Köln 2025 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 9: Heavy-Ion Collisions and QCD Phases II

HK 9.1: Talk

Monday, March 10, 2025, 16:45–17:00, HS 3 Chemie

Accessing the p–Σ⁺ interaction via femtoscopy with ALICE — •Benedict Heybeck for the ALICE Germany collaboration — Institut für Kernphysik, Johann Wolfgang Goethe-Universität Frankfurt, Frankfurt, Germany

The Σ–nucleon strong interaction is an important ingredient to understand the composition of neutron stars and is also crucial for theoretical predictions on potential Σ-hypernuclei. Data on this interaction is scarce and purely based on scattering experiments. Since data points are only available at rather high relative momenta and their uncertainties are sizeable, theory calculations are not well constrained. Particularly the triplet channel is very uncertain and it is not yet clear if the interaction in this channel is attractive or repulsive. In this regard, two-particle intensity interferometry (femtoscopy) of Σ baryons and nucleons can provide valuable information. Σ⁺ baryons decay into a proton and a neutral pion via the weak interaction with a branching ratio of 52%. The neutral pion decays electromagnetically almost exclusively into two photons which are challenging to measure with the ALICE apparatus. In this talk, a novel reconstruction method will be shown, which makes use of sophisticated reconstruction algorithms and machine learning techniques to improve the reconstruction efficiency and purity of the Σ⁺ baryons and allow for the measurement of their correlation function with protons for the first time. The obtained correlation function will be discussed and related to latest theoretical calculations, providing new constraints on the Σ–nucleon interaction.

Keywords: Femtoscopy; Strangeness; Machine Learning