| Preprint | |
| Report number | arXiv:2503.05865 ; LAPTH-008/25 |
| Title | New bound on the vectorial axion-down-strange coupling from $K^+ \to π^+ ν\bar ν$ data |
| Author(s) | Guadagnoli, Diego (Annecy, LAPTH) ; Iohner, Axel (Annecy, LAPTH) ; Lazzeroni, Cristina (Birmingham U.) ; Martinez Santos, Diego (U. A Coruna) ; Swallow, Joel C. (CERN) ; Toni, Claudio (Annecy, LAPTH) |
| Imprint | 2025-03-07 |
| Number of pages | 17 |
| Note | 17 pages, 8 figures |
| Subject category | hep-ex ; Particle Physics - Experiment ; hep-ph ; Particle Physics - Phenomenology |
| Abstract | 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. |
| Other source | Inspire |
| Copyright/License | preprint: (License: arXiv nonexclusive-distrib 1.0) |
Record created 2026-03-10, last modified 2026-03-25
