238 research outputs found
The strong-CP question in SU(3)_c X SU(3)_L X U(1)_N models
We analyze two recent models based on the gauge group
SU(3)SU(3)U(1) where each generation is not
anomaly-free, but anomaly cancels when three generations are taken into
account. We show that the most general Yukawa couplings of these models admit
of a Peccei-Quinn symmetry. This symmetry can be extended to the entire
Lagrangian by using extra fields in a very elegant way so that the resulting
axion can be made invisible.Comment: Latex, 8 pages, no figure
Long Duration Exposure Facility (LDEF) attitude measurements of the Interplanetary Dust Experiment
Analysis of the data from the Long Duration Exposure Facility (LDEF) Interplanetary Dust Experiment (IDE) sun sensors has allowed a confirmation of the attitude of LDEF during its first year in orbit. Eight observations of the yaw angle at specific times were made and are tabulated in this paper. These values range from 4.3 to 12.4 deg with maximum uncertainty of plus or minus 2.0 deg and an average of 7.9 deg. No specific measurements of pitch or roll were made but the data indicates that LDEF had an average pitch down attitude of less than 0.7 deg
A note on monopole moduli spaces
We discuss the structure of the framed moduli space of Bogomolny monopoles
for arbitrary symmetry breaking and extend the definition of its stratification
to the case of arbitrary compact Lie groups. We show that each stratum is a
union of submanifolds for which we conjecture that the natural metric is
hyperKahler. The dimensions of the strata and of these submanifolds are
calculated, and it is found that for the latter, the dimension is always a
multiple of four.Comment: 17 pages, LaTe
Topological Aspects of Gauge Fixing Yang-Mills Theory on S4
For an space-time manifold global aspects of gauge-fixing are
investigated using the relation to Topological Quantum Field Theory on the
gauge group. The partition function of this TQFT is shown to compute the
regularized Euler character of a suitably defined space of gauge
transformations. Topological properties of the space of solutions to a
covariant gauge conditon on the orbit of a particular instanton are found using
the isometry group of the base manifold. We obtain that the Euler
character of this space differs from that of an orbit in the topologically
trivial sector. This result implies that an orbit with Pontryagin number
\k=\pm1 in covariant gauges on contributes to physical correlation
functions with a different multiplicity factor due to the Gribov copies, than
an orbit in the trivial \k=0 sector. Similar topological arguments show that
there is no contribution from the topologically trivial sector to physical
correlation functions in gauges defined by a nondegenerate background
connection. We discuss possible physical implications of the global gauge
dependence of Yang-Mills theory.Comment: 13 pages, uuencoded and compressed LaTeX file, no figure
Torsion and the Gravitational Interaction
By using a nonholonomous-frame formulation of the general covariance
principle, seen as an active version of the strong equivalence principle, an
analysis of the gravitational coupling prescription in the presence of
curvature and torsion is made. The coupling prescription implied by this
principle is found to be always equivalent with that of general relativity, a
result that reinforces the completeness of this theory, as well as the
teleparallel point of view according to which torsion does not represent
additional degrees of freedom for gravity, but simply an alternative way of
representing the gravitational field.Comment: Version 2: minor presentation changes, a reference added, 11 pages
(IOP style
Gauge invariance and finite width effects in radiative two-pion tau lepton decay
The contribution of the rho^{\pm} vector meson to the tau -> pi pi nu gamma
decay is considered as a potential source for the determination of the magnetic
dipole moment of this light vector meson. In order to keep gauge-invariance of
the whole decay amplitude, a procedure similar to the fermion loop-scheme for
charged gauge bosons is implemented to incorporate the finite width effects of
the rho^{\pm} vector meson. The absorptive pieces of the one-loop corrections
to the propagators and electromagnetic vertices of the rho^{\pm} meson and
W^{\pm} gauge boson have identical forms in the limit of massless particles in
the loops, suggesting this to be a universal feature of spin-one unstable
particles. Model-dependent contributions to the tau -> pi pi nu gamma decay are
suppressed by fixing the two-pion invariant mass distribution at the rho meson
mass value. The resulting photon energy and angular distribution is relatively
sensitive to the effects of the rho magnetic dipole moment.Comment: 22 pages, 4 postscript figures, references and comments on relevance
of perturbative treatment of rho electromagnetic vertex are added, accepted
for pub. in Phys. Rev.
Isospin Violation in Chiral Perturbation Theory and the Decays \eta \ra \pi \ell \nu and \tau \ra \eta \pi \nu
I discuss isospin breaking effects within the standard model. Chiral
perturbation theory presents the appropriate theoretical framework for such an
investigation in the low--energy range. Recent results on the electromagnetic
contributions to the masses of the pseudoscalar mesons and the
amplitudes are reported. Using the one--loop formulae for the
form factors, rather precise predictions for the decay rates of can be obtained. Finally, I present an estimate of
the \tau \ra \eta \pi \nu branching ratio derived from the dominant meson
resonance contributions to this decay.Comment: 10 pages, latex, one figure available upon reques
The 331 model with right-handed neutrinos
We explore some more consequences of the electroweak
model with right-handed neutrinos. By introducing the mixing angle
, the {\it exact} physical eigenstates for neutral gauge bosons are
obtained. Because of the mixing, there is a modification to the coupling
proportional to . The data from the -decay allows us to fix the
limit for as . >From the neutrino
neutral current scatterings, we estimate a bound for the new neutral gauge
boson mass in the range 300 GeV, and from symmetry-breaking hierarchy a
bound for the new charged and neutral (non-Hermitian) gauge bosons are obtained.Comment: Slight changes in section 5, Latex, 16 page
Hyperon weak radiative decays in chiral perturbation theory
We investigate the leading-order amplitudes for weak radiative decays of
hyperons in chiral perturbation theory. We consistently include contributions
from the next-to-leading order weak-interaction Lagrangian. It is shown that
due to these terms Hara's theorem is violated. The data for the decays of
charged hyperons can be easily accounted for. However, at this order in the
chiral expansion, the four amplitudes for the decays of neutral hyperons
satisfy relations which are in disagreement with the data. The asymmetry
parameters for all the decays can not be accounted for without higher-order
terms. We shortly comment on the effect of the 27-plet part of the weak
interaction.Comment: 8 pages of REVTeX and using macro-package "feynman.tex" (available at
http://xxx.lanl.gov/ftp/hep-ph/papers/macros) for the 2 figure
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