Direct CP Violation in \(K \rightarrow \mu ^+ \mu ^-\)

  • T. KitaharaEmail author
Conference paper
Part of the Springer Proceedings in Physics book series (SPPHY, volume 234)


The upgrade of the LHCb experiment will probe a rare decay \(K_S \rightarrow \mu ^+ \mu ^-\) precisely. Although the process is dominated by CP-conserving decay, one can extract CP-violating pieces via the precise measurement. In this contribution, I introduce an interference contribution between \(K_L\) and \(K_S\) that is sensitive to a direct CP violation. It is found that the interference contribution can affect \(\text {Br}(K_S\rightarrow \mu ^+ \mu ^-\)) Standard Model prediction up to \(60\,\%\). It is also found that an unknown sign of an amplitude of \(K_L \rightarrow \gamma \gamma \) can be determined by measuring the interference effect, which can much reduce a theoretical uncertainty of \(\text {Br}(K_L \rightarrow \mu ^+ \mu ^-\)). I also show that the interference contributions in new physics models and their correlations with other kaon rare decays, especially \(\varepsilon ^{\prime }/\varepsilon \). This contribution is based on D’Ambrosio and Kitahara in Phys Rev Lett 119:201802, 2017, Chobanova et al. in JHEP 1805:024, 2018, Endo et al. in JHEP 1804:019, 2018.


Kaon rare decay Flavor changing neutral current Electroweak penguin CP violation 



I would like to thank Veronika Chobanova, Giancarlo D’Ambrosio Motoi Endo, Toru Goto, Miriam Lucio Martinez, Diego Martinez Santos, Satoshi Mishima, Isabel Suarez Fernandez, Daiki Ueda, and Kei Yamamoto for fruitful collaborations on the presented works. I also want to warmly thank the organizers of 16th Conference on Flavor Physics and CP Violation (FPCP 2018) for inviting and giving me the opportunity to present this result in a great conference.


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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Institute for Advanced ResearchNagoya UniversityNagoyaJapan
  2. 2.Kobayashi-Maskawa Institute for the Origin of Particles and the UniverseNagoya UniversityNagoyaJapan
  3. 3.Physics DepartmentTechnion–Israel Institute of TechnologyHaifaIsrael

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