427 research outputs found
A simple SU(5) model with unification near the Planck scale
We study unification in the SU(5) model with an extra Dirac multiplet in the
representation. After spontaneous symmetry breaking we have at low
energies a singlet, a colorless triplet and a neutral color-octet. All other
particles can be taken at the unification scale. This combination leads to a
unification very near the Planck scale. The triplet is light, its neutral
component is a dark matter candidate. The model is in agreement with a recently
derived anomaly condition, that implies that the number of (Weyl)-fermions has
to be a multiple of 16.Comment: 6 page
Resonance in Strong WW Rescattering in Massive SU(2) Gauge Theory
We investigate the effects of WW rescattering through strong anomalous
four-vector boson couplings. In the I=1, J=1 channel, we find a resonance with
a mass of approximately 200 GeV and a width of less than 12 GeV. In an
application to pion physics we find a small correction to the KSRF relation.Comment: 21 pages, extended discussion, some minor change
Non--decoupling, triviality and the parameter
The dependence of the parameter on the mass of the Higgs scalar and
the top quark is computed non--perturbatively using the expansion in
the standard model. We find an explicit expression for the parameter
that requires the presence of a physical cutoff. This should come as no
surprise since the theory is presumably trivial. By taking this cutoff into
account, we find that the parameter can take values only within a
limited range and has finite ambiguities that are suppressed by inverse powers
of the cutoff scale, the so called ``scaling--violations". We find that large
deviations from the perturbative results are possible, but only when the cutoff
effects are also large.Comment: 16pp, Figures NOT included, harvmac, minor modifications incl.
wording, refs., UCLA/92/TEP/23,OHSTPY-HEP-T-92-00
Interpretation of Precision Measurements in the Strongly Interacting Limit of the Standard Electroweak Model
Strong rescattering corrections to one-loop contributions to the parameters
of the standard electroweak model are considered.Comment: 12 page
Heavy Fermion Screening Effects and Gauge Invariance
We show that the naively expected large virtual heavy fermion effects in low
energy processes may be screened if the process under consideration contains
external gauge bosons constrained by gauge invariance. We illustrate this by a
typical example of the process . Phenomenological
implications are also briefly indicated.Comment: a miss-print fixed, 7 pages, LaTex, no figure
Corrections to oblique parameters induced by anomalous vector boson couplings
We study quadratically divergent radiative corrections to the oblique
parameters at LEP1 induced by non-standard vector boson self-couplings. We work
in the Stueckelberg formalism and regulate the divergences through a
gauge-invariant higher derivative scheme. Using consistency arguments together
with the data we find a limit on the anomalous magnetic moment Delta kappa of
the W-boson, |Delta kappa| <= 0.26.Comment: 32 pages, LaTeX; cross reference corrected, minor beautifications,
version to be published in Phys.Rev.
Ongoing mumps outbreak in a student population with high vaccination coverage, Netherlands, 2010.
Since December 2009, mumps incidence has increased in the Netherlands. As of 20 April 2010, 172 cases have been notified on the basis of laboratory confirmation or linkage to a laboratory-confirmed case. Of these, 112 were students, the majority of whom had been vaccinated (81%). Although outbreaks in vaccinated populations have been described before, risk factors for exposure and susceptibility, and dose-dependent vaccine effectiveness in a student population of this nature are relatively unknown
Single-Top-Quark Production via W-Gluon Fusion at Next-to-Leading Order
Single-top-quark production via W-gluon fusion at hadron colliders provides
an opportunity to directly probe the charged-current interaction of the top
quark. We calculate the next-to-leading-order corrections to this process at
the Fermilab Tevatron, the CERN Large Hadron Collider, and DESY HERA. Using a
b-quark distribution function to sum collinear logarithms, we show that there
are two independent corrections, of order 1/[ln(m_t^2/m_b^2)] and alpha_s. This
observation is generic to processes involving a perturbatively derived
heavy-quark distribution function at an energy scale large compared with the
heavy-quark mass.Comment: 19 pages, 9 figures, small update to Phys. Rev. D versio
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