582 research outputs found
Finite Higgs mass without Supersymmetry
We identify a class of chiral models where the one-loop effective potential
for Higgs scalar fields is finite without any requirement of supersymmetry. It
corresponds to the case where the Higgs fields are identified with the
components of a gauge field along compactified extra dimensions. We present a
six dimensional model with gauge group U(3)xU(3) and quarks and leptons
accomodated in fundamental and bi-fundamental representations. The model can be
embedded in a D-brane configuration of type I string theory and, upon
compactification on a T^2/Z_2 orbifold, it gives rise to the standard model
with two Higgs doublets.Comment: 28 pages, 4 figures, uses axodraw. Some typos corrected and
references rearrange
Localized anomalies in orbifold gauge theories
We apply the path-integral formalism to compute the anomalies in general
orbifold gauge theories (including possible non-trivial Scherk-Schwarz boundary
conditions) where a gauge group G is broken down to subgroups H_f at the fixed
points y=y_f. Bulk and localized anomalies, proportional to \delta(y-y_f), do
generically appear from matter propagating in the bulk. The anomaly zero-mode
that survives in the four-dimensional effective theory should be canceled by
localized fermions (except possibly for mixed U(1) anomalies). We examine in
detail the possibility of canceling localized anomalies by the Green-Schwarz
mechanism involving two- and four-forms in the bulk. The four-form can only
cancel anomalies which do not survive in the 4D effective theory: they are
called globally vanishing anomalies. The two-form may cancel a specific class
of mixed U(1) anomalies. Only if these anomalies are present in the 4D theory
this mechanism spontaneously breaks the U(1) symmetry. The examples of five and
six-dimensional Z_N orbifolds are considered in great detail. In five
dimensions the Green-Schwarz four-form has no physical degrees of freedom and
is equivalent to canceling anomalies by a Chern-Simons term. In all other
cases, the Green-Schwarz forms have some physical degrees of freedom and leave
some non-renormalizable interactions in the low energy effective theory. In
general, localized anomaly cancellation imposes strong constraints on model
building.Comment: 30 pages, 4 figures. v2: reference adde
Supersymmetry and Electroweak breaking from extra dimensions at the TeV-scale
We analyze some features of the role that extra dimensions, of radius in
the TeV range, can play in the soft breaking of supersymmetry and the
spontaneous breaking of electroweak symmetry. We use a minimal model where the
gauge and Higgs sector of the MSSM are living in the bulk of five dimensions
and the chiral multiplets in a four-dimensional boundary. Supersymmetry is
broken in the bulk by the Scherk-Schwarz mechanism and transmitted to the
boundary by radiative corrections. The particle spectrum is completely
predicted as a function of a unique -charge. The massless sector corresponds
to the pure Standard Model and electroweak symmetry is radiatively broken with
a light Higgs weighing \simlt 110 GeV. The -problem is solved and
Higgsinos, gauginos and heavy Higgses acquire masses . Chiral
sfermions acquire radiative squared-masses . The effective
potential is explicitly computed in the bulk of extra dimensions and some
cosmological consequences can be immediately drawn from it. Gauge coupling
running and unification is studied in the presence of Scherk-Schwarz
supersymmetry breaking. The unification is similar to that in the
supersymmetric theory.Comment: 27 pages, Latex, 7 figures. Minor change
Supersymmetry breaking on orbifolds from Wilson lines
We consider five dimensional theories compactified on the orbifold S^1/Z_2
and prove that spontaneous local supersymmetry breaking by Wilson lines and by
the Scherk-Schwarz mechanism are equivalent. Wilson breaking is triggered by
the SU(2)_R symmetry which is gauged in off-shell N=2 supergravity by auxiliary
fields. The super-Higgs mechanism disposes of the would-be Goldstinos which are
absorbed by the gravitinos to become massive. The breaking survives in the flat
limit, where we decouple all gravitational interactions, and the theory becomes
softly broken global supersymmetry.Comment: 9 pages, some comments in the discussion of the super-Higgs effect
and some references adde
The Impact of Kaluza-Klein Excited W Boson on the Single Top at LHC and Comparison with other Models
We study the s-channel single top quark production at the LHC in the context
of extra dimension theories, including the Kaluza-Klein (KK) decomposition. It
is shown that the presence of the first KK excitation of gauge boson can
reduce the total cross section of s-channel single top production considerably
if () for () in
proton-proton collisions. Then the results will be compared with the impacts of
other beyond Standard Model (SM) theories on the cross section of single top
s-channel. The possibility of distinguishing different models via their effects
on the production cross section of the s-channel is discussed.Comment: 23 pages,6 figure
An Introduction to Extra Dimensions
Models that involve extra dimensions have introduced completely new ways of
looking up on old problems in theoretical physics. The aim of the present notes
is to provide a brief introduction to the many uses that extra dimensions have
found over the last few years, mainly following an effective field theory point
of view. Most parts of the discussion are devoted to models with flat extra
dimensions, covering both theoretical and phenomenological aspects. We also
discuss some of the new ideas for model building where extra dimensions may
play a role, including symmetry breaking by diverse new and old mechanisms.
Some interesting applications of these ideas are discussed over the notes,
including models for neutrino masses and proton stability. The last part of
this review addresses some aspects of warped extra dimensions, and graviton
localization.Comment: 39 pages. Two figures. Comments and references added. Lectures given
at the XI Mexican School of Particles and Fields. Xalapa, Mexico, August
1-13, 200
Gapped continuum Kaluza-Klein spectrum
We consider a warped ve-dimensional model with an ultraviolet (UV) brane
and, on top of the Standard Model isolated modes, continua of KK modes with different
mass gaps for all particles: gauge bosons, fermions, graviton, radion and Higgs boson. The
model can be considered as a modelization in ve dimensions of gapped unparticles. The
ve dimensional metric has a singularity, at a finite (infinite) value of the proper (conformal)
coordinate, which is admissible as it supports finite temperature in the form of a black
hole horizon. An infrared (IR) brane, with particular jumping conditions, is introduced
to trigger correct electroweak breaking. The gravitational metric is AdS5 near the UV
brane, to solve the hierarchy problem with a fundamental Planck scale, and linear, in
conformal coordinates, near the IR, as in the linear dilaton and ve-dimensional clockwork
models. The branes, and singularity, distances are fixed, à la Goldberger-Wise, by a bulk
scalar field with brane potentials explicitly breaking the conformal symmetry. The bosonic
continuum of KK modes with the smallest mass gap are those of gauge bosons, and so they
are the most likely produced at the LHC. Mass gaps of the continuum of KK fermions
do depend on their localization in the extra dimension. We have computed the spectral
functions, and arbitrary Green's functions, and shown how they can modify some Standard
Model processes.The work of EM is supported by the Spanish MINEICO under Grant FIS2017-85053-C2-1-P, by the Junta de Andalucía under Grant FQM-225, by
the Consejería de Conocimiento, Investigación y Universidad of the Junta de Andalucía and
European Regional Development Fund (ERDF) under Grant SOMM17/6105/UGR, and by
the Spanish Consolider Ingenio 2010 Programme CPAN under Grant CSD2007-00042. The
research of EM is also supported by the Ramón y Cajal Program of the Spanish MINEICO
under Grant RYC-2016-20678. The work of MQ is partly supported by Spanish MINEICO
(Grant FPA2017-88915-P), by the Catalan Government under Grant 2017SGR1069, and
by Severo Ochoa Excellence Program of MINEICO (Grant SEV-2016-0588)
Les Houches 2015: Physics at TeV colliders - new physics working group report
We present the activities of the 'New Physics' working group for the 'Physics
at TeV Colliders' workshop (Les Houches, France, 1-19 June, 2015). Our report
includes new physics studies connected with the Higgs boson and its properties,
direct search strategies, reinterpretation of the LHC results in the building
of viable models and new computational tool developments. Important signatures
for searches for natural new physics at the LHC and new assessments of the
interplay between direct dark matter searches and the LHC are also considered.Comment: Proceedings of the New Physics Working Group of the 2015 Les Houches
Workshop, Physics at TeV Colliders, Les Houches 1-19 June 2015. 197 page
Evaluation of Hungarian Wines for Resveratrol by Overpressured Layer Chromatography
A method, including solid phase extraction sample preparation, overpressured layer chromatographic separation and subsequent densitometric evaluation, was developed for measurement of total resveratrol (cis- and trans-isomers) content of wine. The amount of resveratrol was determined in wine samples from different winemaking regions of Hungary. The total resveratrol was high in Hungarian red wines (3.6–11 mg/L), and much lower in white ones (0.04–1.5 mg/L)
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