Studying supernovae at KM3NeT with low- and high-energy neutrinos


Core-collapse supernovae, the collapse of heavy stars under their own weight, are key drivers of the evolution of galaxies associated with multiple unsolved questions: Why do so many of them lead to cataclysmic explosions? Under what conditions do they create black holes? And could supernovae produce cosmic rays, these ultra-high energy nuclei which are observed on Earth but whose origin is unknown? Answers to these key questions could be provided by neutrinos. These weakly-interacting particles can be emitted by a supernova both at low-energes inside the star’s core [1], and at high-energy from cosmic ray production at the star’s periphery [2,3]. If a supernova takes place in our galaxy, both neutrino types could be detected, which would represent a spectacular breakthrough in astrophysics. This double detection is one of the major goals of the KM3NeT experiment. KM3NeT is composed of two detectors, ORCA and ARCA, currently both under construction and taking data in the Mediterranean Sea. ARCA is geared up towards the detection of neutrinos associated with cosmic rays and is hence particularly suited to searching for high-energy supernova neutrinos. Furthermore, recent studies [1] have shown that both ORCA and ARCA would detect low-energy neutrinos if a core-collapse supernova occurs in the Milky Way. KM3NeT already features an automated system which searches for these low-energy neutrinos, which would allow informing telescopes before a supernova explosion becomes visible.

This goal of this Ph. D. proposal is twofold. First, the candidate will design a search strategy for high-energy supernova neutrinos at the KM3NeT experiment [4]. Second, the candidate will perform combined studies of the low- and high-energy neutrino signals predicted by current supernova models in order to shed light on the properties of the progenitor star and the origin of cosmic rays. The position will be based at APC and will be co-supervised by Dr. Sonia El Hedri and Pr. Antoine Kouchner. 

Searches for high-energy neutrinos from a wide variety of cosmic objects are currently being performed at KM3NeT. To design a search tailored to supernova neutrinos, the candidate will model the different possible neutrino emission rates and energy spectra based on existing studies [2,3], and exploit information about the supernova localization which would be provided either by low-energy neutrino measurements or by optical and infrared telescopes. In particular, the candidate will study the impact of the knowledge of the supernova location on KM3NeT’s performance. In parallel, the candidate will study existing theoretical models for both low- and high-energy supernova neutrino emission in order to design a combined study of the two signals. Indeed, major emitters of high-energy neutrinos could be magnetars, which are neutron stars with an extremely large magnetic field [3]. The APC group is currently collaborating with the Astrophysics Instrumentation and Modelisation (AIM) laboratory, at CEA-Saclay, which has been investigating the impact of a large star rotation speeds and high magnetic fields on low-energy neutrino emission using state-of-the-art supernova simulations. Using both low- and high-energy emission models, the candidate will investigate how the detection of neutrinos from a magnetar would allow constraning its rotation velocity and the intensity of its magnetic field, and determining whether this magnetic field plays a role in cosmic-ray acceleration.

The KM3NeT group at APC plays a leading role in the search for low-energy supernova neutrinos at KM3NeT. As part of the KM3NeT collaboration, the candidate will participate in collaboration meetings (travelling 3-4 times per year), and take part in the data processing, detector monitoring, and maintenance activities. Beyond our experimental work, our group also focuses on phenomenological studies, for which we have been collaborating with teams working on the DUNE and DarkSide-20k experiments at APC, and on supernova modelisation at AIM (CEA-Saclay). We will also collaborate with AIM and with the LIGO/VIRGO group at IJCLab to perform combined study of neutrino and gravitational wave signatures of core-collapse supernovae. This thesis would therefore be an excellent opportunity for the candidate to work on both modelling and data analysis, and to discover a wide range of experiments.

Some experience with Python programming (optionally also C++) and with data analysis would be highly appreciated. Whenever possible, we strongly encourage candidates to also join us in advance for a master's project on a similar topic.

[1]  KM3NeT Collaboration, “The KM3NeT potential for the next core-collapse supernova observation with neutrinos”,
[2] A. Kheirandish et al, “Detecting high-energy neutrino minibursts from local supernovae with multiple neutrino observatories”,
[3] K. Murase et al, “Probing the birth of fast-rotating magnetars through high-energy neutrinos”,
[4] KM3NeT Collaboration, Letter of Intent for KM3NeT Phase 2 J.Phys. G43(2016) no.8, 084001,
[5] M. Bugli et al, “Three-dimensional core-collapse supernovae with complex magnetic structures II: Rotational instabilities and multi-messenger signatures”,


Sonia El Hedri, Antoine Kouchner






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