Probing long-lived axions at the KOTO experiment

Yoav Afik, Babette Döbrich, Jan Jerhot, Yotam Soreq, Kohsaku Tobioka

Research output: Contribution to journalArticlepeer-review


While the main goal of the J-PARC KOTO experiment is to measure the rare decay KL→π0νν¯, the unique setup of KOTO raises the possibility to search for physics beyond the Standard Model, in an attempt to probe parts of the parameter space which are not covered by other experiments. In this paper, we test the possibility of using KOTO to search for heavy QCD axions, or axionlike particles, a well-motivated extension of the Standard Model emerging in a variety of models. In particular, we estimate the sensitivity of the current KOTO setup as well as KOTO Step 2 for various benchmark scenarios of axion coupling to the Standard Model. We find that KOTO Step 2 can probe new regions in the parameter space, while KOTO with its current form can only reaffirm the existing bounds. The obtained axion datasets are available as an update of the public code of the alpinist framework, including implementation of KOTO setups in the simulation, allowing for interpretation of various analyses as searches for axions in custom models.

Original languageEnglish
Article number055007
JournalPhysical Review D
Issue number5
StatePublished - 1 Sep 2023

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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