Robert A. Williams

Tensor glueball photoproduction and decay

Abstract Using vector meson dominance (VMD), tensor glueball photoproduction cross sections, asymmetries and widths are calculated. The predicted hadronic V V ′ decays are comparable for different vector meson ( V = ρ , ω and ϕ ) channels with the ωϕ width the largest but the radiative ωγ and ϕγ decays are suppressed relative to ργ by over a factor of 2. This decay profile is distinct from typical meson branching rates and may be a useful glueball detection signature. Results are compared to a previous VMD scalar glueball study.

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.

Coupled channel analysis of S -wave π π and K K ¯ photoproduction

We present a coupled channel partial wave analysis of nondiffractive S-wave pi+ pi- and K+ K- photoproduction focusing on the KK threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both pion-pion and kaon-antikaon channels. Our results indicate that these processes are experimentally measurable and valuable information on the f0(980) resonance structure can be obtained.

Probing Proton Strangeness with Time-Like Virtual Compton Scattering

We document that p(gamma,e+e-)p measurements will yield new, important information about the off-shell time-like nucleon form factors, especially in the phi meson region (q{sup 2} = M{sup 2}{sub {phi}}) governing the phi N couplings g{sup V,T}{sub {phi}NN}. Calculations for p(gamma,e+e-)p, utilizing vector meson dominance, predict measurable phi enhancements at high |t| compared to the expected phi background production from pi, eta and Pomeron exchange. The phi form factor contribution generates a novel experimental signature for OZI violation and the proton strangeness content. The phi N couplings are determined independently from a combined analysis of the neutron electric form factor and recent high |t| phi photoproduction. The pi, eta and Pomeron transition form factors are also predicted and the observed pi and eta transition moments are reproduced.

PROBING NUCLEON STRANGENESS USING VECTOR MESON DOMINANCE

Abstract Calculations for N ( π , e + e − ) N reactions are reported to motivate measurements of the nucleon time-like form factors in the φ meson mass region. Using vector meson dominance and a field theoretical model which describes pion photoproduction data, crossing predictions for N ( π , e + e − ) N are detailed exhibiting dramatic, several order of magnitude enhancements from φN coupling in the nucleon form factors. These narrow, dual peaked resonances provide a novel experimental signature for OZI violation and the related strangeness content of the nucleon. A low energy analysis of the limited p ( γ , φ ) p data is also presented using a similar dynamic model and φN coupling.

Electromagnetic Probe of Nucleon Strangeness

We continue our strangeness studies with new calculations for the nucleon time-like form factors and probing lepton pair production process N(π,e+e−)N. Using a recent value for the φN coupling constant obtained from our analysis of limited p(γ, φ))p data, we again document a several order of magnitude e + e − production resonant cross section structure. This dramatic φ peak follows from vector meson dominance and provides an interesting experimental signature for OZI violation and the strangeness content of the nucleon.

Elastic meson form factors with modified vector resonance propagators

Sakurai{close_quote}s SU{sub F}(3) universality symmetry is employed to provide a unified description of pseudoscalar meson nonet elastic form factors calculated using a modified vector meson dominance (VMD) formalism. We incorporate excited resonances with modified propagators derived from analyticity and elastic unitarity, employing a single channel N/D approximation to model nonresonant meson exchange contributions. Existing spacelike and timelike data for {pi}{sup +}, K{sup +}, and K{sup 0} mesons indicate that finite width corrections to the {rho} propagator and couplings are essential for a precise theoretical description in the VMD framework. Our analysis verifies that existing data cannot rule out the possible existence of two unconfirmed resonances (one narrow isoscalar and one broad isovector) just below and above the p{bar p} threshold previously suggested to explain the anomalous features observed in timelike G{sub M}{sup p} LEAR and G{sub E}{sup n} FENICE data. {copyright} {ital 1998} {ital The American Physical Society}

Coupled Channel Analysis of S-Wave Pion-Pion and Kaon-Kaon Photoproduction

We present a coupled channel partial wave analysis of nondiffractive S-wave pi+ pi- and K+ K- photoproduction focusing on the KK threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both pion-pion and kaon-antikaon channels. Our results indicate that these processes are experimentally measurable and valuable information on the f0(980) resonance structure can be obtained.

Coupled channel analysis of S wave pi pi and K anti-K photoproduction

We present a coupled channel partial wave analysis of nondiffractive S-wave pi+ pi- and K+ K- photoproduction focusing on the KK threshold. Final state interactions are included. We calculate total cross sections, angular and effective mass distributions in both pion-pion and kaon-antikaon channels. Our results indicate that these processes are experimentally measurable and valuable information on the f0(980) resonance structure can be obtained.

Nucleon strangeness content through vector meson dominance

We document that N(π,e+e−)N measurements will provide new information about the nucleon time-like form factor in the φ meson region including the value of the φN coupling constant, gφNN. Using vector meson dominance and a field theoretical model which describes pion photoproduction data, we report crossing predictions for the N(π,e+e−)N cross section which exhibit dramatic, several order of magnitude enhancements from φN coupling in the nucleon form factors. These narrow, dual peaked resonances provide a novel experimental signature for OZI violation and the related strangeness content of the nucleon.