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Reference : UMR6457-FREYER-001
Workplace : NANTES
Date of publication : Tuesday, May 04, 2021
Scientific Responsible name : Frederic Yermia
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Precision measurement of solar neutrino oscillation parameters with the JUNO small PMTs system and test of the unitarity of the PMNS matrix.
The study of the neutrino oscillation phenomenon allows the exploration of the leptonic flavor mixing within the framework of the Standard Model (SM) of particle physics. The phenomenology of these oscillations derives from the mixing of three flavors (e, mu, tau), described by the PMNS matrix (Pontecorvo-Maki-Nakagawa-Sakata), and from neutrinos relative masses. The SM does not predict the value of these parameters, which must therefore be measured. It started with the SuperKamiokande and SNO experiments, after they confirmed the existence of Neutrino oscillations (Nobel Prize in Physics in 2015). Today nearly all experimental results (despite the persistence of some anomalies) fit into this three-flavor paradigm. Oscillation parameters are known at the few percents level, even if the mass hierarchy (which is the lightest neutrino?) and the CP violation phase (is the mixing the same for neutrinos and anti-neutrinos) are yet to be determined. The JUNO experiment will allow to reach an unprecedented precision and to place the measurement of the so-called solar mixing parameters below one percent. These very high precision measurements will help to test the unitarity of the PMNS matrix . Any deviation could indicate the existence of new physics beyond the SM.
The Jiangmen Underground Neutrino Observatory (JUNO), under construction in China, is a multipurpose neutrino experiment aiming at the determination of the neutrino mass hierarchy from vacuum oscillation and at the precise measurement of solar and atmospheric oscillation parameters. To ensure a precise control of the systematic uncertainties of the detector, a double calorimetry system has been adopted. The interaction of neutrinos in the detector target (20 kilo-tons of liquid scintillator) is thus recorded by two complementary PMT systems, one composed of large, 20-inch PMTs (LPMTs) and the other one of small, 3-inch PMTs ( sPMTs). The first ensures a large optical coverage of the target and thus offers excellent energy resolution while the second provides photon counting and offers excellent temporal resolution. A new methodology called dual calorimetry is designed: comparisons between LPMT and SPMT systems allow the energy response to be kept linear within 1 % and the energy resolution to reach the 3% required at 1 MeV for mass ordering determination with JUNO.
The proposed thesis topic within the Subatech Neutrino group will focus on the precision measurement of solar oscillation parameters with the sPMTs system and the study of the main unitarity relation related to them . A work on the reconstruction with the sPMTs system and on the systematic errors thanks to the double calorimetry will also be an important contribution in order to meet the scientific objectives of a precision measurement with JUNO. The small but not negligible matter effects with JUNO will also have to be taken into account in this study. The different measurements of the mixing parameters will also provide an improved constraint on the first unitarity relation (|Ue1 |2 + |Ue2 |2 + |Ue3 |2 = 1) of the PMNS matrix . The PhD student should be able to complement her/his results with studies on the sensitivities of future measurements. The data collection being planned to start in 2022, after the first studies on GEANT4 simulations, the analyses will be carried out on the very first dataset acquired by the JUNO collaboration. For all these analyses, Machine Learning methods will be developed, to complement or surpass classical approaches.
The Neutrino group at Subatech has a recognized expertise in the field of neutrino physics. The group participates in short and medium range experiments at nuclear reactors (SoLid, Double Chooz, JUNO), in an experiment for the detection of astrophysical or atmospheric neutrinos (KM3Net) and also carries out research and development activities for future neutrino detectors (Liquido).
 Unitarity Tests of the Neutrino Mixing Matrix, Qian X. et al.. Preprint at arXiv:1308.5700
 Framework for testing leptonic unitarity by neutrino oscillation experiments - Fong, Chee Sheng et al. JHEP 1702 (2017) 114 arXiv:1609.08623 [hep-ph] YACHAY-PUB-16-02-PN
Subatech laboratory in Nantes in the Neutrinos team. It has a recognized expertise in the field of neutrino physics. The group participates in short and medium range experiments at nuclear reactors (SoLid, Double Chooz, JUNO), in an experiment for the detection of astrophysical or atmospheric neutrinos (KM3Net) and has research and development activities for future neutrino detectors (Liquido)
The candidate must hold a master's degree in particle, nuclear or astroparticle physics.
Required knowledge :
- general knowledge in particle and nuclear physics
- good knowledge in programming
- in-depth knowledge in experimental physics.
- Programming in C++ and with ROOT
- Use of the Geant4 transport code
- know how to work in a team on a large-scale project and internationally
- Ability to communicate and valorize work (presentation of work, participation in conferences, participation in the writing of articles, ...)
- fluency in English (written/spoken)
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