60,825 research outputs found
No-scale supergravity confronts LEP diphoton events
We examine the possibility that some anomalous acoplanar diphoton events
observed at LEP may be consistent with the predictions of our previously
proposed one-parameter no-scale supergravity model with a light gravitino, via
the process e^+e^- -> chi chi -> gamma gamma+E_miss. We find that one such
event may indeed be consistent with the model predictions for m_chi \approx
(60-70) GeV. This region of parameter space is also consistent with the
selectron and chargino interpretations of the CDF ee gamma gamma + E_T,miss
event.Comment: 9 pages, LaTeX, 4 figures (included). Updated to include full LEP161
dat
The SuperWorlds of SU(5) and SU(5)xU(1): A Critical Assessment and Overview
We present an overview of the simplest supergravity models which enforce
radiative breaking of the electroweak symmetry, namely the minimal
supergravity model and the class of string-inspired/derived supergravity models
based on the flipped structure supplemented by a minimal set
of additional matter representations such that unification occurs at the string
scale (\sim10^{18}\GeV). These models can be fully parametrized in terms of
the top-quark mass, the ratio , and three supersymmetry
breaking parameters (). The latter are chosen in the minimal
model such that the stringent constraints from proton decay and
cosmology are satisfied. In the flipped case we consider two
string-inspired supersymmetry breaking scenaria: no-scale
supergravity and a dilaton-induced supersymmetry breaking scenario. Both imply
universal soft supersymmetry breaking parameters: and
m_0=\coeff{1}{\sqrt{3}}m_{1/2}, A=-m_{1/2} respectively. We present a
comparative study of the sparticle and Higgs spectra of both flipped
models and the minimal model and conclude that all can be partially
probed at the Tevatron and LEPII (and the flipped models at HERA too). In both
flipped cases there is a more constrained version which allows to
determine in terms of and which leads to much
sharper and readily accessible experimental predictions. We also discuss the
prospects for indirect experimental detection: a non-trivial fraction of the
parameter space of the flipped models is in conflict with the present
experimental allowed range for the rare decay mode, and the
one-loop electroweak radiative corrections imply the 90\% CL upper boundComment: CERN-TH.6934/93, CTP-TAMU-34/93, LaTeX, 58 pages, 20 embedded
figures. Complete ps file (~12000 blocks, 5.24MB) available via anonymous ftp
from site tamsun.tamu.edu in directory incoming, filename: CTP-TAMU-34-93.p
SU(5)xU(1): a string paradigm of a TOE and its experimental consequences
We present a string-inspired/derived supergravity model based on the flipped
structure supplemented by a minimal set of additional matter
representations such that unification occurs at the string scale
(\sim10^{18}\GeV). This model is complemented by two string supersymmetry
breaking scenaria: the no-scale supergravity model and a
dilaton-induced supersymmetry breaking scenario. Both imply universal soft
supersymmetry breaking parameters: and
m_0=\coeff{1}{\sqrt{3}}m_{1/2}, A=-m_{1/2} respectively. In either case the
models depend on only three parameters: , , and .
We present a comparative study of the sparticle and Higgs spectra of both
models and conclude that even though both can be partially probed at the
Tevatron, LEPII, and HERA, a larger fraction of the parameter space of the
no-scale model is actually accessible. In both cases there is a more
constrained version which allows to determine in terms of
. In the strict no-scale case we find that the value of
determines the sign of (\mu>0:\,m_t\lsim135\GeV,
\mu<0:\,m_t\gsim140\GeV) and whether the lightest Higgs boson mass is above
or below 100\GeV. In the more constrained version of the dilaton scenario,
and m_t\lsim155\GeV, 61\GeV\lsim m_h\lsim91\GeV
follow. Thus, continuing Tevatron top-quark searches and LEPI,II Higgs searches
could probe this restricted scenario completely.Comment: CERN-TH.6926/93, CTP-TAMU-33/93, LaTeX, 33 pages, 11 embedded
figures. Significant numerical correction to the dilaton scenario. Complete
ps file (7943 blocks,3.33MB) available via anonymous ftp from site
tamsun.tamu.edu in directory incoming, filename: CTP-TAMU-33-93.p
Boron determination in steels by Inductively-Coupled Plasma spectometry (ICP)
The sample is treated with 5N H2SO4 followed by concentrated HNO3 and the diluted mixture is filtered. Soluble B is determined in the filtrate by Inductively-Coupled Plasma (ICP) spectrometry after addition HCl and extraction of Fe with ethyl-ether. The residue is fused with Na2CO3 and, after treatment with HCl, the insoluble B is determined by ICP spectrometry as before. The method permits determination of ppm amounts of B in steel
Electromagnetic quasinormal modes of five-dimensional topological black holes
We calculate exactly the QNF of the vector type and scalar type
electromagnetic fields propagating on a family of five-dimensional topological
black holes. To get a discrete spectrum of quasinormal frequencies for the
scalar type electromagnetic field we find that it is necessary to change the
boundary condition usually imposed at the asymptotic region. Furthermore for
the vector type electromagnetic field we impose the usual boundary condition at
the asymptotic region and we discuss the existence of unstable quasinormal
modes in the five-dimensional topological black holes.Comment: 16 pages. Already published in Revista Mexicana de Fisic
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