Postdoctoral Researcher in Neutrino Physics in Japan (M/F)

Job Description

Missions

The Hyper-Kamiokande experiment aims to achieve precision measurements of both the atmospheric oscillation parameters and the CP-violating phase, as well as to test the unitarity of the PMNS matrix. To achieve this goal, it is crucial to reduce the systematic uncertainty associated with the detector response below 1%, whereas the corresponding uncertainties in Super-Kamiokande exceed 3%.

The successful candidate will be responsible for developing the first Hyper-Kamiokande oscillation analysis based on a joint fit of accelerator and atmospheric neutrino data. They will build upon the current developments of this combined fitting framework, adapting it to the Hyper-Kamiokande event reconstruction and selection chain, and will ultimately use it to perform the experiment's first oscillation analysis.

To achieve this objective, the candidate will lead the development of the Hyper-Kamiokande analysis framework, including event reconstruction, event selection, and systematic uncertainty evaluation. They will first assess the performance limits of our reconstruction algorithms based on likelihood methods and deep learning techniques, in order to identify the most suitable approaches for each specific task. In parallel, they will develop the complete event reconstruction chain for Hyper-Kamiokande. They will then evaluate the robustness of this chain with respect to detector modeling uncertainties and physics interactions (such as secondary pion interactions) in order to quantify, for the first time, the expected systematic uncertainties on the oscillation parameters.

The second part of the project will focus on reducing the model dependence of our oscillation results. The candidate may develop control samples ("side bands") as well as implement Bayesian machine-learning models to minimize systematic uncertainties. They will progressively incorporate these developments into the joint atmospheric and accelerator neutrino fitting framework of Hyper-Kamiokande. In doing so, they will develop the official analysis framework that will underpin the first Hyper-Kamiokande oscillation analysis.

The candidate will initially use the framework they have developed to perform a comprehensive sensitivity study of Hyper-Kamiokande's oscillation measurements. They will then carry out the first Hyper-Kamiokande oscillation analysis themselves, with the goal of producing the experiment's first constraints on oscillation parameters in 2028. Should the availability of Hyper-Kamiokande data be delayed, the researcher will have access to Super-Kamiokande and T2K data to validate the analysis framework and, in the process, produce the most robust and sensitive oscillation analysis currently available in this field.

To accomplish these goals, the candidate will work closely with the teams at ILANCE, LLR, and IPMU. They will have the opportunity to supervise several students already heavily involved in these developments, covering machine learning, event reconstruction, and oscillation analyses. Depending on their interests, the postdoctoral researcher will also be encouraged to participate in phenomenological studies and analyses using neutrino oscillation fitting tools, including topics such as low-energy leptogenesis, PMNS unitarity, and leptonic flavor symmetry models, in collaboration with students and theorists already active in these research areas. The candidate will also have the unique opportunity to participate directly in the construction of the Hyper-Kamiokande detector on site in Kamioka.

Activity

* Development of the complete Hyper-Kamiokande event reconstruction and systematic uncertainty evaluation framework.
* Reduction of systematic uncertainties using machine learning techniques, control samples, and related methods.
* Validation of reconstruction and analysis algorithms using Super-Kamiokande calibration data as well as T2K accelerator and atmospheric neutrino data.
* Participation in Super-Kamiokande and/or T2K oscillation analyses.
* Analysis of the first Hyper-Kamiokande data.
* Participation in the construction of Hyper-Kamiokande.
* Presentation of results at collaboration meetings and international conferences.
* Publication of results in peer-reviewed scientific journals.

Your Profil

Skills

* PhD in experimental particle physics.
* Strong programming skills in Python, C++, and ROOT; knowledge of Fortran is desirable.
* Proficiency in written and spoken English (minimum B2 level).
* Strong communication skills and ability to work effectively within a collaborative team.

Given the ambitious nature of the project, the successful candidate is expected to possess a strong background in neutrino physics and event reconstruction. Significant experience in machine learning will be considered an asset. In addition, the candidate should demonstrate a high degree of scientific independence and be willing and able to supervise students in order to achieve the project's ambitious objectives.

Your Work Environment

**ILANCE Laboratory, CNRS-IN2P3 / The University of Tokyo**

ILANCE stands for *International Laboratory for Astrophysics, Neutrino and Cosmology Experiments*. It is a joint laboratory between the CNRS and the University of Tokyo, located on the Kashiwa Campus of the University of Tokyo. Its primary research areas include cosmology, dark matter, neutrino physics, and particle physics.

Over the coming decade, the major experiments planned in these fields have the potential to revolutionize our understanding of the formation and evolution of the Universe, with significant contributions from the ILANCE teams. This international laboratory provides an exceptional educational and research environment for French and Japanese PhD students, postdoctoral researchers, and visiting students.

Based in Japan, ILANCE brings together researchers, students, postdoctoral fellows, engineers, and technicians from the CNRS and Japanese institutions. The laboratory includes both international scientists undertaking long-term stays in Japan and Japanese physicists.

The neutrino group is led by Benjamin Quilain and Michel Gonin and focuses on neutrino oscillation experiments in Japan: T2K, Super-Kamiokande, and Hyper-Kamiokande. The group currently consists of two permanent researchers, two postdoctoral researchers, and five PhD students holding joint appointments between ILANCE and the Laboratoire Leprince-Ringuet (UMR 7638).

Within the context of this project, the group leader coordinates the Hyper-Kamiokande reconstruction effort and contributes to the T2K oscillation analysis working groups. The group also collaborates closely with the IPMU team (P. De Perio et al.) and software engineers at LLR to establish strong leadership in the development of machine-learning-based algorithms that are usable, robust, and thoroughly validated before the start of Hyper-Kamiokande operations.

Depending on the candidate's interests, up to six months per year may be spent in France working at the Laboratoire Leprince-Ringuet.

Travel to Kamioka and/or Kyoto is expected in order to finalize analyses and/or participate in detector construction activities and data-taking shifts.

Compensation and benefits

Compensation

Gross monthly salary between €2,991.58 and €4,756.76, depending on experience

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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