The Future of High-Energy Astrophysical Neutrino Flavor Measurements


There is a vast potential in using the measurement of the flavor composition of high-energy (TeV-PeV) astrophysical neutrinos to test astrophysics and fundamental physics. But there is also plenty of uncertainty in the prediction of the allowed flavor composition at Earth, due to the uncertainties in the mixing parameters, and in the measurement of flavor composition in neutrino telescopes. In other words, flavor is a powerful tool, but it needs sharpening.

In our latest paper, we show that in the next 20 years, flavor will become the sharp tool it was always meant to be, thanks to new oscillation experiments and new neutrino telescopes:

The Future of High-Energy Astrophysical Neutrino Flavor Measurements
Ningqiang Song, Shirley Weishi Li, Carlos A. Argüelles, Mauricio Bustamante, Aaron C. Vincent

By 2040, we will be able to use flavor composition by itself to identify the production mechanism of high-energy astrophysical neutrinos:

Regions of allowed flavor composition at Earth: 2020 vs. 2040

POEMMA paper


The big POEMMA paper is finally out! It contains the science case, goals, and design of POEMMA, a twin-satellite experiment to detect the fluorescence and Cherenkov emission from extensive air showers triggered by ultra-high-energy cosmic rays and neutrinos in the atmosphere.

The POEMMA (Probe of Extreme Multi-Messenger Astrophysics) Observatory
A.V. Olinto et al.

My own small contribution was mainly on the opportunities for beyond-the-Standard-Model neutrino opportunities at ultra-high energies.

Flavor boundaries with high-energy active-sterile neutrino mixing


If the three active neutrinos mix with a sterile one, i.e., in 3+1 scenarios, they may modify the flavor composition of high-energy astrophysical neutrinos. We analytically derived boundaries in flavor space to avoid having to sample over unknown mixing and help boost searches for new physics (we provided them in nice downloadable data tables, too):

Flavors of Astrophysical Neutrinos with Active-Sterile Mixing
Markus Ahlers, Mauricio Bustamante, Niels Gustav Nortvig Willesen

The solid lines are the new 3+1 boundaries, computed for the three benchmark production scenarios (three different colors), compared to the boundaries that we computed for three-flavor mixing (dashed lines) in our earlier paper (1810.00893):

Neutrinos as cosmic magnetometers


Where are the IceCube high-energy astrophysical neutrinos coming from? We don’t know yet! But if the neutrino sources harbor large magnetic fields, then maybe they will leave imprints (due to synchrotron radiation) on the neutrino flux. We looked for these imprints in public IceCube data:

Using High-Energy Neutrinos As Cosmic Magnetometers
Mauricio Bustamante & Irene Tamborra

We exclude large magnetic fields of 10 kG–10 MG:

Snowmass 2021 letters of interest


The deadline for submission of letters of interest (LoIs) for the US Snowmass 2021 process was Monday, August 31. There were ~1600 LoIs submitted and all of them can be found here: .

I was personally involved in or led a few:

  • Cosmic Neutrino Probes of Fundamental Physics [pdf]
  • Neutrino cross-sections and interaction physics [pdf] (with Amy Connolly & Spencer Klein)
  • New physics with astrophysical neutrino flavor [pdf] (with Carlos Argüelles, Teppei Katori, Ali Kheirandish, Sergio Palomares-Ruiz, Jordi Salvadó, Aaron Vincent)
  • Ultra-High-Energy Neutrinos [pdf] (with Peter Denton & Stephanie Wissel)
  • Target of Opportunity Observations with Next-Generation High-energy Neutrino Observatories [pdf] (with Claire Guépin & Tonia Venters)
  • An Andean Deep-Valley Detector for High-Energy Tau Neutrinos [pdf] (with Carlos Argüelles & Andrés Romero-Wolf)
  • GRAND: Giant Radio Array for Neutrino Detection [pdf]

Here is a plot I prepared, with feedback from many others, for Cosmic Probes of Fundamental Physics:

New limits on neutrino decay from the Glashow resonance


In a new paper, I place new limits on the lifetime of the nu_1 and nu_2 neutrinos, assuming they decay into a visible nu_3, in the inverted neutrino mass ordering:

New limits on neutrino decay from the Glashow resonance of high-energy cosmic neutrinos
Mauricio Bustamante
arXiv: 2004.06844

To place my new limts, I put to practice a proposal that we published earlier (1610.02096), that uses the observation of the Glashow resonance in IceCube, at a few PeV, as evidence of the survival of nu_1 and nu_2.

I base our present-day results on the observation of the first Glashow resonance candidate by IceCube.  For nu_2, the limit on the lifetime is the best one to date.  For nu_1, it is comparable to the best one to date, coming from solar neutrinos.  The limits quickly improve with just a handful more of Glashow resonances observed.


Call for PhD position on high-energy cosmic neutrino physics


I am currently looking to hire one PhD student to work with me on high-energy cosmic neutrino physics at the Niels Bohr Institute starting in Fall of 2020.

This is a 3-year position, fully funded by the Villum Fonden program “Pushing neutrino physics to the cosmic frontier.”

Find more details on INSPIRE: .

Application deadline: April 15, 2020

Contact me if you have any questions.

Interview in El Comercio newspaper


Recently I was interviewed by El Comercio, the largest national newspaper in Perú, about neutrinos, particles physics, and my Villum Young Investigator grant.  The interview appeared online and in print form on February 22, 2020.  Here is a link to the online version (in Spanish):

Peruano recibe US$15 millones para estudiar los vacíos de la física de partículas

Weirdly, the interview made it to the front page of the print version of newspaper:



Villum Fonden Young Investigator Award


I was recently awarded a Villum Fonden Young Investigator Award (in the amount of ~10M DKK ~= 1.3M euro) to carry out the project “Pushing Neutrino Physics to the Cosmic Frontier”.

This starting grant will allow me to form my own research group at the Niels Bohr Institute, and to fund it for the coming five years. Come Fall 2020, I will become Assistant Professor at the NBI.

More information: