A new look at the theory uncertainty of epsilon_K

Abstract

The observable epsilon_K is sensitive to flavor violation at some of the highest scales. While its experimental uncertainty is at the half percent level, the theoretical one is in the ballpark of 15%. We explore the nontrivial dependence of the theory prediction and uncertainty on various conventions, like the phase of the kaon fields. In particular, we show how such a rephasing allows to make the short-distance contribution of the box diagram with two charm quarks, eta_cc, purely real. Our results allow to slightly reduce the total theoretical uncertainty of epsilon_K, while increasing the relative impact of the imaginary part of the long distance contribution, underlining the need to compute it reliably. We also give updated bounds on the new physics operators that contribute to epsilon_K.

18 pages, 6 tables, 1 figure. v2: version accepted for publication on JHEP. v3: typos corrected, all results unchanged

References in corpus (11)

• Big-Bang Nucleosynthesis
• The Flavor of the Composite Pseudo-Goldstone Higgs
• Correlations among new CP violating effects in Delta F = 2 observables
• $B_{(s)}^0$-mixing matrix elements from lattice QCD for the Standard Model and beyond
• Epsilon_K at Next-to-Next-to-Leading Order: The Charm-Top-Quark Contribution
• $K\to \pi \pi$ $\Delta I=3/2$ decay amplitude in the continuum limit
• $K_L-K_S$ mass difference from lattice QCD
• Composite MFV and Beyond
• K^0-\bar K^0 mixing beyond the standard model and CP-violating electroweak penguins in quenched QCD with exact chiral symmetry
• Neutral kaon mixing beyond the standard model with nf=2+1 chiral fermions
• $K_L$ - $K_S$ mass difference computed with a 171 MeV pion mass

Cited by in corpus (9)

• Neutral Kaon Mixing Beyond the Standard Model with $n_f=2+1$ Chiral Fermions Part 1: Bare Matrix Elements and Physical Results
• Revisiting Kaon Physics in General $Z$ Scenario
• Standard-model prediction of ${\epsilon }_K$ with manifest CKM unitarity
• $B$ decay anomalies and dark matter from vectorlike confinement
• The Kinetic Heavy Quark Mass to Three Loops
• Exotic Electroweak Signals in Twin Higgs
• Revisiting Flavor and CP Violation in Supersymmetric SU(5) with Right-Handed Neutrinos
• $K^0-{\bar{K}}^0$ mixing in the minimal flavor-violating two-Higgs-doublet models
• Epsilon_K in the Standard Model and the kaon phase conventions