18 research outputs found
Chiral Perturbation Theory with Virtual Photons and Leptons
We construct a low-energy effective field theory which allows the full
treatment of isospin-breaking effects in semileptonic weak interactions. To
this end, we enlarge the particle spectrum of chiral perturbation theory with
virtual photons by including also the light leptons as dynamical degrees of
freedom. Using super-heat-kernel techniques, we determine the additional
one-loop divergences generated by the presence of virtual leptons and give the
full list of associated local counterterms. We illustrate the use of our
effective theory by applying it to the decays pi -> l nu_{l} and K -> l nu_{l}.Comment: 22 pages, no figure
Radiative corrections to K_{l3} decays
We present a complete calculation of the K_{l3} decays K^+ --> pi^0 l^+ nu_l
and K^0 --> pi^- l^+ nu_l to O(p^4, (m_d-m_u) p^2, e^2 p^2) in chiral
perturbation theory with virtual photons and leptons. We introduce the concept
of generalized form factors and kinematical densities in the presence of
electromagnetism, and propose a possible treatment of the real photon emission
in K^+_{l3} decays. We illustrate our results by applying them to the
extraction of the Kobayashi--Maskawa matrix element |V_{us}| from the
experimental K^+_{e3} decay parameters.Comment: 13 page
Strings, monopoles, and meson states
Dirac's formulation of the monopole theory modified by an additional mass term for the gauge field has been considered as a possible simplified model for quark binding. We discuss methods for the consistent regularization of the infinities present in the resulting action and equations of motion. In this way we are led to an action which is the same as that suggested by previous authors. We show that the expression for the energy of the modified action still has infinities unless the mass of the gauge field is infinite. Thus the regularization procedure is incomplete when the gauge field has finite mass. Applications of the regularized model to charmonium and other meson states are discussed
Isospin Violation in Chiral Perturbation Theory and the Decays \eta \ra \pi \ell \nu and \tau \ra \eta \pi \nu
I discuss isospin breaking effects within the standard model. Chiral
perturbation theory presents the appropriate theoretical framework for such an
investigation in the low--energy range. Recent results on the electromagnetic
contributions to the masses of the pseudoscalar mesons and the
amplitudes are reported. Using the one--loop formulae for the
form factors, rather precise predictions for the decay rates of can be obtained. Finally, I present an estimate of
the \tau \ra \eta \pi \nu branching ratio derived from the dominant meson
resonance contributions to this decay.Comment: 10 pages, latex, one figure available upon reques
The Electromagnetic Interaction in Chiral Perturbation Theory
We investigate electromagnetic effects in the framework of chiral
perturbation theory. Using a completely independent method, we confirm Urech's
results for the divergences of the one--loop functional in the electromagnetic
sector. We perform a one--loop analysis of all () and the form factors ,
, including a systematic treatment of the \cO(e^2p^2)
contributions in the mesonic part. We illustrate our results by several
numerical estimates.Comment: 15 pages, late
CP violation
The salient features of CP-violating interactions in the standard electroweak
theory and in a few of its popular extensions are discussed. Moreover a brief
overview is given on the status and prospects of searches for CP
non-conservation effects in low and high energy experiments.Comment: 28 pages, Lectures given at the 37th Winter School on Particle
Physics, Schladming, Austria, 199