(Formula Presented) and ε′/ε in simplified new physics models

Andrzej J. Buras, Dario Buttazzo, Robert Knegjens

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

Abstract: The decays K+→π+νν¯ and KL→π0νν¯, being the theoretically cleanest rare decays of mesons, are very sensitive probes of New Physics (NP). In view of the excellent prospects of reaching the Standard Model (SM) sensitivity for K+→π+νν¯ by the NA62 experiment at CERN and for KL→π0νν¯ by the KOTO experiment at J-PARC, we study them in the simplest extensions of the SM in which stringent correlations between these two decays and other flavour observables are present. We first consider simple models with tree-level Z and Z′ contributions in which either Minimal Flavour Violation (MFV) or a U(2)3 symmetry is imposed on the quark flavour-violating couplings. We then compare the resulting correlations with those present in generic models in which the latter couplings are arbitrary, subject to the constraints from ΔF = 2 processes, electroweak and collider data. Of particular interest are the correlations with ε′/ε and KL → μ+μ which limit the size of NP contributions to K+→π+νν¯ and KL→π0νν¯, depending on the Dirac structure of couplings and the relevant operators. But in MFV models also the constraint from Bs → μ+μ turns out to be important. We take into account the recent results from lattice QCD and large N approach that indicate ε′/ε in the SM to be significantly below the data. While in many models the enhancement of ε′/ε implies the suppression of KL→π0νν¯, we present two models in which ε′/ε and KL→π0νν¯ can be simultaneously enhanced relative to SM predictions. A correlation between K+→π+νν¯ and B → K(K*+μ, found by us in the simple models considered here, should be of interest for NA62 and LHCb experimentalists at CERN in the coming years. The one with B→K(K)νν¯ will be tested at Belle II.

Original languageEnglish
Article number166
Pages (from-to)1-33
Number of pages33
JournalJournal of High Energy Physics
Volume2015
Issue number11
DOIs
StatePublished - 1 Nov 2015

Keywords

  • B-Physics
  • Beyond Standard Model
  • Kaon Physics
  • Rare Decays

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