Study of the $Λ\to p \ell \barν_\ell$ semileptonic decay in lattice QCD
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arXiv
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| Natura: | Preprint |
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2025
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| author | Bacchio, Simone Konstantinou, Andreas |
| author_facet | Bacchio, Simone Konstantinou, Andreas |
| contents | We present the first lattice QCD determination of the $Λ\to N$ vector and axial-vector form factors, which are essential inputs for studying the semileptonic decay $Λ\to p \ell \barν_\ell$. This channel provides a clean, theoretically controlled avenue for extracting the CKM matrix element $|V_{us}|$ from the baryon sector. Our analysis uses a gauge ensemble with physical light, strange, and charm quark masses and yields the most precise determination to date of the full set of transition form factors -- including second-class contributions -- as well as the associated couplings, radii, and the ratio of muon-to-electron decay rates, an observable sensitive to possible non-standard scalar and tensor interactions. We compare our non-perturbative results with next-to-next-to-leading order expansions in the small parameter $δ= (m_Λ- m_N)/m_Λ\approx 0.16$. We find that the common phenomenological approximation of neglecting the $q^2$-dependence of the form factors leads to a $\sim 4\%$ deviation in the decay rate. This underscores the critical importance of precise, fully non-perturbative form factor inputs for achieving the sub-percent precision targets of upcoming experimental programs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_09970 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Study of the $Λ\to p \ell \barν_\ell$ semileptonic decay in lattice QCD Bacchio, Simone Konstantinou, Andreas High Energy Physics - Lattice High Energy Physics - Phenomenology We present the first lattice QCD determination of the $Λ\to N$ vector and axial-vector form factors, which are essential inputs for studying the semileptonic decay $Λ\to p \ell \barν_\ell$. This channel provides a clean, theoretically controlled avenue for extracting the CKM matrix element $|V_{us}|$ from the baryon sector. Our analysis uses a gauge ensemble with physical light, strange, and charm quark masses and yields the most precise determination to date of the full set of transition form factors -- including second-class contributions -- as well as the associated couplings, radii, and the ratio of muon-to-electron decay rates, an observable sensitive to possible non-standard scalar and tensor interactions. We compare our non-perturbative results with next-to-next-to-leading order expansions in the small parameter $δ= (m_Λ- m_N)/m_Λ\approx 0.16$. We find that the common phenomenological approximation of neglecting the $q^2$-dependence of the form factors leads to a $\sim 4\%$ deviation in the decay rate. This underscores the critical importance of precise, fully non-perturbative form factor inputs for achieving the sub-percent precision targets of upcoming experimental programs. |
| title | Study of the $Λ\to p \ell \barν_\ell$ semileptonic decay in lattice QCD |
| topic | High Energy Physics - Lattice High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2507.09970 |