Related papers: Pion loops in quenched Quantum Chromodynamics
We construct the generating functional of two flavor chiral perturbation theory including the effects of virtual photons in the one loop approximation. As an application, we calculate the electromagnetic corrections to the elastic $\pi\pi$…
We compute light and strange quark masses for quenched overlap fermions at two values of the gauge coupling. The renormalisation is done non-perturbatively. We test the predictions of quenched chiral perturbation theory for the quark mass…
We discuss how to formulate a staggered chiral perturbation theory. This amounts to a generalization of the Lee-Sharpe Lagrangian to include more than one flavor (i.e. multiple staggered fields), which turns out to be nontrivial. One loop…
In this talk, I address the comparison between results from lattice QCD computations and Chiral Perturbation Theory (ChPT). I briefly discuss how ChPT can be adapted to the much-used quenched approximation and what it tells us about the…
We develop quenched chiral perturbation theory for vector mesons made of light quarks, in the limit where the vector meson masses are much larger than the pion mass. We use this theory to extract the leading nonanalytic dependence of the…
Recently, the chiral logarithms predicted by quenched chiral perturbation theory have been extracted from lattice calculations of hadron masses. We argue that the deviations of lattice results from random matrix theory starting around the…
Chiral perturbation theory in the two-flavour sector allows one to analyse Green functions in QCD in a limit where the strange quark mass is considered to be large in comparison to the external momenta and to the light quark masses. In this…
We calculate meson correlators in the epsilon-regime within partially quenched chiral perturbation theory. The valence quark masses and sea quark masses can be chosen arbitrary and all non-degenerate. Taking some of the sea quark masses to…
We present a calculation of the finite volume corrections to meson masses and decay constants in three flavour Partially Quenched Chiral Perturbation Theory (PQChPT) through two-loop order in the chiral expansion for the flavour-charged (or…
We present a summary of our results for the light hadron spectrum in quenched lattice QCD and preliminary ones in two-flavor full QCD. For the quenched hadron spectrum we find that the mass formulae predicted by quenched chiral perturbation…
We show how quark-disconnected and quark-connected contributions to hadronic n-point functions can be written as independent correlators for which one can derive expressions in partially quenched chiral effective theory. As an example we…
We calculate the partition function of partially quenched chiral perturbation theory in the epsilon regime at next-to-leading order using the supersymmetry method in the formulation without a singlet particle. We include a nonzero imaginary…
Partial quenching allows one to consider correlation functions and amplitudes that do not arise in the corresponding unquenched theory. For example, physical $s$-wave pion scattering can be decomposed into $I=0$ and $2$ amplitudes, while,…
Chiral logarithms in $m_\pi^2$ are calculated at one loop, taking into account the leading contributions to flavor symmetry breaking due to staggered fermions. I treat both the full QCD case (2+1 light dynamical flavors) and the quenched…
Recently, we pointed out that chiral transformation properties of strong penguin operators change in the transition from unquenched to (partially) quenched QCD. As a consequence, new penguin-like operators appear in the (partially) quenched…
We introduce Feynman-like rules to compute quivers for two loops and higher for the coloured planar $\phi^3$ theory for winding number zero. We demonstrate this for a few cases. Then we extend this further to the case of $\phi^n$ theories,…
The chiral limit of finite-volume QCD is the $\epsilon$-regime of the theory. We discuss how this regime can be used for determining low-energy observables of QCD by means of comparisons between lattice simulations and quenched and…
We want to test the predictive power of Chiral Perturbation Theory (ChPT). In this work, we use the ChPT pion-pion scattering amplitude, including two loop contributions, and we obtain S- and P-wave low-energy phase shifts. We show that, by…
The existing Chiral Perturbation Theory (ChPT) calculations at order $p^6$ are reviewed. The principles of ChPT and how they are used are introduced. The main part is a review of the two- and three-flavour full two-loop calculations and…
We study the contributions from the connected and disconnected contraction diagrams to the pion-kaon scattering amplitude within the framework of SU$(4|1)$ partially-quenched chiral perturbation theory. Combining this with a finite-volume…