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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2503.05865 |
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| _version_ | 1866915833439059968 |
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| author | Guadagnoli, Diego Iohner, Axel Lazzeroni, Cristina Santos, Diego Martinez Swallow, Joel C. Toni, Claudio |
| author_facet | Guadagnoli, Diego Iohner, Axel Lazzeroni, Cristina Santos, Diego Martinez Swallow, Joel C. Toni, Claudio |
| contents | We reinterpret publicly available $K^+ \to π^+ ν\barν$ data collected by NA62 from 2016 to 2024 to constrain the fundamental vectorial coupling of the QCD axion to down and strange quarks. Using a fully reproducible likelihood analysis and a complete renormalization-group evolution of the axion couplings from the Peccei-Quinn (PQ) scale to the kaon scale, we translate the experimental limit into bounds on both the low-energy flavour-violating coupling and the fundamental UV parameters. In the generic regime where strong contributions dominate the decay amplitude, we obtain $|(F_V)_{sd}(μ_K)| > 1.6 \times 10^{12}\,\text{GeV}$. The coexistence of parametrically suppressed weak contributions implies a second, conceptually distinct constraint: the fact that weak-amplitude dominance arises from highly tuned UV coupling configurations, translates into a conservative general lower limit on the PQ scale, $f_a > 4.9 \times 10^4\,\text{GeV}$. These results provide the strongest accelerator-based constraints on axion-induced $d \leftrightarrow s$ transitions and establish a robust lower bound on $f_a$, complementary to astrophysical limits. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_05865 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | New bound on the vectorial axion-down-strange coupling from $K^+ \to π^+ ν\bar ν$ data Guadagnoli, Diego Iohner, Axel Lazzeroni, Cristina Santos, Diego Martinez Swallow, Joel C. Toni, Claudio High Energy Physics - Phenomenology High Energy Physics - Experiment We reinterpret publicly available $K^+ \to π^+ ν\barν$ data collected by NA62 from 2016 to 2024 to constrain the fundamental vectorial coupling of the QCD axion to down and strange quarks. Using a fully reproducible likelihood analysis and a complete renormalization-group evolution of the axion couplings from the Peccei-Quinn (PQ) scale to the kaon scale, we translate the experimental limit into bounds on both the low-energy flavour-violating coupling and the fundamental UV parameters. In the generic regime where strong contributions dominate the decay amplitude, we obtain $|(F_V)_{sd}(μ_K)| > 1.6 \times 10^{12}\,\text{GeV}$. The coexistence of parametrically suppressed weak contributions implies a second, conceptually distinct constraint: the fact that weak-amplitude dominance arises from highly tuned UV coupling configurations, translates into a conservative general lower limit on the PQ scale, $f_a > 4.9 \times 10^4\,\text{GeV}$. These results provide the strongest accelerator-based constraints on axion-induced $d \leftrightarrow s$ transitions and establish a robust lower bound on $f_a$, complementary to astrophysical limits. |
| title | New bound on the vectorial axion-down-strange coupling from $K^+ \to π^+ ν\bar ν$ data |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2503.05865 |