New measurements in leptonic kaon and pion decays: experimental and theoretical perspectives

@misc{allwicher2026measurements,
  title = {{New measurements in leptonic kaon and pion decays: experimental and theoretical perspectives}},
  author = {Lukas Allwicher and Stefan Alexandru Ghinescu and Federico Mescia and Tommaso Spadaro and Lucine Tabatt},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2609.05231},
  eprint = {2609.05231},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.05231},
}

TY  - UNPB
TI  - New measurements in leptonic kaon and pion decays: experimental and theoretical perspectives
AU  - Lukas Allwicher
AU  - Stefan Alexandru Ghinescu
AU  - Federico Mescia
AU  - Tommaso Spadaro
AU  - Lucine Tabatt
PY  - 2026
DA  - 2026/10/05
PB  - arXiv
DO  - 10.48550/arxiv.2609.05231
UR  - https://arxiv.org/abs/2609.05231
AB  - We study the future prospects for precision measurements of purely leptonic charged-current kaon and pion decays. Together with the ratio of leptonic widths R_K^ν=Γ(K→ eν)/Γ(K→μν), we consider the single ratios R_Kπ^ℓ=μ,e = Γ(K → ℓν) / Γ(π→ ℓν), for which many experimental uncertainties cancel, as well as the double ratio R_Kπ^e / R_Kπ^μ, which provides a particularly sensitive probe of new physics. This study is timely in light of two converging developments. On the experimental side, a new conceptual design for a dedicated setup based on a slow-extracted proton beam and a multi-year data-taking program, is expected to achieve a precision at the few 10^−4 level. On the theory side, recent lattice-QCD calculations have reached a comparable level of accuracy. Finally, we assess the impact of these next-generation measurements on searches for physics beyond the Standard Model and show that they can provide constraints that are either competitive with or complementary to existing bounds.
ER  -