Warren W. Buck

The axial anomaly and the dynamical breaking of chiral symmetry in the γ∗π0 → γ reaction

Using the quark triangle diagram for the Adler-Bell-Jackiw axial anomaly, we calculate the form factor for the {gamma}{sup *}{pi}{sup 0}{yields}{gamma} transition. This form factor depends on the quark mass, and we predict the right behavior with m{sub q}{approx_equal}250 MeV, the same quark mass generated by the dynamical breaking of chiral symmetry through a Nambu-Jona-Lasinio mechanism.

Charged-Particle Transport in One Dimension

A numerical solution to high-energy charged-particle transport is found by evaluation of the integral equations obtained by inverting the Boltzmann differential operator. An algorithm has been written for either continuous or discrete spectra at the boundary, which allows efficient and accurate evaluation of this rather complicated problem. Present results are compared with analytic solutions based on the perturbation theory.

Elastic charge form factors for K mesons

Abstract The elastic charge form factors for the charged K+ and neutral K0 are presented. The model employed makes use of solutions of the coupled Bethe-Salpeter and Schwinger-Dyson equations. This covariant model provides good predictions for the pions elastic charge and transition form factor, and here we extend the model to include strange quarks. The results for the kaon are in good agreement with the available data. This model is partially motivated by the expectation of precision data from CEBAF approved experiment E-93-018. The non vanishing K0 form factor is due to the mass difference between the strange and down quarks.

Covariant quark model of pion structure

A relativistic quark model wave function of the pion is obtained from a fit to the experimental data, including the charge radius, charge form factor and weak decay constant.The results are quite stable for different choices of quark mass.The two-photon decay width of the neutral pion and the asymptotic form factor for the gamma*+ pi^0 -> gamma transition are estimated.

New constraints on dispersive form factor parametrizations from the timelike region

The authors generalize a recent model-independent form factor parameterization derived from rigorous dispersion relations to include constraints from data in the timelike region. These constraints dictate the convergence properties of the parameterization and appear as sum rules on the parameters. They further develop a new parameterization that takes into account finiteness and asymptotic conditions on the form factor, and use it to fit to the elastic {pi} electromagnetic form factor. They find that the existing world sample of timelike data gives only loose bounds on the form factor in the spacelike region, but explain how the acquisition of additional timelike data or fits to other form factors are expected to give much better results. The same parameterization is seen to fit spacelike data extremely well.

Unified description of kaon electroweak form factors

A calculation of the semileptonic decays of the kaon (K{sub l3}) is presented. The results are direct predictions of a covariant model of the pion and kaon introduced earlier by Ito, Buck, Gross. The weak form factors for K{sub l3} are predicted with absolutely no parameter adjustments of the model. The authors obtained for the form factor parameters: f{sub {minus}}(q{sup 2}=m{sub l}{sup 2})/f{sub +}(q{sup 2}=m{sub l}{sup 2})={minus}0.28 and {lambda}{sub +}= 0.028, both within experimental error bars. Connections of this approach to heavy quark symmetry will also be discussed.

Relativistic Quark Clustering in the gamma gamma -> pi^+ pi^- and pi^0 pi^0 reactions

Cross section for pion pair production by photon-photon collisions are estimated near the threshold using a relativitic quark clustering model.A realistic qq wave function of the pion was determined by fitting the pion charge form factor up to q^2 = 4 ~ 6 GeV^2/c^2, the weak decay constant and the pion charge radius.The composite structure of the pion provides a simple explanation for the energy dependence and magnitudes of pi^+pi^- and pi^0 pi^0 pair productions.