Research

My research area is particle physics, and more precisely the theoretical interpretation of experimental data from accelerators. I use these data to study the physics of flavours, which concerns the six different types (or flavours) of quarks that make up matter, their interactions and their decays.

The theoretical description of the transitions from one flavour of quark to another is difficult because it involves different types of fundamental interactions, in increasing energy scales:

• At a few GeV, the strong interaction unites quarks into experimentally observed bound states, the hadrons. The transition from the language of quarks to that of hadrons requires an understanding of the effects of the strong interaction at low energies, which remain difficult to master theoretically because of their non-perturbative character.
• At about 100 GeV, the electroweak interaction is responsible for the decay of heavy quarks into light quarks (and leptons). It has a perturbative formulation that can be directly exploited in the framework of the Standard Model, in direct relation to an important theoretical question, the breaking of electroweak symmetry.
• At a higher scale, yet to be determined, interactions or particles beyond the Standard Model may also affect transitions from one quark flavour to another. Indeed, during a transition from one flavour to another, quantum mechanics allows these interactions or particles to appear in virtual intermediate states and to generate deviations from the Standard Model predictions.

Flavour physics thus has both the capacity to test the Standard Model (nonperturbative aspects of the strong interaction, electroweak symmetry breaking) and to propose extensions of the Standard Model at higher energies (deviations between observations and Standard Model predictions). I investigate these questions in both the heavy and light quark domains, using effective field theory tools in combination with other computational techniques of flavor physics.

My activities are naturally part of an international context, linked to current experimental research in flavour physics, in particular at CERN (LHCb, CMS, ATLAS, NA48 and NA62), in Japan (Belle II) and in China (BESIII), as well as to past experiments like Babar, Belle and CLEO-c. I am therefore also in regular discussion with different experimental groups.

Three main themes can be identified in my research activities:

• the study of the strong interaction at low energy, in order to understand the mechanism of chiral symmetry breaking and its consequences for light hadrons

• the analysis of the dynamics of heavy quarks and CP symmetry violation (particle vs. antiparticle) to determine the parameters of the Cabibbo-Kobayashi-Maskawa matrix

• the study of rare b-quark processes to investigate the possible contribution of physics beyond the Standard Model.