Journal Article

PUBDB-2025-01138

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Exploratory calculation of the rare hyperon decay $\Sigma^+ \to p \ell^+ \ell^-$ from lattice QCD

Erben, F.Extern* ; Gülpers, V. ; Hansen, M. T. ; Hodgson, R. R. (Corresponding author)DESY* ; Portelli, A.

2025
Springer Heidelberg

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Please use a persistent id in citations: doi:10.1007/JHEP07(2025)038  doi:10.3204/PUBDB-2025-01138

Report No.: CERN-TH-2025-055; DESY-25-057; arXiv:2504.07727

Abstract: The rare hyperon decay $\Sigma^+ \to p \ell^+ \ell^-$ 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 an anticipated new analysis of the 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 $340 \, \text{MeV}$. 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.

Note: 35 pages, 16 figures and 6 tables. Prepared for submission to JHEP

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Contributing Institute(s):

1. Zeuthen Particle PhysicsTheory (Z_ZPPT)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)
2. RAD TORCH - Rare decays of heavy mesons to resonant channels (101106913) (101106913)
3. NewPhysLat - Search for new physics through lattice simulations (757646) (757646)
4. EuroPLEx - European network for Particle physics, Lattice field theory and Extreme computing (813942) (813942)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2025

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Database coverage:
; ; ; ; ; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; DOAJ Seal ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 5 ; JCR ; National-Konsortium ; SCOAP3 sponsored Journal ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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Linked articles:

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Preprint Erben, F. ; Gülpers, V. ; Hansen, M. T. ; Hodgson, R. R. (Corresponding author)DESY* ; Portelli, A.
Exploratory calculation of the rare hyperon decay Σ$^{+}$ → pℓ$^{+}$ℓ$^{−}$ from lattice QCD
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