skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A new look at the theory uncertainty of ϵ K

Abstract

The observable ϵ 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, η cc , purely real. Our results allow to slightly reduce the total theoretical uncertainty of ϵ 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 ϵ K .

Authors:
 [1];  [2]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Centre National de la Recherche Scientifique (CNRS), Annecy-le-Vieux (France). Lab. D' Annecy-le-Vieux de Physique Theorique (LAPth)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1377439
Grant/Contract Number:
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 9; Journal ID: ISSN 1029-8479
Publisher:
Springer Berlin
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CP violation; kaon physics

Citation Formats

Ligeti, Z., and Sala, F.. A new look at the theory uncertainty of ϵ K. United States: N. p., 2016. Web. doi:10.1007/JHEP09(2016)083.
Ligeti, Z., & Sala, F.. A new look at the theory uncertainty of ϵ K. United States. doi:10.1007/JHEP09(2016)083.
Ligeti, Z., and Sala, F.. 2016. "A new look at the theory uncertainty of ϵ K". United States. doi:10.1007/JHEP09(2016)083. https://www.osti.gov/servlets/purl/1377439.
@article{osti_1377439,
title = {A new look at the theory uncertainty of ϵ K},
author = {Ligeti, Z. and Sala, F.},
abstractNote = {The observable ϵ 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, η cc , purely real. Our results allow to slightly reduce the total theoretical uncertainty of ϵ 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 ϵ K .},
doi = {10.1007/JHEP09(2016)083},
journal = {Journal of High Energy Physics (Online)},
number = 9,
volume = 2016,
place = {United States},
year = 2016,
month = 9
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share:
  • The geometry of torsion in the Riemann-Cartan (RC) theory can be described by an Abelian axial-vector field interacting with the axial-vector fermion current in a purely Riemannian background. On the basis of this observation we note that the Schwinger model formulated in curved spacetime can be interpreted as the two-dimensional version of the RC theory. In two dimensions as well as in four dimensions there is a one-parameter family of regulators that can be used to compute the axial anomaly. In four dimensions we set the value of the arbitrary parameter equal to zero and compute the axial anomaly, includingmore » counterterms, using Fujikawa's approach. The addition of the Wess-Zumino Lagrangian changes the original RC theory into a nonanomalous Abelian gauge theory of the torsion field. Guided by the analogy with the Schwinger model, we offer several forms of {ital L}{sub gravity} from which one can deduce the spin content of the quanta of torsion.« less
  • Gagne [Med. Phys. 16, 29-37 (1989)] has previously described a model for predicting the sensitivity and dose profiles in the slice-width (z) direction for CT scanners. The model, developed prior to the advent of multidetector CT scanners, is still widely used; however, it does not account for the effect of anode tilt on the penumbra or include the heel effect, both of which are increasingly important for the wider beams (up to 40 mm) of contemporary, multidetector scanners. Additionally, it applied only on (or near) the axis of rotation, and did not incorporate the photon energy spectrum. The improved modelmore » described herein transcends all of the aforementioned limitations of the Gagne model, including extension to the peripheral phantom axes. Comparison of simulated and measured dose data provides experimental validation of the model, including verification of the superior match to the penumbra provided by the tilted-anode model, as well as the observable effects on the cumulative dose distribution. The initial motivation for the model was to simulate the quasiperiodic dose distribution on the peripheral, phantom axes resulting from a helical scan series in order to facilitate the implementation of an improved method of CT dose measurement utilizing a short ion chamber, as proposed by Dixon [Med. Phys. 30, 1272-1280 (2003)]. A more detailed set of guidelines for implementing such measurements is also presented in this paper. In addition, some fundamental principles governing CT dose which have not previously been clearly enunciated follow from the model, and a fundamental (energy-based) quantity dubbed 'CTDI-aperture' is introduced.« less
  • Recently, a number of analytic prescriptions for computing the nonlinear matter power spectrum have appeared in the literature. These typically involve resummation or closure prescriptions which do not have a rigorous error control, thus they must be compared with numerical simulations to assess their range of validity. We present a direct side-by-side comparison of several of these analytic approaches, using a suite of high-resolution N-body simulations as a reference, and discuss some general trends. All of the analytic results correctly predict the behavior of the power spectrum at the onset of nonlinearity, and improve upon a pure linear theory descriptionmore » at very large scales. All of these theories fail at sufficiently small scales. At low redshift the dynamic range in scale where perturbation theory is both relevant and reliable can be quite small. We also compute for the first time the two-loop contribution to standard perturbation theory for cold dark matter models, finding improved agreement with simulations at large redshift. At low redshifts however the two-loop term is larger than the one-loop term on quasilinear scales, indicating a breakdown of the perturbation expansion. Finally, we comment on possible implications of our results for future studies. A software package implementing the methods presented here is available at http://mwhite.berkeley.edu/Copter.« less
  • We investigate the validity of effective field theory methods and the decoupling of heavy fields during inflation. Considering models of inflation in which the inflaton is coupled to a heavy (super-Hubble) degree of freedom initially in its vacuum state, we find that violations of decoupling are absent unless there is a breakdown of the slow-roll conditions. Next we allow for a temporary departure from inflation resulting in a period of non-adiabaticity during which effective field theory methods are known to fail. We find that the locality of the event and energy conservation lead to a tight bound on the sizemore » of the effects of the heavy field. We discuss the implications for the power spectrum and non-gaussianity, and comment on the connection with recent studies of the dynamics of multi-field inflation models. Our results further motivate the use of effective field theory methods to characterize cosmic inflation, and focus the question of observability of additional degrees of freedom during inflation to near the Hubble scale or below — as anticipated from the Wilsonian notions of decoupling and naturalness.« less