The theoretical calculation for pseudo-scalars hadronic decays K→ πa is reviewed. While one-loop penguin contributions are usually considered, tree-level processes have most often been overlooked in literature. Following the Lepage–Brodsky approach the tree-level contribution to the charged and neutral pseudo-scalar decay in ALP is estimated. Assuming generic ALP couplings to SM fermions, the latest NA62/E949 results for the K+→ π+a decay and the present/future KOTO results for the KL0→π0a decay are used to provide updated bounds on the ALP-fermion Lagrangian sector. Finally, the interplay between the tree-level and one-loop contributions is investigated.
Revisiting K→ πa decays
Guerrera A. W. M.;Rigolin S.
2022
Abstract
The theoretical calculation for pseudo-scalars hadronic decays K→ πa is reviewed. While one-loop penguin contributions are usually considered, tree-level processes have most often been overlooked in literature. Following the Lepage–Brodsky approach the tree-level contribution to the charged and neutral pseudo-scalar decay in ALP is estimated. Assuming generic ALP couplings to SM fermions, the latest NA62/E949 results for the K+→ π+a decay and the present/future KOTO results for the KL0→π0a decay are used to provide updated bounds on the ALP-fermion Lagrangian sector. Finally, the interplay between the tree-level and one-loop contributions is investigated.
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