TUM Master Thesis chosen as PRL Editor’s Choice

The ALICE Collaboration, including Emma Chizzali of Laura Fabbietti’s group at the TUM, have demonstrated for the first time that the strong interaction between a proton and φ meson is attractive. These results are not only fundamental to nuclear and particle physics but also important to the understanding of the properties and composition of neutron stars, the densest objects in our universe.

Emma Chizalli is a member of Laura Fabbietti’s group at TUM. Image: E. Chizalli

A technique called “Femtoscopy” is used to measure two-particle correlations to study the strong interaction among hadrons. The excellent particle identification capabilities of the ALICE experiment as well as the small-inter particle distance of proton-proton collisions at the Large Hadron Collider (LHC) enables the first-time measurement of the p-φ correlation function with sufficient precision. 

The so obtained genuine p-φ correlation function is compared to several model predictions. This allows to pin down a moderately attractive p-φ interaction with a small absorption cross-section in vacuum. A bound state is not supported by data. These results provide valuable input and constraints to theoretical models needed to correctly interpret the existing experimental data on the in-medium properties of the φ meson, related to the search for a partial restoration of chiral symmetry. Additionally, the coupling constant between φ mesons and nucleons is extracted, which can be related to the interaction among strangeness-containing particles predicted to emerge in the core region of neutron stars via fundamental symmetry relations.  


Publication:  Experimental Evidence for an Attractive p−ϕ Interaction


Prof. Dr. Laura Fabbietti
Professorin für Dichte und seltsame hadronische Materie
Technische Universität München
e-mail: laura.fabbietti(at)