TY - JOUR
T1 - Evading the Grossman-Nir bound with ∆I = 3/2 new physics
AU - He, Xiao Gang
AU - Ma, Xiao Dong
AU - Tandean, Jusak
AU - Valencia, German
PY - 2020/8/1
Y1 - 2020/8/1
N2 - Rare kaon decays with missing energy, K → π+Emiss, have received considerable attention because their rates can be calculated quite precisely within the standard model (SM), where the missing energy is carried away by an undetected neutrino- antineutrino pair. Beyond the SM, clean theoretical predictions can also be made regarding these processes. One such prediction is the so-called Grossman-Nir (GN) bound, which states that the branching fractions of the KL and K+ modes must satisfy the relation ℬ(KL→π0+Emiss)<∼4.3ℬ(K+→π++Emiss) and applies within and beyond the SM, as long as the hadronic transitions change isospin by ∆I = 1/2. In this paper we extend the study of these modes to include new-physics scenarios where the missing energy is due to unobserved lepton-number-violating neutrino pairs, invisible light new scalars, or pairs of such scalars. The new interactions are assumed to arise above the electroweak scale and described by an effective field theory. We explore the possibility of violating the GN bound through ∆I = 3/2 contributions to the K → π transitions within these scenarios and find that large violations are only possible in the case where the missing energy is due to an invisible light new scalar.
AB - Rare kaon decays with missing energy, K → π+Emiss, have received considerable attention because their rates can be calculated quite precisely within the standard model (SM), where the missing energy is carried away by an undetected neutrino- antineutrino pair. Beyond the SM, clean theoretical predictions can also be made regarding these processes. One such prediction is the so-called Grossman-Nir (GN) bound, which states that the branching fractions of the KL and K+ modes must satisfy the relation ℬ(KL→π0+Emiss)<∼4.3ℬ(K+→π++Emiss) and applies within and beyond the SM, as long as the hadronic transitions change isospin by ∆I = 1/2. In this paper we extend the study of these modes to include new-physics scenarios where the missing energy is due to unobserved lepton-number-violating neutrino pairs, invisible light new scalars, or pairs of such scalars. The new interactions are assumed to arise above the electroweak scale and described by an effective field theory. We explore the possibility of violating the GN bound through ∆I = 3/2 contributions to the K → π transitions within these scenarios and find that large violations are only possible in the case where the missing energy is due to an invisible light new scalar.
KW - Beyond Standard Model
KW - Chiral Lagrangians
KW - Effective Field Theories
KW - Kaon Physics
UR - http://www.scopus.com/inward/record.url?scp=85089226713&partnerID=8YFLogxK
U2 - 10.1007/JHEP08(2020)034
DO - 10.1007/JHEP08(2020)034
M3 - Article
AN - SCOPUS:85089226713
SN - 1029-8479
VL - 2020
JO - Journal of High Energy Physics
JF - Journal of High Energy Physics
IS - 8
M1 - 34
ER -