0000000000121477
AUTHOR
Gerhard F. Ecker
showing 12 related works from this author
The decays K→πl+l− beyond leading order in the chiral expansion
1998
We present a model-independent analysis of K+→π+l+l− and KS→π0l+l− decays, including K→3π unitarity corrections and a general decomposition of the dispersive amplitude. From the existing data on K+→π+e+e− we predict the ratio R = B(K+→π+μ+μ−)/B(K+→π+e+e−) to be larger than 0.23, in slight disagreement with the recent measurement R = 0.167±0.036. Consequences for the K±→π±e+e− charge asymmetries and for the KL→π0e+e− mode are also discussed.
Radiative Kaon decays and CP violation in chiral perturbation theory
1988
38 páginas, 11 figuras, 2 tablas.-- CERN-TH-4853-87 ; UWTHPH-1987-31.
Towards a consistent estimate of the chiral low-energy constants
2006
Guided by the large-N_C limit of QCD, we construct the most general chiral resonance Lagrangian that can generate chiral low-energy constants up to O(p^6). By integrating out the resonance fields, the low-energy constants are parametrized in terms of resonance masses and couplings. Information on those couplings and on the low-energy constants can be extracted by analysing QCD Green functions of currents both for large and small momenta. The chiral resonance theory generates Green functions that interpolate between QCD and chiral perturbation theory. As specific examples we consider the VAP and SPP Green functions.
Meson resonances, large N_c and chiral symmetry
2003
14 páginas, 2 tablas.-- arXiv:hep-ph/0305311v1
Reanalysis of pion pion phase shifts from K -> pi pi decays
2009
We re-investigate the impact of isospin violation for extracting the s-wave pion pion scattering phase shift difference delta_0(M_K) - delta_2(M_K) from K -> pi pi decays. Compared to our previous analysis in 2003, more precise experimental data and improved knowledge of low-energy constants are used. In addition, we employ a more robust data-driven method to obtain the phase shift difference delta_0(M_K) - delta_2(M_K) = (52.5 \pm 0.8_{exp} \pm 2.8_{theor}) degrees.
Isospin Violation inϵ′
2003
On the basis of a next-to-leading-order calculation in chiral perturbation theory, the first complete analysis of isospin breaking for direct $CP$ violation in ${K}^{0}\ensuremath{\rightarrow}2\ensuremath{\pi}$ decays is performed. We find a destructive interference between three different sources of isospin violation in the $CP$ violation parameter ${ϵ}^{\ensuremath{'}}$. Within the uncertainties of large-${N}_{c}$ estimates for the low-energy constants, the isospin violating correction for ${ϵ}^{\ensuremath{'}}$ is below 15%.
Electromagnetism in nonleptonic weak interactions
2000
16 páginas, 1 figura.-- PACS: 11.30.Rd; 13.25.Es; 13.40.Ks.-- arXiv:hep-ph/0006172v2
The role of resonances in chiral perturbation theory
1989
32 páginas, 2 figuras, 5 tablas.-- BUTP-88-18 ; CERN-TH-5185-88 ; CPT-2158 ; UWTHPH-1988-29.
Vector meson exchange in radiative kaon decays and chiral perturbation theory
1990
7 páginas, 4 figuras,1 tabla.
The longitudinal muon polarization in KL → μ+μ-
1991
17 páginas, 3 figuras, 1 tabla.-- CERN-TH-6035-91 ; UWTHPH-1991-9.
Kaon Decays in the Standard Model
2011
A comprehensive overview of kaon decays is presented. The Standard Model predictions are discussed in detail, covering both the underlying short-distance electroweak dynamics and the important interplay of QCD at long distances. Chiral perturbation theory provides a universal framework for treating leptonic, semileptonic and nonleptonic decays including rare and radiative modes. All allowed decay modes with branching ratios of at least 10^(-11) are analyzed. Some decays with even smaller rates are also included. Decays that are strictly forbidden in the Standard Model are not considered in this review. The present experimental status and the prospects for future improvements are reviewed.
〈VAP〉 Green function in the resonance region
2004
Abstract We analyze the 〈 V A P 〉 three-point function of vector, axial-vector and pseudoscalar currents. In the spirit of large N C , a resonance dominated Green function is confronted with the leading high-energy behaviour from the operator product expansion. The matching is shown to be fully compatible with a chiral resonance Lagrangian and it allows to determine some of the chiral low-energy constants of O ( p 6 ) .