Isospin kaon anomaly and its consequences

Le résumé fourni par la source

Abstract Isospin symmetry is well fulfilled in the QCD vacuum, as evidenced by small mass differences of isospin partners and suppressed isospin-violating decays. Recently, the NA61/SHINE collaboration reported an unexpectedly large isospin-violating charged-to-neutral kaon ratio in Ar-Sc heavy-ion collisions (HIC). Using a quark recombination approach, we introduce a function of kaon multiplicities that reduces to unity in the isospin-symmetric limit independently of the scattering energy and type of nuclei. Using this quantity, we show that nucleus–nucleus collisions violate isospin sizably (at the $$6.4\sigma $$ 6.4 σ –level), while proton-proton data on kaon multiplicities do not. We predict other isospin-violating enhancements in HIC, such as the proton-to-neutron ratio $$p/n \sim 1.2$$ p / n ∼ 1.2 and the hyperon ratio $$\Sigma ^{+}/\Sigma ^{-}\sim 1.4$$ Σ + / Σ - ∼ 1.4 . Finally, we extend the approach to antiquarks in the initial state, useful for e.g. pion–nucleus scattering reactions.

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