361 research outputs found
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
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.
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
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
Exact Calculation of , \
We present an exact calculation of the Wilson coefficients
associated with the dipole moment operators. We also give an estimate of the
branching ratio for . We find that higher dimensional
effects are under control within for .Comment: 12 pages (plain TeX), 2 postscript figures available upon request.
UM-TH-93-20 , IP-ASTP-29-9
Calculation of a Class of Three-Loop Vacuum Diagrams with Two Different Mass Values
We calculate analytically a class of three-loop vacuum diagrams with two
different mass values, one of which is one-third as large as the other, using
the method of Chetyrkin, Misiak, and M\"{u}nz in the dimensional regularization
scheme. All pole terms in \epsilon=4-D (D being the space-time dimensions in a
dimensional regularization scheme) plus finite terms containing the logarithm
of mass are kept in our calculation of each diagram. It is shown that
three-loop effective potential calculated using three-loop integrals obtained
in this paper agrees, in the large-N limit, with the overlap part of
leading-order (in the large-N limit) calculation of Coleman, Jackiw, and
Politzer [Phys. Rev. D {\bf 10}, 2491 (1974)].Comment: RevTex, 15 pages, 4 postscript figures, minor corrections in K(c),
Appendix B removed, typos corrected, acknowledgements change
ZFITTER: a semi-analytical program for fermion pair production in e+e- annihilation, from version 6.21 to version 6.42
ZFITTER is a Fortran program for the calculation of fermion pair production
and radiative corrections at high energy e+e- colliders; it is also suitable
for other applications where electroweak radiative corrections appear. ZFITTER
is based on a semi-analytical approach to the calculation of radiative
corrections in the Standard Model. We present a summary of new features of the
ZFITTER program version 6.42 compared to version 6.21. The most important
additions are: (i) some higher-order QED corrections to fermion pair
production, (ii) electroweak one-loop corrections to atomic parity violation,
(iii) electroweak one-loop corrections to nu-e nu-e-bar production, (iv)
electroweak two-loop corrections to the W boson mass and the effective weak
mixing angle.Comment: 60 pages, latex, 3 table
Do Two Symmetry Breaking Transitions in Photosynthetic Light Harvesting Complexes Form One, Two or More Kibble Zurek Model Topological Defects?
Kibble and Zurek proposed that rapid symmetry breaking transitions in the
hot, early universe could result in causally disconnected topological defects
such as cosmic strings. This type of first order transition has analogues in
certain second order transitions present in condensed matter such as liquid
crystals, super fluids, and charge density waves in terms of flux tubes or
vortices. Recently, we discovered that Rhodopseudomonas acidophilus
photosynthetic light harvesting complex might have different types of coherent
ground and excited states, suggesting that there are two different symmetry
breaking transitions. The B 850 ground states comprise eight identical rings
each containing 18 bacteriochlorophyll components, and each ring has undergone
a Bose Einstein phase transition to a charge density wave that lowers the
energy. The excited state coherence results from polariton formation from the
non-crossing of bosons, here an extension of exciton theory. The result is
short-lived quasi-particles with very low mass that can form an unusual BEC. We
suggest the oriented, circular B 850 and enclosed singlet B 875 compounds
create a new cavity structure with some attributes of a nano pillar. Since both
the ground and excited states should contain solitons, we envisage three fast
light pulse experiments could be able to map both the Kibble Zurek Model phase
transitions and energy transfers as a function of light intensity and time in
this complex at room temperature
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