46 research outputs found
Effects of prenatal exposure to diclofenac sodium and saline on the optic nerve of 4- and 20-week-old male rats: A stereological and histological study
When Anomaly Mediation is UV Sensitive
Despite its successes---such as solving the supersymmetric flavor
problem---anomaly mediated supersymmetry breaking is untenable because of its
prediction of tachyonic sleptons. An appealing solution to this problem was
proposed by Pomarol and Rattazzi where a threshold controlled by a light field
deflects the anomaly mediated supersymmetry breaking trajectory, thus evading
tachyonic sleptons. In this paper we examine an alternate class of deflection
models where the non-supersymmetric threshold is accompanied by a heavy,
instead of light, singlet. The low energy form of this model is the so-called
extended anomaly mediation proposed by Nelson and Weiner, but with potential
for a much higher deflection threshold. The existence of this high deflection
threshold implies that the space of anomaly mediated supersymmetry breaking
deflecting models is larger than previously thought.Comment: 14 pages, 1 figure (version to appear in JHEP
Fine-tuning implications for complementary dark matter and LHC SUSY searches
The requirement that SUSY should solve the hierarchy problem without undue
fine-tuning imposes severe constraints on the new supersymmetric states. With
the MSSM spectrum and soft SUSY breaking originating from universal scalar and
gaugino masses at the Grand Unification scale, we show that the low-fine-tuned
regions fall into two classes that will require complementary collider and dark
matter searches to explore in the near future. The first class has relatively
light gluinos or squarks which should be found by the LHC in its first run. We
identify the multijet plus E_T^miss signal as the optimal channel and determine
the discovery potential in the first run. The second class has heavier gluinos
and squarks but the LSP has a significant Higgsino component and should be seen
by the next generation of direct dark matter detection experiments. The
combined information from the 7 TeV LHC run and the next generation of direct
detection experiments can test almost all of the CMSSM parameter space
consistent with dark matter and EW constraints, corresponding to a fine-tuning
not worse than 1:100. To cover the complete low-fine-tuned region by SUSY
searches at the LHC will require running at the full 14 TeV CM energy; in
addition it may be tested indirectly by Higgs searches covering the mass range
below 120 GeV.Comment: References added. Version accepted for publication in JHE
Phenomenological Implications of Deflected Mirage Mediation: Comparison with Mirage Mediation
We compare the collider phenomenology of mirage mediation and deflected
mirage mediation, which are two recently proposed "mixed" supersymmetry
breaking scenarios motivated from string compactifications. The scenarios
differ in that deflected mirage mediation includes contributions from gauge
mediation in addition to the contributions from gravity mediation and anomaly
mediation also present in mirage mediation. The threshold effects from gauge
mediation can drastically alter the low energy spectrum from that of pure
mirage mediation models, resulting in some cases in a squeezed gaugino spectrum
and a gluino that is much lighter than other colored superpartners. We provide
several benchmark deflected mirage mediation models and construct model lines
as a function of the gauge mediation contributions, and discuss their discovery
potential at the LHC.Comment: 29 pages, 9 figure
Determining the WIMP mass from a single direct detection experiment, a more detailed study
The energy spectrum of nuclear recoils in Weakly Interacting Massive Particle
(WIMP) direct detection experiments depends on the underlying WIMP mass. We
study how the accuracy with which the WIMP mass could be determined by a single
direct detection experiment depends on the detector configuration and the WIMP
properties. We investigate the effects of varying the underlying WIMP mass and
cross-section, the detector target nucleus, exposure, energy threshold and
maximum energy, the local circular speed and the background event rate and
spectrum. The number of events observed is directly proportional to both the
exposure and the cross-section, therefore these quantities have the greatest
bearing on the accuracy of the WIMP mass determination. The relative
capabilities of different detectors to determine the WIMP mass depend not only
on the WIMP and target masses, but also on their energy thresholds. We find
that the rapid decrease of the nuclear form factor with increasing momentum
transfer which occurs for heavy nuclei, means that heavy nuclei will not
necessarily be able to measure the mass of heavy WIMPs more accurately.
Uncertainty in the local circular speed and non-negligible background would
both lead to systematic errors in the WIMP mass determination. With a single
detector it will be difficult to disentangle a WIMP signal (and the WIMP mass)
from background if the background spectrum has a similar shape to the WIMP
spectrum (i.e. exponential background, or flat background and a heavy WIMP).Comment: 20 pages, 11 figures, version to appear in JCAP, minor changes to
presentatio
Mixed Mediation of Supersymmetry Breaking with Anomalous U(1) Gauge Symmetry
Models with anomalous U(1) gauge symmetry contain various superfields which
can have nonzero supersymmetry breaking auxiliary components providing the
origin of soft terms in the visible sector, e.g. the U(1) vector superfield,
the modulus or dilaton superfield implementing the Green-Schwarz anomaly
cancellation mechanism, U(1)-charged but standard model singlet matter
superfield required to cancel the Fayet-Iliopoulos term, and finally the
supergravity multiplet. We examine the relative strength between these
supersymmetry breaking components in a simple class of models, and find that
various different mixed mediations of supersymmetry breaking, involving the
modulus, gauge, anomaly and D-term mediations, can be realized depending upon
the characteristics of D-flat directions and how those D-flat directions are
stabilized with a vanishing cosmological constant. We identify two parameters
which represent such properties and thus characterize how the various
mediations are mixed. We also discuss the moduli stabilization and soft terms
in a variant of KKLT scenario, in which the visible sector K\"ahler modulus is
stabilized by the D-term potential of anomalous U(1) gauge symmetry.Comment: 30 pages, 5 figure
Many faces of low mass neutralino dark matter in the unconstrained MSSM, LHC data and new signals
If all strongly interacting sparticles (the squarks and the gluinos) in an
unconstrained minimal supersymmetric standard model (MSSM) are heavier than the
corresponding mass lower limits in the minimal supergravity (mSUGRA) model,
obtained by the current LHC experiments, then the existing data allow a variety
of electroweak (EW) sectors with light sparticles yielding dark matter (DM)
relic density allowed by the WMAP data. Some of the sparticles may lie just
above the existing lower bounds from LEP and lead to many novel DM producing
mechanisms not common in mSUGRA. This is illustrated by revisiting the above
squark-gluino mass limits obtained by the ATLAS Collaboration, with an
unconstrained EW sector with masses not correlated with the strong sector.
Using their selection criteria and the corresponding cross section limits, we
find at the generator level using Pythia, that the changes in the mass limits,
if any, are by at most 10-12% in most scenarios. In some cases, however, the
relaxation of the gluino mass limits are larger (). If a subset of
the strongly interacting sparticles in an unconstrained MSSM are within the
reach of the LHC, then signals sensitive to the EW sector may be obtained. This
is illustrated by simulating the \etslash, , and \etslash signals in i) the light stop scenario and ii) the light
stop-gluino scenario with various light EW sectors allowed by the WMAP data.
Some of the more general models may be realized with non-universal scalar and
gaugino masses.Comment: 27 pages, 1 figure, references added, minor changes in text, to
appear in JHE
The Hunt for New Physics at the Large Hadron Collider
The Large Hadron Collider presents an unprecedented opportunity to probe the
realm of new physics in the TeV region and shed light on some of the core
unresolved issues of particle physics. These include the nature of electroweak
symmetry breaking, the origin of mass, the possible constituent of cold dark
matter, new sources of CP violation needed to explain the baryon excess in the
universe, the possible existence of extra gauge groups and extra matter, and
importantly the path Nature chooses to resolve the hierarchy problem - is it
supersymmetry or extra dimensions. Many models of new physics beyond the
standard model contain a hidden sector which can be probed at the LHC.
Additionally, the LHC will be a top factory and accurate measurements of the
properties of the top and its rare decays will provide a window to new physics.
Further, the LHC could shed light on the origin of neutralino masses if the new
physics associated with their generation lies in the TeV region. Finally, the
LHC is also a laboratory to test the hypothesis of TeV scale strings and
D-brane models. An overview of these possibilities is presented in the spirit
that it will serve as a companion to the Technical Design Reports (TDRs) by the
particle detector groups ATLAS and CMS to facilitate the test of the new
theoretical ideas at the LHC. Which of these ideas stands the test of the LHC
data will govern the course of particle physics in the subsequent decades
Sparticle mass hierarchies, simplified models from SUGRA unification, and benchmarks for LHC Run-II SUSY searches
Sparticle mass hierarchies contain significant information regarding the
origin and nature of supersymmetry breaking. The hierarchical patterns are
severely constrained by electroweak symmetry breaking as well as by the
astrophysical and particle physics data. They are further constrained by the
Higgs boson mass measurement. The sparticle mass hierarchies can be used to
generate simplified models consistent with the high scale models. In this work
we consider supergravity models with universal boundary conditions for soft
parameters at the unification scale as well as supergravity models with
nonuniversalities and delineate the list of sparticle mass hierarchies for the
five lightest sparticles. Simplified models can be obtained by a truncation of
these, retaining a smaller set of lightest particles. The mass hierarchies and
their truncated versions enlarge significantly the list of simplified models
currently being used in the literature. Benchmarks for a variety of
supergravity unified models appropriate for SUSY searches at future colliders
are also presented. The signature analysis of two benchmark models has been
carried out and a discussion of the searches needed for their discovery at LHC
RUN-II is given. An analysis of the spin independent neutralino-proton cross
section exhibiting the Higgs boson mass dependence and the hierarchical
patterns is also carried out. It is seen that a knowledge of the spin
independent neutralino-proton cross section and the neutralino mass will narrow
down the list of the allowed sparticle mass hierarchies. Thus dark matter
experiments along with analyses for the LHC Run-II will provide strong clues to
the nature of symmetry breaking at the unification scale.Comment: To appear in JHEP; 37 pages, 11 tables, 11 figure