Hidenori Sonoda

On the Validity of Chiral Perturbation Theory for Weak Hyperon Decays

The predictions of chiral perturbation theory for the weak non-leptonic decays of hyperons are examined beyond the leading order. For the S-wave amplitudes we find that the leading corrections to lowest order chiral perturbation theory preserve the vanishing of the Σ+ → nπ+ amplitude. However, the Lee-Sugawara relation gets a large correction indicating a breakdown of chiral perturbation theory for this relation. For the P-wave amplitudes we find that the leading corrections to lowest order chiral perturbation theory are large indicating a breakdown of chiral perturbation theory for the P-wave amplitudes. The weak semileptonic hyperon decays are determined by baryon matrix elements of the left-handed current. Corrections to the predictions of lowest order chiral perturbation theory for these matrix elements are computed. These corrections are very small.

Berry's phase in chiral gauge theories

Abstract Berrys phase in chiral gauge theories is computed. The result implies that the anomalous commutator of gauge transformations is the one previously obtained by Faddeev.

The Wess-Zumino term and the Hamiltonian formulation for anomalies

Abstract The phase change of a state vector of fermions after gauge transformations along a loop in G (3) , the space of three-dimensional gauge transformations, is calculated. It is given by the Wess-Zumino term. This simple formula enables us to compute the SU(2) anomaly of Witten. The U(1) gauge anomaly appears as a breakdown of unitarity.

Weak and Electromagnetic Properties of Hyperons in a Semiclassical Approximation

We discuss hyperon decays and hyperon magnetic moments using a chiral lagrangian where the baryons appear as solitons. Some relations are derived using the semiclassical approximation.

Decay of a dyon

Abstract Various electromagnetic properties of a non-abelian dyon are discussed in detail. Unlike in the previous works, a dyon of a finite size is considered. We show the dyon is unstable when it interacts with massless fermions. The lifetime is calculated numerically by solving the equations of motion and it is found to be 4 π 2 r M / e 2 ( r M is a radius of the dyon).

Bound states of a gauge boson by a magnetic monopole

Abstract We consider the massive gauge boson (W ± ) and the neutral Higgs particle (H) with zero angular momentum in the background field of a monopole for SU(2) gauge theory. The massive boson is found to form bound states. The maximum binding energy in the Prasad-Sommerfield limit is approximately 0.12 M ( M is the mass of W), independent of the gauge coupling constant. We also find that the amplitude of the process H + dyon W ± + dyon is nonvanishing even in the limit of zero gauge coupling constant, if we fix the mass of W.