Is there a violation of isospin symmetry in the Kaon sector in HIC?

by Prof. Marcus Bleicher (Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet)

Wednesday 20 May 2026, 15:00 → 16:00 Europe/Budapest

We address the current status of the isospin-symmetry breaking as shown in the ratio R_K = (K+ + K−)/(K0 + anti-K0)  discovered by NA61/SHINE in nucleus–nucleus collisions at the CERN SPS, its confirmation by other experiments and studies in e++e−. In addition, we discuss the theoretical status as well as we outline experimental and theoretical priorities. We propose that this violation of isospin symmetry maybe understood by introducing results from color-string fragmentation in e+e− to nuclear reactions. This novel input allows for a consistent description of the e+e− data, proton+proton data and finally nucleus-nucleus data at all investigated energies. We conclude that the observed isospin violation in nucleus-nucleus reactions is explained by asymmetric production of up- and down-quarks in the elementary color field fragmentation process. However, the reason for the symmetry breaking in e+e- remains unclear.