{"id":88651,"date":"2025-04-02T15:06:01","date_gmt":"2025-04-02T13:06:01","guid":{"rendered":"https:\/\/wfa.uwr.edu.pl\/?p=88651"},"modified":"2025-04-02T15:06:10","modified_gmt":"2025-04-02T13:06:10","slug":"evidence-of-isospin-symmetry-violation-in-high-energy-collisions-of-atomic-nuclei","status":"publish","type":"post","link":"https:\/\/wfa.uwr.edu.pl\/en\/2025\/04\/02\/evidence-of-isospin-symmetry-violation-in-high-energy-collisions-of-atomic-nuclei\/","title":{"rendered":"Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei"},"content":{"rendered":"

Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei<\/h2>\n\n\n

A paper titled Evidence of isospin-symmetry violation in high-energy collisions of atomic nuclei<\/em> was published in the prestigious journal Nature Communication (Nature Commun. 16<\/strong>, (2025) no.1, 2849). The authors are the NA61\/SHINE collaboration including a group of a few scientists from our Faculty.<\/h3>\n\n\n\n

The quarks (up, down, strange, charm, beauty and top, called flavours) interact via the strong interaction. Quarks are the constituents of baryons, like proton (uud, u = up and d = down quark), and mesons (composed of quark and antiquark). The effective masses of u and d quarks are very similar and very low compared to other quarks. It makes the strong interaction preserving approximate isospin-symmetry between particles containing u and d quarks. As an example of this symmetry, mass of neutron (udd) is larger than proton (uud) only by \u223c 0.1%.<\/p>\n\n\n\n

With full preservation of isospin symmetry, identical numbers of isospin-symmetric particles should be produced in collisions of isospin-symmetric atomic nuclei. This should especially apply to the production of kaons – mesons that, in addition to the strange quark (or antiquark), also contain an antiquark (or quark) u<\/em> or d<\/em> (K0<\/sup> = d\u00afs, K+<\/sup> = u\u00afs, K\u2212<\/sup> = u\u00afs, K\u00af0<\/sup> = d\u00afs<\/em>).<\/p>\n\n\n\n

\"figure\"
Comparison of the spectrum of neutral velocities (\u202fK<\/em>0<\/sup>s<\/sub>) with the averaged spectrum of charged mesons (K<\/em>\u207a i K<\/em>\u207b) in the 10% most central Ar+Sc collisions.<\/figcaption><\/figure>\n\n\n\n

Generation of electrically charged quarks K (i.e., K+<\/sup> i K\u2212<\/sup><\/em>) and electrically inert kaons K0<\/sup><\/em> and antikaons K\u00af0<\/sup><\/em> has been measured by the NA61\/SHINE collaboration in the interaction of argon and scandium nuclei at an energy of 11.9 GeV per nucleon pair in the center-of-mass system.<\/p>\n\n\n\n

We found that charged K mesons are emitted much more frequently \u2013 by (18.4 \u00b1 6.1)% \u2013 than neutral mesons K<\/em>. Previous measurements are consistent with this result, but were not significant in view of their insufficient measurement accuracy.<\/p>\n\n\n\n

The models of hadron production, which include all known isospinsymmetry breaking effects can explain only a fraction of the observed excess. New systematic, high precision measurements and theoretical efforts are still needed to establish the origin of the observed large isospin-symmetry breaking.<\/p>\n\n\n\n

The coauthors of this publications affiliated with the Faculty of Physics and Astronomy UWr are Z. Fodor, M. Kuchowicz, M. Lewicki, M. Naskret, R. Szukiewicz, L. Turko, O. Vitiuk i E. Zherebtsova.<\/p>\n\n\n

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