65 research outputs found
Composite photon and W^\pm, Z^0 vector bosons from a top-condensation model at fixed v = 247 GeV
Starting from the historical Fermi four-fermion low-energy effective
electroweak interactions Lagrangian for the third generation of quarks,
augmented by an NJL type interaction responsible for dynamical symmetry
breaking and heavy quark mass generation, and fixing the scalar (Higgs) field
v.e.v. at v = 247 GeV, we show that: (1) heavy quark bound states Q\bar Q with
quantum numbers of the W^\pm bosons exist for arbitrarily weak (positive)
vector coupling G_F, so long as the quark mass is sufficiently large; (2) a
massive composite neutral vector boson (Z^0) appears; (3) a massless composite
parity-conserving neutral vector boson (\gamma) appears, the composite
Higgs-Kibble ghosts decouple from the quarks and other particles, the
longitudinal components of the vector boson propagators vanish, as G_F \to
G_F^expt = 1/(\sqrt2 v^2), which also implies that the cutoff \Lambda \to
\infty. Thus, the Fermi interaction model is equivalent to a locally gauge
invariant theory but with definite values of coupling constants and masses. The
model discussed here was chosen for illustrative purposes and is not equivalent
to the Standard Model.Comment: 9 pages, 1 eps figur
Bound state in the vector channel of the extended Nambu--Jona-Lasinio model at fixed f_\pi
We show that, as a consequence of fixing f_\pi = 93 MeV: (1) a bound state
pole in the J^P = 1^- scattering amplitude of the ENJL model exists for
arbitrarily weak (positive) vector coupling G_2 so long as the constituent
quark mass is sufficiently large; (2) there is a bound state for any quark mass
when G_2 \geq 0.6/(8 f_\pi^2); (3) this bound state becomes massless at G_2 =
1/(8 f_\pi^2) and a tachyon for G_2 exceeding it. We show by way of an example
that the model has no trouble fitting the \rho meson mass simultaneously with
other observables.Comment: 9 pages, 2 (eps) figures, to appear in PL
U_A(1) symmetry breaking, scalar mesons and the nucleon spin problem in an effective chiral field theory
We establish a relationship between the scalar meson spectrum and the symmetry-breaking 't Hooft interaction on one hand and the constituent
quark's flavor-singlet axial coupling constant on the other,
using an effective chiral quark field theory. This analysis leads to the new
sum rule , where are the observed pseudoscalar mesons, is the strange
scalar meson at 1430 MeV and are "the eighth and the ninth"
scalar mesons. We discuss the relationship between the constituent quark
flavor-singlet axial coupling constant and the nucleon one
(``nucleon's spin content'') in this effective field theory.
We also relate , as well as the flavour-octet constituent quark
axial coupling constant to vector and axial-vector meson
masses in general as well as in the tight-binding limit.Comment: 16 pages, 3 figures, RevTex, to appear in Nucl.Phys.
A Comment on General Formulae for Polarization Observables in Deuteron Electrodisintegration and Linear Relations
We establish a simple, explicit relation between the formalisms employed in
the treatments of polarization observables in deuteron two-body
electrodisintegration published by Arenh\"ovel, Leidemann, and Tomusiak in
Few-Body Systems {\bf 15}, 109 (1993) and the results of the present authors
published in Phys.~Rev.~C {\bf 40}, 2479 (1989). We comment on the overlap
between the two sets of results.Comment: 9 pages, no figure
Reply to Comment on "Hara's theorem in the constituent quark model"
In the preceding Comment it is alleged that a "hidden loophole" in the proof
of Hara's theorem has been found, which purportedly invalidates the conclusions
of the paper commented upon. I show that there is no such loophole in the
constituent quark model, and that the "counterexample" presented in the Comment
is not gauge invariant.Comment: 5 pages, reply to lanl e-print hep-ph/970923
Linear Sigma model in the Gaussian wave functional approximation II: Analyticity of the S-matrix and the effective potential/action
We show an explicit connection between the solution to the equations of
motion in the Gaussian functional approximation and the minimum of the
(Gaussian) effective potential/action of the linear model, as well as
with the N/D method in dispersion theory. The resulting equations contain
analytic functions with branch cuts in the complex mass squared plane.
Therefore the minimum of the effective action may lie in the complex mass
squared plane. Many solutions to these equations can be found on the second,
third, etc. Riemann sheets of the equation, though their physical
interpretation is not clear. Our results and the established properties of the
S-matrix in general, and of the N/D solutions in particular, guide us to the
correct choice of the Riemann sheet. We count the number of states and find
only one in each spin-parity and isospin channel with quantum numbers
corresponding to the fields in the Lagrangian, i.e. to Castillejo-Dalitz-Dyson
(CDD) poles. We examine the numerical solutions in both the strong and weak
coupling regimes and calculate the Kallen-Lehmann spectral densities and then
use them for physical interpretation.Comment: 14 pages, 4 ps figures, to appear in Nucl. Phy
Goldstone Theorem in the Gaussian Functional Approximation to the Scalar Theory
We verify the Goldstone theorem in the Gaussian functional approximation to
the theory with internal O(2) symmetry. We do so by reformulating
the Gaussian approximation in terms of Schwinger-Dyson equations from which an
explicit demonstration of the Goldstone theorem follows directly.Comment: 11 page
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