Isospin puzzle at CERN
A recent experimental result was reported in a Nature Communications article about unexpectedly large violation of the so-called isospin violation in ultrarelativistic nucleus-nucleus collisions. According to the experimental data by the NA61/SHINE experiment at the CERN SPS accelerator, the yield of charged kaons are unexpectedly larger than the yield of the neutral kaons, also retrospectively confirmed by the world data, indicating a larger then expected breaking of the isospin symmetry (up<->down quark or proton<->neutron exchange symmetry). Together with the world data, we see 4.7sigma deviation from the model predictions.
This is rather puzzling, as the discovery of isospin approximate symmetry was a cornerstone during the development of the theory of strong interactions, called quantum chromodynamics (QCD).
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The NA61/SHINE experiment intends to study this effect in a purer experimental setting, using charged pion beams on carbon target. For details we refer to the original article.
In the NA61/SHINE experiment, the HUN-REN Wigner RCP group is an active contributor (András László, Zoltán Fodor, Barnabás Pórfy, Richárd Nagy).
Besides that, the ELTE group is also an active Hungarian group (Máté Csanád, Yoshikazu Nagai)
https://doi.org/10.1038/s41467-025-57234-6
[https://arxiv.org/abs/2312.06572]
https://cerncourier.com/a/isospin-symmetry-broken-more-than-expected
