

Read more at:

Near-future discovery of point sources of ultra-high-energy neutrinos
Damiano F.G. Fiorillo, Mauricio Bustamante, Victor B. Valera
arXiv:2205.15985

Recently, we put out a paper, led by PhD student Victor Valera, where we present the first complete forecasts of how well the planned radio array of IceCube-Gen2 will be able to measure the UHE (> 100 PeV) neutrino-nucleon cross section. The results are encouraging!

Read more at:

The ultra-high-energy neutrino-nucleon cross section: measurement forecasts for an era of cosmic EeV-neutrino discovery
Victor Branco Valera, Mauricio Bustamante, Christian Glaser
arXiv:2204.04237

Join us in the 2022 edition of the NBIA PhD Summer School on Neutrinos: Here, There & Everywhere. This time it will be mainly an in-person event!

Our week-long online NBI Neutrino Summer School “Here, There & Everwhere” wrapped up today!

Find the slides for all talks and hands-on exercises on Indico.

The video recordings of all of the lectures and topical seminars are in our YouTube channel.

Thanks to our guest lecturers Joachim Kopp, Olga Mena, and Foeteini Oikonomou, to our topical seminar speakers from NBI Jason Koskinen, Tom Stuttard, Tyler Corbett, Oleg Ruchayskiy, Shashank Shalgar, and Rasmus Hansen, and to our eighteen student speakers from around the world.

Here is a link to the video of my survey talk in the 1st EuCAPT Symposium (slides here): High-energy and ultra-high-energy cosmic neutrinos

Scientific American wrote an article about the multiple ongoing projects planning to detect ultra-high-energy neutrinos via radio: Searching for the Universe’s Most Energetic Particles, Astronomers Turn on the Radio

(Yours truly makes an appearance.)

Thanks to Katrina Miller for the article!

Recently I gave an online introductory talk about neutrinos in the Thursday Morning Science seminar series of the University of L’Aquila. Here is the recording of that (sorry about the audio problems at the beginning!):

The Niels Bohr International Academy (NBIA) invites PhD students and advanced Master students to the International PhD Summer School on Neutrinos: Here, There & Everywhere. This one-week school aims to bring the participants up to date with the latest developments in neutrino physics, from theoretical issues to experimental results, including astrophysical and cosmological aspects.

Students will be given topical introductions, along with an overview of the current state of the field and the open questions that confront it. The invited lecturers are internationally renowned experts in their fields. The school participants will gain a broad understanding of current theoretical problems in neutrino physics, state-of-the-art neutrino experiments, and applications of neutrinos in cosmology and astrophysics.

School dates: July 5-9, 2021

Registration and information: https://www.nbia.dk/neutrino2021

Registration deadline: March 31, 2021 (please register early)

Format: We are presently planning an in-person meeting, but we want to keep everyone safe, so we may revisit the school format if it becomes necessary or advisable due to travel or health restrictions

Participation fee: None

Questions: Please contact the organizers, Markus Ahlers (markus.ahlers@nbi.ku.dk) and Mauricio Bustamante (mbustamante@nbi.ku.dk)