3,740 research outputs found
Identifying Unconventional E Models at Colliders
Recently it was shown that, in the framework of superstring inspired \E
models, the presence of generation dependent discrete symmetries allows us to
construct a phenomenologically viable class of models in which the three
generations of fermions do not have the same embedding within the fundamental
{\bf 27} dimensional representation of E. In this scenario, these different
embeddings of the conventional fermions imply that the left-handed charged
leptons and the right-handed -type quarks are coupled in a non--universal
way to the new neutral gauge bosons present in these models. It
was also shown that a unique signature for this scenario, would be a deviation
from unity for the ratio of cross sections for the production of two different
lepton species in annihilation. However, several different scenarios
are possible, depending on the particular assignment chosen for ,
and and for the right-handed -type quarks, as well as on the type
of boson. Such scenarios can not be disentangled from one another by
means of cross section measurements alone. In this paper we examine the
possibility of identifying the pattern of embeddings through measurements of
polarized and unpolarized asymmetries for fermion pair-production at the 500
GeV Next Linear Collider (NLC). We show that it will be possible to
identify the different patterns of unconventional assignments for the
left-handed leptons and for the quark, for masses as large as
TeV.Comment: Plain Tex, 15 pages, + 9 figure available upon request
([email protected] or [email protected]), UM-TH 93--1
Nonlinear household earnings dynamics, self-insurance, and welfare
Earnings dynamics are much richer than typically assumed in macro models with heterogeneous agents. This holds for individual-pre-tax and household-post-tax earnings and across administrative and survey data. We estimate two alternative processes for household after-tax earnings and study their implications using a standard life-cycle model. Both processes feature a persistent and a transitory component, but although the first one is the canonical linear process with stationary shocks, the second one has substantially richer earnings dynamics, allowing for age-dependence of moments, non-normality, and nonlinearity in previous earnings and age. Allowing for richer earnings dynamics implies a substantially better fit of the evolution of cross-sectional consumption inequality over the life cycle and of the individual-level degree of consumption insurance against persistent earnings shocks. The richer earnings process implies lower welfare costs of earnings risk
Signals of Unconventional E Models at Colliders
Generation dependent discrete symmetries often appear in models derived from
superstring theories. In particular, in the framework of E models the
presence of such symmetries is required in order to allow for the radiative
generation of naturally small neutrino masses. Recently it was shown that by
imposing suitable generation dependent discrete symmetries, a class of models
can be consistently constructed in which the three sets of known fermions in
each generation do not have the same assignments with respect to the {\bf 27}
representation of E. In this scenario, the different embedding in the gauge
group of the three generations implies in particular that the known charged
leptons couple in a non--universal way to the new neutral gauge bosons
present in these models. We exploit this fact to study the
signature of this class of models at present and future colliders. We
show that some signals of deviation from lepton universality as well as some
other discrepancies with the standard model predictions which have been
observed at the TRISTAN collider in the production rate of and ,
can be accounted for if the mass is not much heavier than 300 GeV. We
also study the discovery limits for lepton universality violation of this type
at LEP-2 and at the 500 GeV Next Linear Collider (NLC). We show that
models predicting unconventional assignments for the leptons will give an
unmistakable signature, when the mass is as heavy as GeV
(LEP-2) and TeV (NLC).Comment: Plain Tex, 20 pages. 4 PostScript figures (uses `epsf.tex'). Modified
file-format. No changes in the tex
Early mandibular canine-lateral incisor transposition: case report
Purpose. The main aim of the present study is to present a case of mandibular transposition between lateral incisor and
canine in a paediatric patient.
Materials and methods. A fixed multibracket orthodontic treatment was performed by means of a modified welded arch
as to correct the transposition and obtaining a class I functional and symmetrical occlusion, also thanks to the early diagnosis
of the eruption anomaly.
Results. Our case report shows that a satisfactory treatment of mandibular transpositions is obtained when detected at
an early stage of the tooth development.
Conclusions. The main treatment options to be taken into consideration in case of a mandibular transposition are two:
correcting the transposition or aligning it leaving the dental elements in their transposed order; in both cases, the followups
show a stable condition, maintained without relapses. Several factors, such as age of the patient, occlusion, aesthetics,
patient’s collaboration, periodontal support and duration of treatment have to be considered as to prevent potential damage
to dental elements and support appliances. The choice between the two treatment approaches for mandibular lateral
incisor/canine transpositions mainly depends on the time the anomaly is detected
Z', new fermions and flavor changing processes, constraints on E models from --> eee
We study a new class of flavor changing interactions, which can arise in
models based on extended gauge groups (rank 4) when new charged fermions are
present together with a new neutral gauge boson. We discuss the cases in which
the flavor changing couplings in the new neutral current coupled to the
are theoretically expected to be large, implying that the observed
suppression of neutral flavor changing transitions must be provided by heavy
masses together with small - mixing angles.
Concentrating on E models, we show how the tight experimental limit on implies serious constraints on the mass and mixing
angle. We conclude that if the value of the flavor changing parameters is
assumed to lie in a theoretically natural range, in most cases the presence of
a much lighter than 1 TeV is unlikely.Comment: plain tex, 22 pages + 2 pages figures in PostScript (appended after
`\bye'), UM-TH 92-1
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