Neutrino telescopes instrument large volumes of water or ice with photomultipliers (PMTs) to detect the Cherenkov radiation emitted by charged leptons (mainly muons, but also electron- or tau-induced showers) induced neutrino that interact with the target transparent medium, inside or near the instru-mented volume. Since the Earth acts as a shield against all particles but neutrinos, their design is opti-mized for the detection of up-going particles produced by neutrinos which have traversed the Earth be-fore interacting in the vicinity of the detector.
Depending on their size and of the density of the PMT configuration, such detectors can be used for different physics purposes:
- km3-scale (or Gigaton-scale) detectors focus on the detection of high-energy (TeV--PeV) cosmic neutri-nos originating from astrophysical sources. The recent observation of an excess in the diffuse high-energy flux by the IceCube experiment has opened new perspectives for neutrino astronomy, calling for an increase in the detection efforts also in the Northern Hemisphere, in particular to increase the cover-age of the Galactic region;
- megaton-scale, denser detectors can address the fundamental properties of neutrinos, and in particu-lar their mass ordering needed to constrain the models that seek to explain the origin of mass in the lep-tonic sector and the differences within the mass spectrum of all elementary particles. They focus on lower energy (~GeV) neutrinos produced in the atmosphere.
Within this double perspective, the European KM3NeT project is deploying the next-generation neu-trino telescope in the Mediterranean Sea, with one site dedicated to TeV-PeV neutrino astronomy in Italy (ARCA), and one site dedicated to the measurement of the neutrino mass hierarchy in France (ORCA). KM3NeT builds on the expertise gained in the operation of the smaller detector ANTARES, de-ployed at a depth of ~2500m, off Toulon and currently the most sensitive detector in the Northern Hem-isphere. A major technological upgrade of KM3NeT consists in the use of novel multi-PMTs optical modules whose first prototypes are now successfully tested undersea. The construction of the detector on both sites has already started and is expected to extend during the period of this Ph.D.
The APC group is strongly involved in both KM3NeT/ARCA and KM3NeT/ORCA. The applicant will al-so take part in the deployment and exploitation of the first detection units. This involves the measure of the rates of various physical processes such as the coincidences induced by 40K decays and the recon-structed rate of down-going atmospheric muons, but also the search for the first neutrinos and the pub-lication of the first physics studies. The applicant will participate to the software development and to the tuning of the Monte Carlo parameters in order to reproduce the experimental results and validate the simulation. A contribution to the development of the Calibration Units (responsibility of APC within KM3NeT) is also envisaged. The Calibration Units are meant for the monitoring of the detector behavior in terms of collection efficiency, time and energy resolution, etc. Specific tools will also be installed for the long-term monitoring of environmental parameters, thus offering a bridge with Earth and Sea Sci-ences (possibly via the Labex UnivEarthS, of which APC is member)
The applicant’s research activities will be carried out in tight link with other French and European research groups participating to the project. Through his/her work, the applicant will become familiar with the state-of-the-art questions in (cosmic) neutrino physics, while acquiring some experience in pro-gramming (C++, ROOT, databases…) and in the statistical methods necessary to his/her project. The technical aspects of the project will also provide him/her with a first insight into detector devices (in particular photomultipliers) widely used in contemporary (astro-)particle physics.