%0 Electronic Article
%A Erben, Felix
%A Gülpers, Vera
%A Hansen, Maxwell T.
%A Hodgson, Raoul Rustell
%A Portelli, Antonin
%T Exploratory calculation of the rare hyperon decay Σ<sup>+</sup> → pℓ<sup>+</sup>ℓ<sup>−</sup> from lattice QCD
%N arXiv:2504.07727
%M PUBDB-2025-04561
%M arXiv:2504.07727
%M CERN-TH-2025-055
%M DESY-25-057
%D 2025
%Z 35 pages, 16 figures and 6 tables. Prepared for submission to JHEP
%X The rare hyperon decay Σ<sup>+</sup> → pℓ<sup>+</sup>ℓ<sup>−</sup> is a flavour-changing neutral current process mediated by an s → 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.
%K Hadronic Matrix Elements and Weak Decays (autogen)
%K Lattice QCD (autogen)
%F PUB:(DE-HGF)25
%9 Preprint
%U https://bib-pubdb1.desy.de/record/639475