Erlangen 2026 – scientific programme

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T: Fachverband Teilchenphysik

T 10: Axions/ALPS I

T 10.1: Talk

Monday, March 16, 2026, 16:15–16:30, KH 01.013

Search for the K⁺ → π⁺ π⁰ X decay — •Marco Ceoletta — JGU Mainz (DE) + CERN (CH)

This analysis aims to search for the hypothetical decay channel K⁺ → π⁺ π⁰ X, where X is invisible and can be interpreted as an Axion-like particle (ALP, indicated as A) or as a massless Dark Photon (a), at the NA62 experiment (CERN). Obtaining a stringent upper limit on BR(K⁺ → π⁺ π⁰ X) is important for constraints on several BSM theories. In particular, for X=A the decay is sensitive to an axial-vector coupling of pseudo-scalar particles to quarks. A search on K⁺ → π⁺ π⁰ A therefore complements the extensive work already performed on the associated two-body decay K⁺ → π⁺ A, that is sensitive only to the polar-vector coupling current. A preliminary upper limit of the branching ratio to ALPs, as part of a feasibility study done in 2022, already outperformed the best previous limit using less than 20% of the available data. The presentation describes the analysis, the selection, and the background estimation and and gives an outlook on the expected upper limits.

Keywords: ALP; NA62; dark photon; rare decay searches