575 research outputs found
Reanalysis of pion pion phase shifts from K -> pi pi decays
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.Comment: 8 page
Magnetic monopoles in U(1)_4 Lattice Gauge Theory with Wilson action
We construct the Euclidean Green functions for the soliton (magnetic
monopole) field in the U(1)_4 Lattice Gauge Theory with Wilson action. We show
that in the strong coupling regime there is monopole condensation while in the
QED phase the physical Hilbert space splits into orthogonal soliton sectors
labelled by integer magnetic charge.Comment: 13 pages, LaTeX 2.09 (revtex), submitted to Communications in
Mathematical Physic
Explicit generating functional for pions and virtual photons
We construct the explicit one-loop functional of chiral perturbation theory
for two light flavours, including virtual photons. We stick to contributions
where 1 or 2 mesons and at most one photon are running in the loops. With the
explicit functional at hand, the evaluation of the relevant Green functions
boils down to performing traces over the flavour matrices. For illustration, we
work out the pi+ pi- -> pi0 pi0 scattering amplitude at threshold at order p^4,
e^2p^2.Comment: 20 pages, 2 figures; version accepted for publication, minor
typographical changes, acknowledgments adde
K -> pi pi Electroweak Penguins in the Chiral Limit
We report on dispersive and finite energy sum rule analyses of the
electroweak penguin matrix elements in the chiral
limit. We accomplish the correct perturbative matching (scale and scheme
dependence) at NLO in alpha_s, and we describe two different strategies for
numerical evaluation.Comment: 4 pages, 2 figures. Contribution to QCD02, International Conference
on Quantum Chromo-Dynamics, Montpellier (France), July 2-9 200
The pionic beta decay in chiral perturbation theory
Within the framework of chiral perturbation theory with virtual photons and
leptons, we present an updated analysis of the pionic beta decay including all
electromagnetic contributions of order e**2 p**2. We discuss the extraction of
the Cabibbo-Kobayashi-Maskawa matrix element |Vud| from experimental data. The
method employed here is consistent with the analogous treatment of the Kl3
decays and the determination of |Vus|.Comment: 8 pages, 1 figure, latex file, uses EPJC macro
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