Angular momentum of the physical electron

The angular momentum of the physical electron, modelled as a Dirac fermion coupled to the electromagnetic field, is found to be hbar/2, the same as that of a bare Dirac fermion and independent of the size of the electric charge.Comment: revision, 3 pages pd

Quasi-Two-Body Decays of Nonstrange Baryons

We examine the decays of nonstrange baryons to the final states $\Delta\pi$, $N\rho$, $N\eta$, $N\eta^\prime$, $N\omega$, $N1/2^+(1440)\pi$, and $\Delta3/2^+(1600)\pi$, in a relativized pair-creation($^3P_0$) model which has been developed in a previous study of the $N\pi$ decays of the same baryon states. As it is our goal to provide a guide for the possible discovery of new baryon states at CEBAF and elsewhere, we examine the decays of resonances which have already been seen in the partial-wave analyses, along with those of states which are predicted by the quark model but which remain undiscovered. The level of agreement between our calculation and the available widths from the partial-wave analyses is encouraging.Comment: 41 pages, CEBAF-TH-93-1

Classical Simulation of Quantum Fields II

We consider the classical time evolution of a real scalar field in 2 dimensional Minkowski space with a $\lambda \phi^4$ interaction. We compute the spatial and temporal two-point correlation functions and extract the renormalized mass of the interacting theory. We find our results are consistent with the one- and two-loop quantum computation. We also perform Monte Carlo simulations of the quantum theory and conclude that the classical scheme is able to produce more accurate results with a fraction of the CPU time.Comment: 16 pages, 8 figures, now matches published versio

String Breaking in Quenched QCD

We present preliminary quenched results on a new operator for the investigation of string-breaking within SU(2)-colour QCD. The ground-state of a spatially-separated static-light meson-antimeson pair is a combination of a state with two distinct mesons, expected to dominate for large separations, and a state where the light-quarks have annihilated, which contributes for short distances. The crossover between these two regimes provides a measure of the string-breaking scale length.Comment: LATTICE98(confine), 3 pages, 4 figure

Algebraic Models of Hadron Structure II. Strange Baryons

The algebraic treatment of baryons is extended to strange resonances. Within this framework we study a collective string-like model in which the radial excitations are interpreted as rotations and vibrations of the strings. We derive a mass formula and closed expressions for strong and electromagnetic decay widths and use these to analyze the available experimental data.Comment: 60 pages, 8 figures, 30 tables, Annals of Physics (N.Y.), in pres

Strong decays of N∗(1535)N^{*}(1535) in an extended chiral quark model

The strong decays of the $N^{*}(1535)$ resonance are investigated in an extended chiral quark model by including the low-lying $qqqq\bar{q}$ components in addition to the $qqq$ component. The results show that these five-quark components in $N^{*}(1535)$ contribute significantly to the $N^{*}(1535)\to N\pi$ and $N^{*}(1535)\to N\eta$ decays. The contributions to the $N\eta$ decay come from both the lowest energy and the next-to-lowest energy five-quarks components, while the contributions to the $N\pi$ decay come from only the latter one. Taking these contributions into account, the description for the strong decays of $N^{*}(1535)$ is improved, especially, for the puzzling large ratio of the decays to $N\eta$ and $N\pi$.Comment: 6 pages, 1 figur

Crucial Dependence of ``Precarious'' and ``Autonomous'' phi^4s Upon the Normal-ordering Mass

Using the Gaussian wave-functional approach with the normal-ordering renormalization prescription, we show that for the (3+1)-dimensional massive lambda phi^4 theory, ``precarious'' and ``autonomous'' phi^4s can exist if and only if the normal-ordering mass is equal to the classical masses at the symmetrc and asymmetric vacua, respectively.Comment: 6 pages, no figures, Revtex file, accepted for publication in Mod. Phys. Lett.

Quark model predictions for K∗K^* photoproduction on the proton

The photoproduction of $K^*$ vector mesons is investigated in a quark model with an effective Lagrangian. Including both baryon resonance excitations and {\it t}-channel exchanges, observables for the reactions $\gamma p\to K^{*0}\Sigma^+$ and $\gamma p\to K^{*+}\Sigma^0$ are predicted, using the SU(3)-flavor-blind assumption of non-perturbative QCD.Comment: Revtex, 3 eps figures, revised version accepted by PRC Rapid Comm

Vector meson photoproduction studied in its radiative decay channel

We provide an analysis of vector meson photoproduction in the channel of the vector meson decaying into a pseudoscalar meson plus a photon, i.e. $V\to P\gamma$. It is shown that non-trivial kinematic correlations arise from the measurement of the $P\gamma$ angular distributions in the overall c.m. system in comparison with those in the vector-meson-rest frame. In terms of the vector meson density matrix elements, the implication of such kinematic correlations in the measurement of polarization observables is discussed. For the $\omega$ meson production, due to its relatively large branching ratios for $\omega\to\pi^0\gamma$, additional events from this channel may enrich the information about the reaction mechanism and improve the statistics of the recent measurement of polarized beam asymmetries by the GRAAL Collaboration. For $\phi\to \eta\gamma$, $\rho\to \pi\gamma$, and $K^*\to K\gamma$, we expect that additional information about the spin structure of the vector meson production vertex can be derived.Comment: Revtex, 14 pages, 2 eps figures; Version accepted by PR