108 research outputs found
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 ,
, , , , , and
, in a relativized pair-creation() model which has
been developed in a previous study of the 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 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
Strong decays of in an extended chiral quark model
The strong decays of the resonance are investigated in an
extended chiral quark model by including the low-lying components
in addition to the component. The results show that these five-quark
components in contribute significantly to the and decays. The contributions to the decay
come from both the lowest energy and the next-to-lowest energy five-quarks
components, while the contributions to the decay come from only the
latter one. Taking these contributions into account, the description for the
strong decays of is improved, especially, for the puzzling large
ratio of the decays to and .Comment: 6 pages, 1 figur
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
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 photoproduction on the proton
The photoproduction of 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 and 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. . It is shown that non-trivial kinematic correlations arise from the
measurement of the 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
meson production, due to its relatively large branching ratios for
, 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 , , and , 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
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