105 research outputs found
High Scale Physics Connection to LHC Data
The existing data appears to provide hints of an underlying high scale
theory. These arise from the gauge coupling unification, from the smallness of
the neutrino masses, and via a non-vanishing muon anomaly. An overview of high
scale models is given with a view to possible tests at the Large Hadron
Collider. Specifically we discuss here some generic approaches to deciphering
their signatures. We also consider an out of the box possibility of a four
generation model where the fourth generation is a mirror generation rather than
a sequential generation. Such a scenario can lead to some remarkably distinct
signatures at the LHC.Comment: 23 pages, no figures. Based on invited lectures at the 46th Course at
the International School of Subnuclear Physics- Erice -Sicily: 29 August -7
September, 200
The Footprint of F-theory at the LHC
Recent work has shown that compactifications of F-theory provide a
potentially attractive phenomenological scenario. The low energy
characteristics of F-theory GUTs consist of a deformation away from a minimal
gauge mediation scenario with a high messenger scale. The soft scalar masses of
the theory are all shifted by a stringy effect which survives to low energies.
This effect can range from 0 GeV up to ~ 500 GeV. In this paper we study
potential collider signatures of F-theory GUTs, focussing in particular on ways
to distinguish this class of models from other theories with an MSSM spectrum.
To accomplish this, we have adapted the general footprint method developed
recently for distinguishing broad classes of string vacua to the specific case
of F-theory GUTs. We show that with only 5 fb^(-1) of simulated LHC data, it is
possible to distinguish many mSUGRA models and low messenger scale gauge
mediation models from F-theory GUTs. Moreover, we find that at 5 fb^(-1), the
stringy deformation away from minimal gauge mediation produces observable
consequences which can also be detected to a level of order ~ +/- 80 GeV. In
this way, it is possible to distinguish between models with a large and small
stringy deformation. At 50 fb^(-1), this improves to ~ +/- 10 GeV.Comment: 85 pages, 37 figure
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
Studying Gaugino Mass Unification at the LHC
We begin a systematic study of how gaugino mass unification can be probed at
the CERN Large Hadron Collider (LHC) in a quasi-model independent manner. As a
first step in that direction we focus our attention on the theoretically
well-motivated mirage pattern of gaugino masses, a one-parameter family of
models of which universal (high scale) gaugino masses are a limiting case. We
improve on previous methods to define an analytic expression for the metric on
signature space and use it to study one-parameter deviations from universality
in the gaugino sector, randomizing over other soft supersymmetry-breaking
parameters. We put forward three ensembles of observables targeted at the
physics of the gaugino sector, allowing for a determination of this
non-universality parameter without reconstructing individual mass eigenvalues
or the soft supersymmetry-breaking gaugino masses themselves. In this
controlled environment we find that approximately 80% of the supersymmetric
parameter space would give rise to a model for which our method will detect
non-universality in the gaugino mass sector at the 10% level with an integrated
luminosity of order 10 inverse femptobarns. We discuss strategies for improving
the method and for adding more realism in dealing with the actual experimental
circumstances of the LHC
The No-Scale Multiverse at the LHC
We present a contemporary perspective on the String Landscape and the
Multiverse of plausible string, M- and F-theory vacua, seeking to demonstrate a
non-zero probability for the existence of a universe matching our own observed
physics within the solution ensemble, arguing for the importance of No-Scale
Supergravity as an essential common underpinning. Our context is a highly
detailed phenomenological probe of No-Scale F-SU(5), a model representing the
intersection of the F-lipped SU(5) X U(1)_X Grand Unified Theory (GUT) with
extra TeV-Scale vector-like multiplets derived out of F-theory, and the
dynamics of No-Scale Supergravity. We present a highly constrained "Golden"
region with tan(beta) \sim 15, m_t = 173.0 - 174.4 GeV, M_1/2 = 455 - 481 GeV,
and M_V = 691 - 1020 GeV, which simultaneously satisfies all known experimental
constraints. We supplement this bottom-up phenomenological perspective with a
top-down theoretical analysis of the one-loop effective Higgs potential,
achieving a striking consonance via the dynamic determination of tan(beta) and
M_1/2 at the local secondary minimization of the spontaneously broken
electroweak Higgs vacuum V_min. We present the distinctive signatures of
No-Scale F-SU(5) at the LHC, where a light stop and gluino are expected to
generate a surplus of ultra-high multiplicity (>= 9) hadronic jet events. We
propose modest alterations to the canonical background selection cut strategy
which would enhance resolution of these events, while readily suppressing the
contribution of all Standard Model processes, and allowing a clear
differentiation from competing models of new physics. Detection by the LHC of
the ultra-high jet signal would constitute a suggestive evocation of the
intimately linked stringy origins of F-SU(5), and could provide a glimpse into
the fundamental string moduli, and possibly even the workings of the No-Scale
Multiverse.Comment: A review of recent work, submitted to the DICE 2010 Workshop
proceedings, based on the invited talk by D.V.N. (20 Pages, 5 Tables, 18
Figures
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
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