Looking forward to test the KOTO anomaly with FASER

The search for light and long-lived particles at the LHC will be intensified in the upcoming years with a prominent role of the new FASER experiment. In this study, we discuss how FASER could independently probe such scenarios relevant for new physics searches at kaon factories. We put an emphasis on the proposed explanations for the recently observed three anomalous events in the KOTO experiment. The baseline of FASER precisely corresponds to the proposed lifetime solution to the anomaly that avoids the NA62 bounds on charged kaons. As a result, the experiment can start constraining relevant models within the first few weeks of its operation. In some cases, it can confirm a possible discovery with up to 104 spectacular high-energy events in FASER during LHC run 3. Further complementarities between FASER and kaon factories, which employ FASER capability to study γγ signatures, are illustrated for the model with axionlike particles dominantly coupled to $SU(2)_W$ gauge bosons.