Lepto-Baryogenetic Diagnosis of New Physics Models

• Applicant: Professorin Dr. Milada Margarete Mühlleitner
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564216559

While the Standard Model (SM) has seen a great success story, there remain open questions that cannot be solved within the SM. Among the most prominent ones are those for the understanding of the tiny neutrino masses, of the baryon asymmetry of the universe and what is the true nature of Dark Matter (DM). Their solution requires physics beyond the SM. So far, there has been no direct sign of new physics and the discovered Higgs boson behaves very SM-like. This renders the search for new physics a particularly difficult task that requires the usage of all available information. To understand the extremely small neutrino masses, a class of models incorporates the so-called seesaw mechanism, which in its simplest form extends the SM by additional sterile heavy neutrinos. An appealing variant is provided by the inverse seesaw mechanism where the seesaw scale is moved closer to the electroweak scale through the introduction of an electroweak scalar singlet. A dynamical mechanism for the generation of the baryon asymmetry is given by electroweak baryogenesis provided the three Sakharov conditions are fulfilled. Leptogenesis is a special variant of baryogenesis where the asymmetry is first generated between leptons and antileptons through CP-violating decays of the additional heavy neutrinos, which is then transformed into a baryon asymmetry through baryon-number violating sphaleron processes. In this proposal, we will explore two promising mechanisms for the generation of the baryon asymmetry, leptogenesis and electroweak baryogenesis, in conjunction with collider and DM observables as well as neutrino data as diagnosis tools for the new Standard Model. We will provide and include in our analysis high-precision predictions for the relevant parameters and observables. We will connect this investigation to the implications on the allowed parameter space and for collider signatures. We will develop advanced new computer tools and/or extend existing ones for the computaton of leptogenesis and baryogenesis, for the computation of the DM observables (relic density, direct detection), and for efficient parameter scans in the multidimensional parameter spaces of the investigated models. The combined usage of complementary information from particle physics, astroparticle physics and cosmology will allow us to corner the new physics landscape from different angles. We will use the gained knowledge to pave the path to future insights in the true model underlying nature in a two-fold way: We will develop benchmark points and processes that test the deduced phenomenology at current and future collider, DM, neutrino and gravitational waves experiments. We will use our broad view on the possible new physics landscape to provide guidelines for model building giving answers to still open questions. The developed tools that will be made publicly available, will be of use for the whole high-energy physics community.

• DFG Programme: Research Grants
• International Connection: Vietnam
• Partner Organisation: National Foundation of Science and Technology Development of Vietnam (NAFOSTED)
• Cooperation Partner: Dr. Thi Nhung Dao