551 research outputs found
Multichannel parametrization of \pi N scattering amplitudes and extraction of resonance parameters
We present results of a new multichannel partial-wave analysis for \pi N
scattering in the c.m. energy range 1080 to 2100 MeV. This work explicitly
includes \eta N and K \Lambda channels and the single pion photoproduction
channel. Resonance parameters were extracted by fitting partial-wave amplitudes
from all considered channels using a multichannel parametrization that is
consistent with S-matrix unitarity. The resonance parameters so obtained are
compared to predictions of quark models
A UV completion of scalar electrodynamics
In previous works, we constructed UV-finite and unitary scalar field theories
with an infinite spectrum of propagating modes for arbitrary polynomial
interactions. In this paper, we introduce infinitely many massive vector fields
into a U(1) gauge theory to construct a theory with UV-finiteness and
unitarity.Comment: 25 page
Gauge equivalence in QCD: the Weyl and Coulomb gauges
The Weyl-gauge ( QCD Hamiltonian is unitarily transformed to a
representation in which it is expressed entirely in terms of gauge-invariant
quark and gluon fields. In a subspace of gauge-invariant states we have
constructed that implement the non-Abelian Gauss's law, this unitarily
transformed Weyl-gauge Hamiltonian can be further transformed and, under
appropriate circumstances, can be identified with the QCD Hamiltonian in the
Coulomb gauge. We demonstrate an isomorphism that materially facilitates the
application of this Hamiltonian to a variety of physical processes, including
the evaluation of -matrix elements. This isomorphism relates the
gauge-invariant representation of the Hamiltonian and the required set of
gauge-invariant states to a Hamiltonian of the same functional form but
dependent on ordinary unconstrained Weyl-gauge fields operating within a space
of ``standard'' perturbative states. The fact that the gauge-invariant
chromoelectric field is not hermitian has important implications for the
functional form of the Hamiltonian finally obtained. When this nonhermiticity
is taken into account, the ``extra'' vertices in Christ and Lee's Coulomb-gauge
Hamiltonian are natural outgrowths of the formalism. When this nonhermiticity
is neglected, the Hamiltonian used in the earlier work of Gribov and others
results.Comment: 25 page
and form factors from QCD Sum Rules
The form factor for H = B and D mesons is evaluated in a QCD sum
rule calculation. We study the Borel sum rule for the three point function of
two pseudoscalar and one vector meson currents up to order four in the operator
product expansion. The double Borel transform is performed with respect to the
heavy meson momenta. We discuss the momentum dependence of the form factors and
two different approaches to extract the coupling constant.Comment: 12 pages, RevTeX including 6 figures in ps files, revised version
accepted for publication in Phys. Lett.
Parameterization dependence of T matrix poles and eigenphases from a fit to piN elastic scattering data
We compare fits to piN elastic scattering data, based on a Chew-Mandelstam
K-matrix formalism. Resonances, characterized by T-matrix poles, are compared
in fits generated with and without explicit Chew-Mandelstam K-matrix poles.
Diagonalization of the S matrix yields the eigenphase representation. While the
eigenphases can vary significantly for the different parameterizations, the
locations of most T-matrix poles are relatively stable.Comment: 6 pages, 3 figures, 1 tabl
Bethe-Salpeter equation with cross-ladder kernel in Minkowski and Euclidean spaces
Some results obtained by a new method for solving the Bethe-Salpeter equation
are presented. The method is valid for any kernel given by irreducible Feynman
graphs. The Bethe-Salpeter amplitude, both in Minkowski and in Euclidean
spaces, and the binding energy for ladder + cross-ladder kernel are found. We
calculate also the corresponding electromagnetic form factor.Comment: 4 pages, 3 figures. Contribution to the proceedings of the 18th
International IUPAP Conference on Few-Body Problems in Physics (FB18),
Santos, Brasil, August 21-26, 2006. To be published in Nucl. Phys.
A New Renormalization Scheme of Fermion Fields in Electroweak Standard Model
This paper has been withdrawn by the author,due a immature idea.Comment: 6 page
Equivariant Poincar\'e series of filtrations and topology
Earlier, for an action of a finite group on a germ of an analytic
variety, an equivariant -Poincar\'e series of a multi-index filtration in
the ring of germs of functions on the variety was defined as an element of the
Grothendieck ring of -sets with an additional structure. We discuss to which
extend the -Poincar\'e series of a filtration defined by a set of curve or
divisorial valuations on the ring of germs of analytic functions in two
variables determines the (equivariant) topology of the curve or of the set of
divisors
Baryon Magnetic Moments and Proton Spin: A Model with Collective Quark Rotation
We analyse the baryon magnetic moments in a model that relates them to the
parton spins , , , and includes a contribution
from orbital angular momentum. The specific assumption is the existence of a
3-quark correlation (such as a flux string) that rotates with angular momentum
around the proton spin axis. A fit to the baryon magnetic
moments, constrained by the measured values of the axial vector coupling
constants , , yields , , where the error is a theoretical
estimate. A second fit, under slightly different assumptions, gives , with no constraint on . The
model provides a consistent description of axial vector couplings, magnetic
moments and the quark polarization measured in deep
inelastic scattering. The fits suggest that a significant part of the angular
momentum of the proton may reside in a collective rotation of the constituent
quarks.Comment: 16 pages, 3 ps-figures, uses RevTeX. Abstract, Sec. II, III and IV
have been expande
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