TY - JOUR
T1 - (Formula Presented) and ε′/ε in simplified new physics models
AU - Buras, Andrzej J.
AU - Buttazzo, Dario
AU - Knegjens, Robert
N1 - Publisher Copyright:
© 2015, The Author(s).
PY - 2015/11/1
Y1 - 2015/11/1
N2 - 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+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.
AB - 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+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.
KW - B-Physics
KW - Beyond Standard Model
KW - Kaon Physics
KW - Rare Decays
UR - http://www.scopus.com/inward/record.url?scp=84948772482&partnerID=8YFLogxK
U2 - 10.1007/JHEP11(2015)166
DO - 10.1007/JHEP11(2015)166
M3 - Article
AN - SCOPUS:84948772482
SN - 1126-6708
VL - 2015
SP - 1
EP - 33
JO - Journal of High Energy Physics
JF - Journal of High Energy Physics
IS - 11
M1 - 166
ER -