Clearing the path to New Physics in charm with a novel hadronic-description toolkit

• Applicant: Eleftheria Solomonidi, Ph.D.
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 557031287

The study of the weak and strong interactions between quarks, especially in phenomena involving Standard-Model (SM) suppressed mechanisms like flavour-changing neutral currents, is commonly known as flavour physics and it plays an integral role in the indirect searches for New Physics (NP). While the weak decays of bottom and strange quarks are currently investigated at a very advanced level, the physics of the charm quark has so far received less attention. The recent first-time discovery of CP violation in the hadronic two-body decays of charm mesons marks a new era for the field, especially given that initial theoretical calculations indicate SM values significantly lower than the measured ones. This urges theorists to further look into the dynamics of the charm quark, putting an emphasis in the less controlled hadronic effects involved. In our project, we will act in two directions: first we will further refine the calculations involved in the theoretical determination of the observables related to the CP asymmetries in the decays of charmed mesons to two pions or two kaons. We plan to do so by extending the use of the method of Light-Cone Sum Rules (LCSRs) to calculate the decay amplitudes as well as the suppressed terms that enter the CP asymmetries, with a better precision. This will allow a direct confrontation of the theory with the experimental measurements and will help conclude on the nature of the latter. Secondly, we plan to provide SM predictions for a series of different phenomena involving a hadronic component. Specifically, we will study two- and three-body hadronic decays of charmed mesons and the mixing between neutral charmed mesons. For our calculations we will combine the implementation of LCSRs as well as data-driven, Omnes-type dispersion relations. Where applicable we will consider the use of the heavy-quark expansion. The comparison of a set of those observables to the experimental data will serve as a test of the theoretical methods used for the determination of non-perturbative QCD effects in the charm sector. When the different methods are compared and the validity of our approach is confirmed, the remaining observables will then provide the ground for disentangling SM from NP manifested in the phenomena under consideration.

• DFG Programme: WBP Position