TY  - EJOUR
AU  - Erben, Felix
AU  - Gülpers, Vera
AU  - Hansen, Maxwell T.
AU  - Hodgson, Raoul Rustell
AU  - Portelli, Antonin
TI  - Exploratory calculation of the rare hyperon decay Σ<sup>+</sup> → pℓ<sup>+</sup>ℓ<sup>−</sup> from lattice QCD
IS  - arXiv:2504.07727
M1  - PUBDB-2025-04561
M1  - arXiv:2504.07727
M1  - CERN-TH-2025-055
M1  - DESY-25-057
PY  - 2025
N1  - 35 pages, 16 figures and 6 tables. Prepared for submission to JHEP
AB  - 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.
KW  - Hadronic Matrix Elements and Weak Decays (autogen)
KW  - Lattice QCD (autogen)
LB  - PUB:(DE-HGF)25
UR  - https://bib-pubdb1.desy.de/record/639475
ER  -