Exploratory calculation of the rare hyperon decay $Σ^+ \to p \ell^+ \ell^-$ from lattice QCD
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2025
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| _version_ | 1866916683679006720 |
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| author | Erben, Felix Gülpers, Vera Hansen, Maxwell T. Hodgson, Raoul Portelli, Antonin |
| author_facet | Erben, Felix Gülpers, Vera Hansen, Maxwell T. Hodgson, Raoul Portelli, Antonin |
| contents | The rare hyperon decay $Σ^+ \to p \ell^+ \ell^-$ is a flavour-changing neutral current process mediated by an $s \to d$ transition that occurs only at loop level within the Standard Model. Consequently, this decay is highly suppressed, making it a promising avenue for probing potential new physics. While phenomenological calculations have made important progress in predicting the decay amplitude, there remains a four-fold ambiguity in the relevant transition form factors that prevents a unique prediction for the branching fraction and angular observables. Fully resolving this ambiguity requires a first-principles Standard-Model calculation, and the recent observation of this process using LHCb Run 2 data reinforces the timeliness of such a calculation. In this work, we present the first lattice-QCD calculation of this decay, performed using a 2+1-flavour domain-wall fermion ensemble with a pion mass of 340 MeV. At a small baryon source-sink separation, we observe the emergence of a signal in the relevant baryonic four-point functions. This allows us to determine the positive-parity form factors for the rare hyperon decays from first-principles, albeit with large statistical and systematic uncertainties. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2504_07727 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Exploratory calculation of the rare hyperon decay $Σ^+ \to p \ell^+ \ell^-$ from lattice QCD Erben, Felix Gülpers, Vera Hansen, Maxwell T. Hodgson, Raoul Portelli, Antonin High Energy Physics - Lattice High Energy Physics - Phenomenology The rare hyperon decay $Σ^+ \to p \ell^+ \ell^-$ is a flavour-changing neutral current process mediated by an $s \to d$ transition that occurs only at loop level within the Standard Model. Consequently, this decay is highly suppressed, making it a promising avenue for probing potential new physics. While phenomenological calculations have made important progress in predicting the decay amplitude, there remains a four-fold ambiguity in the relevant transition form factors that prevents a unique prediction for the branching fraction and angular observables. Fully resolving this ambiguity requires a first-principles Standard-Model calculation, and the recent observation of this process using LHCb Run 2 data reinforces the timeliness of such a calculation. In this work, we present the first lattice-QCD calculation of this decay, performed using a 2+1-flavour domain-wall fermion ensemble with a pion mass of 340 MeV. At a small baryon source-sink separation, we observe the emergence of a signal in the relevant baryonic four-point functions. This allows us to determine the positive-parity form factors for the rare hyperon decays from first-principles, albeit with large statistical and systematic uncertainties. |
| title | Exploratory calculation of the rare hyperon decay $Σ^+ \to p \ell^+ \ell^-$ from lattice QCD |
| topic | High Energy Physics - Lattice High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2504.07727 |