184 research outputs found
Resurrecting light stops after the 125 GeV Higgs in the baryon number violating CMSSM
In order to accommodate the observed Higgs boson mass in the CMSSM, the stops
must either be very heavy or the mixing in the stop sector must be very large.
Lower stop masses, possibly more accessible at the LHC, still give the correct
Higgs mass only if the trilinear stop mixing parameter is in the
multi-TeV range. Recently it has been shown that such large stop mixing leads
to an unstable electroweak vacuum which spontaneously breaks charge or colour.
In this work we therefore go beyond the CMSSM and investigate the effects of
including baryon number violating operators on the stop and Higgs sectors. We find that for light stop masses as low as 220 GeV are consistent
with the observed Higgs mass as well as flavour constraints while allowing for
a stable vacuum. The light stop in this scenario is often the lightest
supersymmetric particle. We furthermore discuss the importance of the one-loop
corrections involving R-parity violating couplings for a valid prediction of
the light stop masses.Comment: 26 pages, 9 figures; v2: slightly extended discussion about bounds
from flavour observables; matches published versio
Nielsen-Olesen vortex in varying-alpha theories
We consider soliton solutions to Bekenstein's theory, for which the fine
structure constant is allowed to vary due to the
presence of a dielectric field pervading the vacuum. More specifically we
investigate the effects of a varying upon a complex scalar field with
a U(1) electromagnetic gauge symmetry subject to spontaneous symmetry breaking.
We find vortex solutions to this theory, similar to the Nielsen-Olesen vortex.
Near the vortex core the electric charge is typically much larger than far away
from the string, lending these strings a superconducting flavour. In general
the dielectric field coats the usual local string with a global string
envelope. We discuss the cosmological implications of networks of such strings,
with particular emphasis on their ability to generate inhomogeneous
recombination scenarios. We also consider the possibility of the dielectric
being a charged free field. Even though the vacuum of such a field is trivial,
we find that the dielectric arranges itself in the shape of a local string,
with a quantized magnetic flux at the core -- presumably borrowing these
topological features from the underlying Nielsen-Olesen vortex.Comment: 7 pages, 1 figur
Fermion Masses and Mixing in Four and More Dimensions
We give an overview of recent progress in the study of fermion mass and
flavor mixing phenomena. Mass matrix ansatze are considered within the SM and
SUSY GUTs where some predictive frameworks based on SU(5) and SO(10) are
reviewed. We describe a variety of schemes to construct quark mass matrices in
extra dimensions focusing on four major classes: models with the SM residing on
3-brane, models with universal extra dimensions, models with split fermions and
models with warped extra dimensions. We outline how realistic patterns of quark
mass matrices could be derived from orbifold models in heterotic superstring
theory. Finally, we address the fermion mass problem in intersecting D-branes
scenarios, and present models with D6-branes able to give a good quantitatively
description of quark masses and mixing. The role of flavor/CP violation problem
as a probe of new physics is emphasized.Comment: a review based on seminars presented by S.K. in different places, 34
pages, late
Cardiac troponin T is elevated and increases longitudinally in ALS patients.
Objective: To test whether high-sensitivity cardiac troponin T (hs-cTnT) could act as a diagnostic or prognostic biomarker in ALS, comparing hs-cTnT to neurofilament light (NfL). Methods: We performed a case-control study, including 150 ALS patients, 28 ALS mimics, and 108 healthy controls, and a follow-up study of the ALS patients, during 2014-2020 in Stockholm, Sweden. We compared concentrations of hs-cTnT in plasma and NfL in the cerebrospinal fluid between cases and controls. To evaluate the diagnostic performance, we calculated the area under the curve (AUC). Hazard ratios (HRs) were estimated from Cox models to assess associations between hs-cTnT and NfL at ALS diagnosis and risk of death. The longitudinal analysis measured changes of hs-cTnT and NfL since ALS diagnosis. Results: We noted higher levels of hs-cTnT in ALS patients (median: 16.5 ng/L) than in ALS mimics (11 ng/L) and healthy controls (6 ng/L). Both hs-cTnT and NfL could distinguish ALS patients from ALS mimics, with higher AUC noted for NfL (AUC 0.88; 95%CI 0.79-0.97). Disease progression correlated weakly with hs-cTnT (Pearson's r = 0.18, p = 0.04) and moderately with NfL (Pearson's r = 0.41, p < 0.001). Shorter survival was associated with higher levels of NfL at diagnosis (HR 1.08, 95%CI 1.04-1.11), but not hs-cTnT. hs-cTnT increased (12.61 ng/L per year, 95%CI 7.14-18.06) whereas NfL decreased longitudinally since ALS diagnosis. Conclusions: NfL is a stronger diagnostic and prognostic biomarker than hs-cTnT for ALS. However, hs-cTnT might constitute a disease progression biomarker as it increases longitudinally. The underlying causes for this increase need to be investigated
WMAP Data and Recent Developments in Supersymmetric Dark Matter
A brief review is given of the recent developments in the analyses of
supersymmetric dark matter. Chief among these is the very accurate
determination of the amount of cold dark matter in the universe from analyses
using WMAP data. The implications of this data for the mSUGRA parameter space
are analyzed. It is shown that the data admits solutions on the hyperbolic
branch (HB) of the radiative breaking of the electroweak symmetry. A part of
the hyperbolic branch lies in the so called inversion region where the LSP
neutralino becomes essentially a pure Higgsino and degenerate with
the next to the lightest neutralino and the light chargino
. Thus some of the conventional signals for the observation of
supersymmetry at colliders (e.g., the missing energy signals) do not operate in
this region. On the other hand the inversion region contains a high degree of
degeneracy of , , leading to coannihilations
which allow for the satisfaction of the WMAP relic density constraints deep on
the hyperbolic branch. Further, an analysis of the neutralino-proton cross
sections in this region reveals that this region can still be accessible to
dark matter experiments in the future. Constraints from and from
are discussed. Future prospects are also discussed.Comment: 15 pages Latex. Invited talk at the IV International Conference on
Non-accelerator New Physics (NANP'03), Dubna, Russia, June 23-28, 200
Yukawa unification in SO(10) with light sparticle spectrum
We investigate supersymmetric SO(10) GUT model with \mu<0. The requirements
of top-bottom-tau Yukawa unification, correct radiative electroweak symmetry
breaking and agreement with the present experimental data may be met when the
soft masses of scalars and gauginos are non-universal. We show how appropriate
non-universalities can easily be obtained in the SO(10) GUT broken to the
Standard Model. We discuss how values of BR(b-->s \gamma) and (g-2)_\mu
simultaneously in a good agreement with the experimental data can be achieved
in SO(10) model with \mu<0. In the region of the parameter space preferred by
our analysis there are two main mechanisms leading to the LSP relic abundance
consistent with the WMAP results. One is the co-annihilation with the stau and
the second is the resonant annihilation via exchange of the Z boson or the
light Higgs scalar. A very interesting feature of SO(10) models with negative
\mu is that they predict relatively light sparticle spectra. Even the heaviest
superpartners may easily have masses below 1.5 TeV in contrast to multi-TeV
particles typical for models with positive \mu.Comment: 23 pages, 5 figure
Constraints on the Variations of the Fundamental Couplings
We reconsider several current bounds on the variation of the fine-structure
constant in models where all gauge and Yukawa couplings vary in an
interdependent manner, as would be expected in unified theories. In particular,
we re-examine the bounds established by the Oklo reactor from the resonant
neutron capture cross-section of 149Sm. By imposing variations in \Lambda_{QCD}
and the quark masses, as dictated by unified theories, the corresponding bound
on the variation of the fine-structure constant can be improved by about 2
orders of magnitude in such theories. In addition, we consider possible bounds
on variations due to their effect on long lived \alpha- and \beta-decay
isotopes, particularly 147Sm and 187Re. We obtain a strong constraint on \Delta
\alpha / \alpha, comparable to that of Oklo but extending to a higher redshift
corresponding to the age of the solar system, from the radioactive life-time of
187Re derived from meteoritic studies. We also analyze the astrophysical
consequences of perturbing the decay Q values on bound state \beta-decays
operating in the s-process.Comment: 25 pages, latex, 5 eps figure
Electroweak Supersymmetry around the Electroweak Scale
Inspired by the phenomenological constraints, LHC supersymmetry and Higgs
searches, dark matter search as well as string model building, we propose the
electroweak supersymmetry around the electroweak scale: the squarks and/or
gluinos are around a few TeV while the sleptons, sneutrinos, bino and winos are
within one TeV. The Higgsinos can be either heavy or light. We consider bino as
the dominant component of dark matter candidate, and the observed dark matter
relic density is achieved via the neutralino-stau coannihilations. Considering
the Generalized Minimal Supergravity (GmSUGRA), we show explicitly that the
electroweak supersymmetry can be realized, and the gauge coupling unification
can be preserved. With two Scenarios, we study the viable parameter spaces that
satisfy all the current phenomenological constraints, and we present the
concrete benchmark points. Furthermore, we comment on the fine-tuning problem
and LHC searches.Comment: RevTex4, 28 pages, 8 figures, 8 tables, version to appear in EPJ
General Gauge and Anomaly Mediated Supersymmetry Breaking in Grand Unified Theories with Vector-Like Particles
In Grand Unified Theories (GUTs) from orbifold and various string
constructions the generic vector-like particles do not need to form complete
SU(5) or SO(10) representations. To realize them concretely, we present
orbifold SU(5) models, orbifold SO(10) models where the gauge symmetry can be
broken down to flipped SU(5) X U(1)_X or Pati-Salam SU(4)_C X SU(2)_L X SU(2)_R
gauge symmetries, and F-theory SU(5) models. Interestingly, these vector-like
particles can be at the TeV-scale so that the lightest CP-even Higgs boson mass
can be lifted, or play the messenger fields in the Gauge Mediated Supersymmetry
Breaking (GMSB). Considering GMSB, ultraviolet insensitive Anomaly Mediated
Supersymmetry Breaking (AMSB), and the deflected AMSB, we study the general
gaugino mass relations and their indices, which are valid from the GUT scale to
the electroweak scale at one loop, in the SU(5) models, the flipped SU(5) X
U(1)_X models, and the Pati-Salam SU(4)_C X SU(2)_L X SU(2)_R models. In the
deflected AMSB, we also define the new indices for the gaugino mass relations,
and calculate them as well. Using these gaugino mass relations and their
indices, we may probe the messenger fields at intermediate scale in the GMSB
and deflected AMSB, determine the supersymmetry breaking mediation mechanisms,
and distinguish the four-dimensional GUTs, orbifold GUTs, and F-theory GUTs.Comment: RevTex4, 45 pages, 15 tables, version to appear in JHE
Dynamic Interpretation of Hedgehog Signaling in the Drosophila Wing Disc
Morphogens are classically defined as molecules that control patterning by acting at a distance to regulate gene expression in a concentration-dependent manner. In the Drosophila wing imaginal disc, secreted Hedgehog (Hh) forms an extracellular gradient that organizes patterning along the anterior–posterior axis and specifies at least three different domains of gene expression. Although the prevailing view is that Hh functions in the Drosophila wing disc as a classical morphogen, a direct correspondence between the borders of these patterns and Hh concentration thresholds has not been demonstrated. Here, we provide evidence that the interpretation of Hh signaling depends on the history of exposure to Hh and propose that a single concentration threshold is sufficient to support multiple outputs. Using mathematical modeling, we predict that at steady state, only two domains can be defined in response to Hh, suggesting that the boundaries of two or more gene expression patterns cannot be specified by a static Hh gradient. Computer simulations suggest that a spatial “overshoot” of the Hh gradient occurs, i.e., a transient state in which the Hh profile is expanded compared to the Hh steady-state gradient. Through a temporal examination of Hh target gene expression, we observe that the patterns initially expand anteriorly and then refine, providing in vivo evidence for the overshoot. The Hh gene network architecture suggests this overshoot results from the Hh-dependent up-regulation of the receptor, Patched (Ptc). In fact, when the network structure was altered such that the ptc gene is no longer up-regulated in response to Hh-signaling activation, we found that the patterns of gene expression, which have distinct borders in wild-type discs, now overlap. Our results support a model in which Hh gradient dynamics, resulting from Ptc up-regulation, play an instructional role in the establishment of patterns of gene expression
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