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: https://www.nbi.ku.dk/english/namely_names/2020/three-young-scientists-from-nbi-receive-villum-young-investigator-grants/

Using high-energy astrophysical neutrinos, with TeV-PeV energies, we have placed limits on secret neutrino-neutrino interactions for mediator masses in the 1-100 MeV range.

While propagating to Earth, high-energy astrophysical neutrinos may interact resonantly with the cosmic neutrino background.  This would introduce a gap in the energy spectrum of the high-energy neutrinos.  We looked for this gap in 6 years of publicly available IceCube High Energy Starting Events (HESE).

Bounds on secret neutrino interactions from high-energy astrophysical neutrinos
Mauricio Bustamante, Charlotte Amalie Rosenstroem, Shashank Shalgar, Irene Tamborra

This complements our earlier work (1912.09115), which used supernova neutrinos to place limits on secret interactions, both from neutrino interactions inside the supernova core and from the propagation of neutrinos to Earth (these are the regions labeled “Shashank et al.” in the plot above).

Our paper on new limits on new, secret, neutrino-neutrino interactions beyond the Standard Model from core-collapse supernovae is out:

Core-collapse supernovae stymie secret neutrino interactions (1912.09115)
Shashank Shalgar, Irene Tamborra, Mauricio Bustamante

We find limits on the mass and coupling of the new mediator through which the secret interactions occur.  For mediator masses between 10 MeV and 15 GeV, our limits are the strongest to date.  For mediator masses above 100 MeV, our limits are the first.

On occasion of the upcoming appearance of the GRAND white paper in Science China Physics, Mechanics & Astronomy, we wrote a press release for the EurekAlert! news service of the AAAS:

Giant neutrino telescope to open window to ultra-high-energy universe

Also, GRAND made the cover of the February 2020 issue of the journal:

The flavor composition of high-energy cosmic neutrinos has long been recognized as a rich probe of particle physics and astrophysics.  We are rapidly making progress in measuring the flavor composition with higher precision.

To take stock of the present situation and of things to come, I chose what I think are some of the most interesting flavor-related questions, and laid them out according to when we will answer them and how easy it will be to answer them.  (Of course, there is some subjectivity involved in where the questions are place.)

Fore more information about the status and future prospects of flavor composition, see my recent talk at PAHEN: Flavor in high-energy cosmic neutrinos: Interpretation and new challenges.

There is vast potential to test new physics with high-energy cosmic neutrinos, and the community has started doing it.  As a way to help guide our collective efforts, we came up with a classification scheme of new-physics models:

The scheme classifies models according to the stages of the neutrino lifetime at which they may act — at production, during propagation, at detection — and what observables they may affect — energy spectrum, arrival directions, flavor composition, arrival times.

(The list of models above is representative, not exhaustive.)

For more information see:

• ICRC 2019 proceedings: Fundamental physics with high-energy cosmic neutrinos today and in the future (1907.08690), Carlos A. Argüelles, Mauricio Bustamante, Ali Kheirandish, Sergio Palomares-Ruiz, Jordi Salvado, Aaron C. Vincent

• My ICRC 2019 slides (click here)

For a while now, I had been working on a lightweight code to compute neutrino oscillation probabilities for arbitrary oscillation scenarios.

NuOscProbExact uses the method developed by Ohlsson and Snellman to compute probabilities exactly without the need of diagonalizing the Hamiltonian.

NuOscProbExact is fully written in Python 3.7, open source, and publicly available at this GitHub repository: github.com/mbustama/NuOscProbExact .

In the repository you will also find documentation and examples; the code itself is distributed with example files ready to run.

 

 

For details, see the accompanying paper:

NuOscProbExact: a general-purpose code to compute exact two-flavor and three-flavor neutrino oscillation probabilities, Mauricio Bustamante, [arXiv:1904.12391]