https://doi.org/10.1140/epjc/s10052-022-10146-x
Regular Article - Theoretical Physics
Revisiting 
decays
1
Dipartamento di Fisica e Astronomia “G. Galilei”, Università degli Studi di Padova, Padua, Italy
2
Istituto Nazionale Fisica Nucleare, Sezione di Padova, 35131, Padua, Italy
a
alfredowaltermario.guerrera@studenti.unipd.it
Received:
21
June
2021
Accepted:
21
February
2022
Published online:
2
March
2022
The theoretical calculation for pseudo-scalars hadronic decays 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 
decay and the present/future KOTO results for the 
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.
© The Author(s) 2022
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