Related papers: epsilon'/epsilon and Chiral Dynamics
A simulation of lattice QCD at (or even below) the physical pion mass is feasible on a small lattice size of \sim 2 fm. The results are, however, subject to large finite volume effects. In order to precisely understand the chiral behavior…
A recent lattice prediction of $\varepsilon'/\varepsilon$, with a 2.1 $\sigma$ deviation from the experimental value, has triggered several studies of possible contributions from physics beyond the Standard Model. We have recently updated…
We present a reanalysis of direct CP violation in the decay K_L -> pi^+ pi^- gamma. We point out an existing discrepancy between the theoretical and experimental definitions of epsilon'_{+-gamma}. Adopting the experimental definition of…
We review the current status of calculations of the two pion decays of the kaon using the first-principles methods of lattice gauge theory and the significant challenges that these calculations pose. While a calculation with controlled…
The pion mass difference generates a pronounced cusp in K --> 3 pi decays, the strength of which is related to the pi pi S-wave scattering lengths. We apply an effective field theory framework developed earlier to evaluate the amplitudes…
Recent experimental improvements on K-decay data allow for a precise extraction of the strangeness-changing scalar K pi form factor and the related strange scalar spectral function. On the basis of this scalar as well as the corresponding…
During the last four years several parameters relevant for the analysis of the CP-violating ratio epsilon'/epsilon improved and/or changed significantly. In particular, the experimental value of epsilon'/epsilon and the strange quark mass…
In the framework of heavy baryon chiral perturbation theory, we give thIn the framework of heavy baryon chiral perturbation theory, we give the chiral expansion for the $\pi N \to \pi \pi N$ threshold amplitudes $D_1$ and $D_2$ to quadratic…
Lattice QCD studies of hadron-hadron interactions are performed by computing the energy levels of the system in a finite box. The shifts in energy levels proportional to inverse powers of the volume are related to scattering parameters in a…
We augment the chiral Lagrangian by an isosinglet scalar and compute the one-loop radiative corrections to the pion mass and decay constant, as well as the scalar mass. The calculations are carried out for different patterns of chiral…
A lattice computation of the leading-order hadronic contribution to the muon anomalous magnetic moment can potentially help reduce the error on the Standard Model prediction for this quantity, if sufficient control of all systematic errors…
A recent lattice evaluation of $\varepsilon'/\varepsilon$, finding a 2.1 $\sigma$ deviation from the experimental value, has revived the old debate about a possible $\varepsilon'/\varepsilon$ anomaly. The unfounded claims of a too low…
Using the analysis of ChPT to two loops, we perform an error analysis of the threshold and low energy parameters, based on the uncertainties for the one loop low energy parameters and the resonance saturation mechanism. Different sets of…
Isospin-breaking effects, in particular those associated with electroweak-penguin contributions and pi0-eta,eta' mixing, have long been known to affect the Standard Model prediction of Re(epsilon'/epsilon) in a significant manner. We have…
An investigation is performed of all non-leptonic kaon decays sensitive to the chiral anomaly. Within the framework of chiral perturbation theory, there are two classes of anomalous amplitudes at $O(p^4)$: reducible and direct…
I shortly review the present status of the theoretical estimates of eps'/eps. I consider a few aspects of the theoretical calculations which may be relevant in understanding the present experimental results. In particular, I discuss the…
Dynamical chiral symmetry breaking is described within the linear sigma model of QCD coupled to quarks. The main technical tool used for this intrinsically non--perturbative problem is an exact renormalization group equation for the quantum…
I summarize the results of the complete one--loop chiral perturbation theory calculation performed recently. It is shown that it allows to accurately pin down the isospin two, S--wave $\pi \pi$ scattering length $a_0^2$. On the other hand,…
The leading non-Coulombic electromagnetic contributions to pi pi s-wave scattering lengths are computed in Chiral Perturbation Theory. It is shown that these corrections are zeroth order in the chiral expansion and associated with…
We consider the contribution to $K \rightarrow 2 \pi$ decays from the non-diagonal $s \ra d$ quark transition amplitude. First, we calculate the most important part of the $s \rightarrow d$ transition, the so-called self-penguin amplitude…