Eric Umland

Gluonic nucleons in a valon bag model

Abstract Two isomers of the nucleon, consisting of three 1S quarks and a transverse electric gluon, are predicted by the bag model to exist at masses around 1600 MeV. Mixing of these states with the nucleons seems unacceptably large. With this motivation we reformulate the problem in terms of valons — dressed quark and gluon single-particle eigenstates of (part of) the QCD bag hamiltonian. Now composed of valons, the nucleon and gluonic nucleons are decoupled, thereby retaining previous descriptions of the nucleon. One isomer should be visible in πN elastic scattering and might be the N∗ (1710).

Nucleon recurrences in the cloudy bag model

Abstract The spectrum of nucleon recurences in the 1–2 GeV region is analyzed in the context of the Cloudy Bag Model. The (1470) Roper resonance is required to be two (1s) 2 2s three quark states split by ∼ 100 MeV. The P 11 (1710) can be accomodated as a (1s) 3 + TE gluon state.

Chiral invariance in the soliton bag model

Abstract The soliton bag model of quark confinement is shown to give the same pionic coupling as the cloudy bag model, explicitly independent of details of the soliton field. The Goldberger-Treiman relation is satisfied in this development.

NN and πD reduced widths of dibaryon resonances

Abstract The reduced widths of the conjectured J = 2 + (2180) and J = 3 − (2220) dibaryon resonances in NN and πD channels are calculated.

fπΔΔ and the cloudy bag model

Abstract The cloudy bag model predicts f πΔΔ a factor of two greater than the experimental results deduced by Arndt et al. Possible explanations are explored.

Polarized cross section for the reaction p↑+p → pπ+n

We have measured the spin dependent fifth differential cross section for the reaction p↑+p → pπ+n through the 3/2, 3/2 resonances in a kinematically complete experiment at 800 MeV.

Calculation of asymmetries and cross sections for the reaction p↑p → pπ+n

The recent kinematically‐complete, polarized beam experiment of Hancock et al.1 performed at LAMPF, provides high quality data on spin up and spin down differential cross sections (dσ/dΩpdΩπdPp) for the reaction p↑p → pπ+n and is a stringent test of single pion production (SPP) theories at medium energies.