10 research outputs found
One-loop Higgs mass finiteness in supersymmetric Kaluza-Klein theories
We analyze the one-loop ultraviolet sensitivity of the Higgs mass in a
five-dimensional supersymmetric theory compactified on the orbifold S^1/Z_2,
with superpotential localized on a fixed-point brane. Four-dimensional
supersymmetry is broken by Scherk-Schwarz boundary conditions. Kaluza-Klein
interactions are regularized by means of a brane Gaussian distribution along
the extra dimension with length l_s\simeq\Lambda^{-1}_s, where \Lambda_s is the
cutoff of the five-dimensional theory. The coupling of the n-mode, with mass
M^{(n)}, acquires the n-dependent factor exp{-(M^{(n)}/\Lambda_s)^2/2}, which
makes it to decouple for M^{(n)}\gg \Lambda_s. The sensitivity of the Higgs
mass on \Lambda_s is strongly suppressed and quadratic divergences cancel by
supersymmetry. The one-loop correction to the Higgs mass is finite and equals,
for large values of \Lambda_s, the value obtained by the so-called
KK-regularization.Comment: 8 pages, 1 figure. The discussion on the distribution giving rise to
couplings suppressed by exp(-M/Lambda) is revised and the result is finite
and equals that of the Gaussian cas
Supersymmetry breaking with quasi-localized fields in orbifold field theories
We study the Scherk-Schwarz supersymmetry breaking in five-dimensional
orbifold theories with five-dimensional fields which are not strictly localized
on the boundaries (quasi-localized fields). We show that the Scherk-Schwarz
(SS) mechanism, besides the SS parameter \omega, depends upon new parameters,
e.g. supersymmetric five-dimensional odd mass terms, governing the level of
localization on the boundaries of the five-dimensional fields and study in
detail such a dependence. Taking into account radiative corrections, the value
of \omega is dynamically allowed to acquire any value in the range 0< \omega <
1/2.Comment: 13 pages, 3 figure
Radiative Scherk-Schwarz supersymmetry breaking
We analyze the Scherk-Schwarz (SS) supersymmetry breaking in brane-world five
dimensional theories compactified on the orbifold . The SS
breaking parameter is undetermined at the tree-level (no-scale supergravity)
and can be interpreted as the Hosotani vacuum expectation value corresponding
to the group in five dimensional N=2 (ungauged) supergravity. We show
that the SS breaking parameter is fixed at the loop level to either 0 or 1/2
depending on the matter content propagating in the bulk but in a rather
model-independent way. Supersymmetry breaking is therefore fixed through a
radiative Scherk-Schwarz mechanism. We also show that the two discrete values
of the SS parameter, as well as the supersymmetry breaking shift in the
spectrum of the bulk fields, are altered in the presence of a brane-localized
supersymmetry breaking arising from some hidden sector dynamics. The interplay
between the SS and the brane localized breaking is studied in detail.Comment: 16 pages, 2 figures, uses axodraw. References adde
Supersymmetry and Finite Radiative Electroweak Breaking from an Extra Dimension
A five dimensional N=1 supersymmetric theory compactified on the orbifold
is constructed. Gauge fields and singlets
propagate in the bulk (-states) while doublets are localized at an
orbifold fixed point brane (-states). Zero bulk modes and localized states
constitute the MSSM and massive modes are arranged into N=2 supermultiplets.
Superpotential interactions on the brane are of the type . Supersymmetry
is broken in the bulk by a Scherk-Schwarz mechanism using the global
-symmetry. A radiative finite electroweak breaking is triggered by the
top-quark/squark multiplet propagating in the bulk. The
compactification radius is fixed by the minimization conditions and
constrained to be 1/R \simlt 10-15 TeV. It is also constrained by precision
electroweak measurements to be 1/R \simgt 4 TeV. The pattern of
supersymmetric mass spectrum is well defined. In particular, the lightest
supersymmetric particle is the sneutrino and the next to lightest
supersymmetric particle the charged slepton, with a squared-mass difference
. The theory couplings, gauge and Yukawa, remain perturbative up to
scales given, at one-loop, by ER \simlt 30-40. Finally, LEP searches on
the MSSM Higgs sector imply an absolute lower bound on the SM-like Higgs mass,
around 145 GeV in the one-loop approximation.Comment: 19 pages, 6 figures, Latex2e, axodraw.sty. Some changes concerning
LEP Higgs searche
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
Scherk-Schwarz Supersymmetry Breaking with Radion Stabilization
We study the issue of radion stabilization within five-dimensional
supersymmetric theories compactified on the orbifold S^1/Z_2. We break
supersymmetry by the Scherk-Schwarz mechanism and explain its implementation in
the off-shell formulation of five dimensional supergravity in terms of the
tensor and linear compensator multiplets. We show that radion stabilization may
be achieved by radiative corrections in the presence of five-dimensional fields
which are quasi-localized on the boundaries through the presence of Z_2 odd
mass terms. For the mechanism to work the number of quasi-localized fields
should be greater than 2+N_V-N_h where N_V and N_h are the number of massless
gauge- and hypermultiplets in the bulk. The radion is stabilized in a
metastable Minkowski vacuum with a lifetime much larger than cosmological
time-scales. The radion mass is in the meV range making it interesting for
present and future measurements of deviations from the gravitational
inverse-square law in the submillimeter range.Comment: 16 pages, 4 figure
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
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