Missions

Decays of heavy-quark hadrons allow to perform indirect searches for effects beyond the Standard Model, by comparing the measured decay properties to their Standard Model predictions. Although our world is made of baryons, most such studies in heavy-flavour physics to date are performed with mesons, and our knowledge of heavy-quark baryon properties remains very limited.

Although the baryons that contain a charm quark and at least one strange quark have been studied for more than 40 years, there are still significant gaps in our knowledge of their properties and decays. Notably, the absolute branching fractions of the Xi_c baryon decays are known to a very limited precision, while for the Omega_c, only relative decay rates have been measured. This is a significant limitation for any searches for physics beyond the Standard Model involving charm-baryon decays, or beauty baryons decays into charm baryons.

The Belle II detector at KEK (Japan) is aimed at precision measurements of properties of beauty and charm hadrons, as well as tau leptons (https://inspirehep.net/literature/1692393). The Belle II collaboration consists of more than 1000 scientists and is taking data since 2019. The key feature of the Belle II detector is the nearly 4pi angular acceptance, which allows to perform the full reconstruction of the visible collision products and calculation of the missing energy. Combined with conservation laws in e+e-->ccbar process (baryon number, electric charge, quark flavours), this allows to fully reconstruct only one charm hadron and deduce the properties of the other one. This, together with the powerful algorithms for full event interpretation and B-tagging, opens several opportunities to improve our knowledge of the strange-charm-baryon decay rates. The techniques for inclusive reconstruction of charm baryons developed in https://inspirehep.net/literature/1275621 will be extended to strange-charm baryons and improved. This technique can then be extended to other measurements, such as semileptonic decays of charm baryons.

Activités

Data analysis, participation in Belle II data collection and detector operation, outreach and dissemination, student supervision.

Compétences

-PhD in experimental particle physics
- Excellent skills in data analysis and software (python, ROOT, C++), teamwork abilities and proficiency in English
- Experience in Belle II data analysis is appreciated but not mandatory

Contexte de travail

Located in the heart of the Parc National des Calanques, on the Luminy campus, the CPPM is a joint research laboratory of the CNRS and Aix-Marseille University, with around 180 researchers, engineers and PhD students. The laboratory studies subjects ranging from particle physics to astroparticle physics and cosmology, with a strong technological focus on electronics, mechanics, instrumentation and computing, enabling the design and construction of cutting-edge detection systems, often called upon to operate under extreme conditions: in the depths of the sea, in space or underground. Most of our research is carried out as part of leading international scientific collaborations, and our contributions are recognized worldwide. CPPM is committed to ethical research and promotes diversity and inclusion in the workplace, and provides administrative and logistical support to newcomers, particularly PhD students. (more details here: https://www.cppm.in2p3.fr/web/fr/index.html)

Contraintes et risques

The successful candidate will be based at the CPPM in Marseille (https://www.cppm.in2p3.fr). Short-term trips to KEK (Japan) are to be expected as part of the role.