Isospin kaon anomaly and its consequences
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| Format: | Preprint |
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2025
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| _version_ | 1866909815860625408 |
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| author | Giacosa, Francesco Rohrmoser, Martin |
| author_facet | Giacosa, Francesco Rohrmoser, Martin |
| contents | 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 $6.4σ$--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 $p/n \sim 1.2$ and the hyperon ratio $Σ^{+}/Σ^{-}\sim1.4$. Finally, we extend the approach to antiquarks in the initial state, useful for e.g. pion-nucleus scattering reactions. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_02113 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Isospin kaon anomaly and its consequences Giacosa, Francesco Rohrmoser, Martin Nuclear Theory High Energy Physics - Phenomenology Nuclear Experiment 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 $6.4σ$--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 $p/n \sim 1.2$ and the hyperon ratio $Σ^{+}/Σ^{-}\sim1.4$. Finally, we extend the approach to antiquarks in the initial state, useful for e.g. pion-nucleus scattering reactions. |
| title | Isospin kaon anomaly and its consequences |
| topic | Nuclear Theory High Energy Physics - Phenomenology Nuclear Experiment |
| url | https://arxiv.org/abs/2504.02113 |