Madagascar students take on tau neutrinos

Herilala Razafinime

Two students from the University of Antananarivo-Madagascar, the first African institution to join the DUNE collaboration, are producing their master’s theses on tau neutrino studies for DUNE. Herilala Razafinime and Miriama Rajaoalisoa spent the summer of 2017 at Fermilab as recipients of the laboratory’s Neutrino Physics Center (NPC) fellowship program.

This fellowship program brings members of the international neutrino community, experimentalists working on Fermilab experiments as well as neutrino theorists, to Fermilab for short- to medium-term visits.

Herilala Razafinime

“We had a presentation about the DUNE experiment and our university’s involvement in it,” said Razafinime. “It was really interesting and I decided to join.”

Razafinime’s work focused on analyzing charged current (CC) interactions of neutrinos in liquid argon to determine the number of tau neutrinos the DUNE Far Detector might be able to see. He focused on events where a tau lepton decays into an electron plus neutrinos, requiring the separation of such events from CC electron neutrino interactions and the additional background from neutral currents. He has used simulations from GENIE and classifiers from the ROOT TMVA (Toolkit for Multivariate Data Analysis) to identify a set of variables, before any detector reconstruction effects, to isolate the tau neutrinos from this background.

Razafinime analyzed two different beam configurations, one optimized for the study of CP violation and one optimized for tau neutrino appearance. His work indicates that a beam optimized for tau neutrino appearance in fact offers better sensitivity to tau neutrino measurement than the CPV-optimized beam by about an order of magnitude.

Miriama Rajaoalisoa

Miriama Rajaoalisoa

Rajaoalisoa attended the African School of Physics in 2016, a summer school devoted to the promotion of fundamental physics and its applications in Africa.

“It was during that school that I met Dr. Mary Bishai (of BNL). I was very impressed by her work and the DUNE experiment and I expressed to her my interest in joining,” she said. She and Razafinime began working remotely with Bishai that September, coached by David Martinez of IIT on the software tools.

Rajaoalisoa also studied tau neutrino appearance, but her work focused more on the actual reconstruction of tau neutrino CC events within the detector.  Utilizing the variables identified by Razafinime’s work, she was able to identify necessary improvements to the software to adequately reconstruct the hadronic system in neutrino interactions. She also explored for the first time the use of Convolutional Visual Networks (CVN) for the identification of tau neutrino CC interactions.

Igniting interest in tau neutrino physics

“Herilala and Miriama started looking at the very interesting and challenging possibility of detecting tau neutrino events in DUNE,” said Fermilab scientist Alberto Marchionni, who helped mentor the students.  “More work is certainly needed, but they have ignited some interest in this topic within the DUNE collaboration.”

Both students hope to pursue a Ph.D, working on the DUNE experiment.

“It’s impressive that these students started looking at this analysis – it is very hard,” said Marchionni. “Their participation is evidence that significant resources exist in the collaboration, and that the sensitivity and granularity expected from the DUNE Far Detector are stimulating new ideas.”


University of Antananarivo-Madagascar collaborators Laza Rakotondravohitra and Roland Raboanary, the students’ advisors, wish to acknowledge the supervision and mentorship provided to the two students throughout their work from Mary Bishai, David Martinez, Alberto Marchionni, and Fermilab’s Tingjun Yang.