Seminarium Fizyki Wielkich Energii

Strong interactions preserve an approximate isospin symmetry between up and down quarks. For K meson production, an exact isospin symmetry would lead to equal numbers of charged and neutral kaons produced in collisions of isospin-symmetric atomic nuclei. A recent NA61/SHINE measurement, published in Nature Communications, reports that in centralAr+Sc collisions at sqrt(s_NN) = 11.9 GeV the production of chargedkaons at mid-rapidity is (18.4 ± 6.1)% higher than that of the neutral kaons. Earlier nucleus-nucleus data spanning AGS to RHIC energies are consistent with this result, and the combined deviation from the isospin-symmetric expectation reaches 4.7 sigma. Known isospin-symmetry-breaking effects and the neutron excess of the colliding nuclei account for only a few-percent deviation in standard hadronic and transport calculations such as HRG or UrQMD, and cannot explain the observation. In this talk I will present the experimental result and briefly review some of the theoretical proposals discussed at the Iso-Break 2025 workshop. I will then introduce a data-driven framework based on minimal quark counting that extracts three dimensionless observables directly from charged pion, charged kaon and K0s multiplicities, separating constituent-quark memory from a possible vacuum flavour asymmetry.