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Prospects for ${K_L \rightarrow \pi ^0\nu \bar{\nu }}$, $K_S\rightarrow \mu ^+\mu ^-$, $K_L\rightarrow \pi ^0 \ell ^+\ell ^-$ and $\varepsilon '/\varepsilon $ after the new ${K^+ \rightarrow \pi ^+\nu \bar{\nu }}$ result from NA62

Blanke, Monika 1,2; Buras, Andrzej J.; Lazzeroni, Cristina; Swallow, Joel C.
1 Institut für Theoretische Teilchenphysik (TTP), Karlsruher Institut für Technologie (KIT)
2 Institut für Astroteilchenphysik (IAP), Karlsruher Institut für Technologie (KIT)

Abstract:

The recently announced NA62 measurement of the K+->pi+nu nu & strns; branching ratio, based on 2016-2024 data, is fully consistent with its very accurate Standard Model (SM) prediction. While it is not excluded that the final result based on 2016-2026 data will deviate from the SM prediction, the question arises whether a similar fate awaits the KL ->pi 0 nu nu & strns; decay. This decay is currently being searched for by the KOTO experiment, with the present upper bound roughly two orders of magnitude above its very precise SM prediction. The proposed KOTO II experiment aims to provide the first discovery of the KL ->pi 0 nu nu & strns; decay and measure its branching ratio. Building on the findings of several previous papers we demonstrate that in the presence of suitably chosen large new complex phases and of a small amount of new right-handed s & strns;d couplings, in addition to the left-handed ones, the KL ->pi 0 nu nu & strns; branching ratio can still be enhanced by one order of magnitude with respect to the SM prediction while keeping both K+->pi+nu nu & strns; and epsilon K SM-like. Simultaneously the decays KS ->mu+mu- , studied by LHCb, and KL ->pi 0 & ell;+& ell;- , searched for by KOTO II, can be strongly enhanced and the anomaly in the ratio epsilon '/epsilon , as claimed by Dual QCD, removed. ... mehr


Verlagsausgabe §
DOI: 10.5445/IR/1000198171
Veröffentlicht am 20.10.2026
Originalveröffentlichung
DOI: 10.1140/epjc/s10052-026-16418-0
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Astroteilchenphysik (IAP)
Institut für Theoretische Teilchenphysik (TTP)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 10.2026
Sprache Englisch
Identifikator ISSN: 1434-6044, 1434-6052
KITopen-ID: 1000198171
Erschienen in The European Physical Journal C
Verlag Springer-Verlag
Band 86
Heft 10
Seiten 1166
Vorab online veröffentlicht am 13.10.2026
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