1,278 research outputs found
On character generators for simple Lie algebras
We study character generating functions (character generators) of simple Lie
algebras. The expression due to Patera and Sharp, derived from the Weyl
character formula, is first reviewed. A new general formula is then found. It
makes clear the distinct roles of ``outside'' and ``inside'' elements of the
integrity basis, and helps determine their quadratic incompatibilities. We
review, analyze and extend the results obtained by Gaskell using the Demazure
character formulas. We find that the fundamental generalized-poset graphs
underlying the character generators can be deduced from such calculations.
These graphs, introduced by Baclawski and Towber, can be simplified for the
purposes of constructing the character generator. The generating functions can
be written easily using the simplified versions, and associated Demazure
expressions. The rank-two algebras are treated in detail, but we believe our
results are indicative of those for general simple Lie algebras.Comment: 50 pages, 11 figure
The Ni(n,) cross section measured with DANCE
The neutron capture cross section of the s-process branch nucleus Ni
affects the abundances of other nuclei in its region, especially Cu and
Zn. In order to determine the energy dependent neutron capture cross
section in the astrophysical energy region, an experiment at the Los Alamos
National Laboratory has been performed using the calorimetric 4 BaF
array DANCE. The (n,) cross section of Ni has been determined
relative to the well known Au standard with uncertainties below 15%.
Various Ni resonances have been identified based on the Q-value.
Furthermore, the s-process sensitivity of the new values was analyzed with the
new network calculation tool NETZ.Comment: 11 pages, 13 page
Generating-function method for tensor products
This is the first of two articles devoted to a exposition of the
generating-function method for computing fusion rules in affine Lie algebras.
The present paper is entirely devoted to the study of the tensor-product
(infinite-level) limit of fusions rules.
We start by reviewing Sharp's character method. An alternative approach to
the construction of tensor-product generating functions is then presented which
overcomes most of the technical difficulties associated with the character
method. It is based on the reformulation of the problem of calculating tensor
products in terms of the solution of a set of linear and homogeneous
Diophantine equations whose elementary solutions represent ``elementary
couplings''. Grobner bases provide a tool for generating the complete set of
relations between elementary couplings and, most importantly, as an algorithm
for specifying a complete, compatible set of ``forbidden couplings''.Comment: Harvmac (b mode : 39 p) and Pictex; this is a substantially reduced
version of hep-th/9811113 (with new title); to appear in J. Math. Phy
Electric Dipole moments of charged leptons and lepton flavor violating interactions in the general two Higgs Doublet model
We calculate the electric dipole moment of electron using the experimental
result of muon electric dipole moment and upper limit of the BR(\mu -->
e\gamma) in the framework of the general two Higgs doublet model. Our
prediction is 10^{-32} e-cm, which lies in the experimental current limits.
Further, we obtain constraints for the Yukawa couplings \bar{\xi}^{D}_{N,\tau
e} and \bar{\xi}^{D}_{N,\tau\mu}. Finally we present an expression which
connects the BR(\tau\to \mu\gamma) and the electric dipole moment of
\tau-lepton and study the relation between these physical quantities.Comment: 8 pages, 4 Figures (required epsf sty
The radiative lepton flavor violating decays in the split fermion scenario in the two Higgs doublet model
We study the branching ratios of the lepton flavor violating processes \mu ->
e \gamma, \tau -> e \gamma and \tau -> \mu\gamma in the split fermion scenario,
in the framework of the two Higgs doublet model. We observe that the branching
ratios are relatively more sensitive to the compactification scale and the
Gaussian widths of the leptons in the extra dimensions, for two extra
dimensions and especially for the \tau -> \mu \gamma decay.Comment: 19 pages, 7 Figure
Searching for Anomalous Weak Couplings of Heavy Flavors at the SLC and LEP
The existence of anomalous electric() and/or
magnetic() dipole moment couplings between the heavy flavor fermions
() and the boson can cause significant shifts in the values of
several electroweak observables currently being probed at both the SLC and LEP.
Using the good agreement between existing data and the predictions of the
Standard Model we obtain strict bounds on the possible strength of these new
interactions for all of the heavy flavors. The decay ,
however, provides some possible hint of new physics. The corresponding
anomalous couplings of 's to photons is briefly examined.Comment: 21 pages, 14 figs(available on request), LaTex, SLAC-PUB-667
Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains
The influence of the combined effects of substrate-induced strain, finite
size and electron irradiation-induced defects have been studied on individual
micron-sized domains of the organic charge transfer compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent
conductivity and current-voltage measurements. The individual domains have been
isolated by focused ion beam etching and electrically contacted by focused ion
and electron beam induced deposition of metallic contacts. The
temperature-dependent conductivity follows a variable range hopping behavior
which shows a crossover of the exponent as the Peierls transition is
approached. The low temperature behavior is analyzed within the segmented rod
model of Fogler, Teber and Shklowskii, as originally developed for a
charge-ordered quasi one-dimensional electron crystal. The results are compared
with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin
films of the two-domain type
Fermion contribution to the static quantities of arbitrarily charged vector bosons
We present an analysis of the one-loop contribution from left- and
right-handed fermions to the static electromagnetic properties of an
arbitrarily charged no self-conjugate vector boson . Particular emphasis is
given to the case of a no self-conjugate neutral boson . Regardless the
electric charge of the boson, a fermionic loop can induce the two CP-even
form factors but only one CP-odd. As a result the corresponding electric dipole
moment is directly proportional to the magnetic quadrupole moment. The CP-odd
form factor might be severely suppressed since it requires the presence of both
left- and right-handed fermions. The behavior of the form factors is analyzed
for several scenarios of the fermion masses in the context of the decoupling
theorem.Comment: 12 pages, 3 figures, submitted to Journal of Physics
Single top production at the LHC as a probe of R parity violation
We investigate the potential of the LHC to probe the R parity violating
couplings involving the third generation by considering single top production.
This study is based on particle level event generation for both signal and
background, interfaced to a simplified simulation of the ATLAS detector.Comment: 11 pages, 5 figures, 5 tables (LaTeX, style revtex), few references
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W ANOMALOUS MOMENTS AND THE POLARIZATION ASYMMETRY ZERO IN gamma e --> W nu
We show from general principles that there must be a center of mass energy,
, where the polarization asymmetry for circularly-polarized photon and
electron beams vanishes. In the case of the Standard Model, the crossing point
where the asymmetry changes sign occurs in Born approximation at GeV. We demonstrate the sensitivity
of the position of the polarization asymmetry zero to modifications of the SM
trilinear coupling. Given reasonable assumptions for the
luminosity and energy range for the Next Linear Collider(NLC) with a
backscattered laser beam, we show that the zero point, , of the
polarization asymmetry may be determined with sufficient precision to constrain
the anomalous couplings of the to better than the 1\% level at CL.
In addition to the fact that only a limited range of energy is required, the
polarization asymmetry measurements have the important advantage that many of
the systematic errors cancel in taking cross section ratios. The position of
the zero thus provides an additional weapon in the arsenal used to probe
anomalous trilinear gauge couplings.Comment: 21 pages, uuencoded postscript file. For hard copy, send e-mail to
[email protected]
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