Bayesian Extraction of the Light-Meson Spectrum:Application to the COMPASS 3$\pi$ Final-State Data

by Florian Kaspar (TUM E18)

Thursday 10 Jul 2025, 09:30 → 10:30 Europe/Berlin

E18/ENE Seminar Room 3268 (TUM PH)

Just like the excitation of atoms helped us understand electrodynamics and quantum mechanics, the spectrum of excited hadrons, so-called resonances, lets us learn about the nature of the strong interaction. Predicting hadron resonances from first principles is not an easy feat, but with the vast computational resources available nowadays, so-called lattice QCD simulations have been able to verify several experimental observations. At the same time, the experimental setups have improved as well and more and more data has been collected, uncovering details about these short-lived states in a never-before seen way. Experimental measurements and theoretical predictions improving alongside one other creates the perfect environment to gain a deeper understanding of resonant states. Obtaining information about hadrons from measurements is typically not a straight forward task but requires a sophisticated fitting procedure during which the resonances are extracted. The large amount of collected data leads to a situation in which statistical uncertainties are so small that the dominant source of uncertainties on the results are of systematic nature.

In this talk, I will demonstrate how these types of analyses can suffer from instabilities and systematic uncertainties connected to the fitting procedure and how they can be addressed by including the proper prior information into the modeling procedure. By making use of the NIFTy framework for numerical information field theory, a new approach for performing a partial-wave analysis has been developed. I will conclude with results obtained by using this new method to fit to the three-pion final-state data of the COMPASS experiment.