1,599 research outputs found
Distinguishing Various Models of the 125 GeV Boson in Vector Boson Fusion
The hint of a new particle around 125 GeV at the LHC through the decay modes
of diphoton and a number of others may point to quite a number of
possibilities. While at the LHC the dominant production mechanism for the Higgs
boson of the standard model and some other extensions is via the gluon fusion
process, the alternative vector boson fusion is more sensitive to electroweak
symmetry breaking through the gauge-Higgs couplings and therefore can be used
to probe for models beyond the standard model. In this work, using the well
known dijet-tagging technique to single out the vector boson fusion mechanism,
we investigate its capability to discriminate a number of models that have been
suggested to give an enhanced inclusive diphoton production rate, including the
standard model Higgs boson, fermiophobic Higgs boson, Randall-Sundrum radion,
inert-Higgs-doublet model, two-Higgs-doublet model, and the MSSM. The rates in
vector-boson fusion can give more information of the underlying models to help
distinguishing among the models.Comment: 31 pages, 3 figures; in this version some wordings are change
The Spectrum of Goldstini and Modulini
When supersymmetry is broken in multiple sectors via independent dynamics,
the theory furnishes a corresponding multiplicity of "goldstini" degrees of
freedom which may play a substantial role in collider phenomenology and
cosmology. In this paper, we explore the tree-level mass spectrum of goldstini
arising from a general admixture of F-term, D-term, and almost no-scale
supersymmetry breaking, employing non-linear superfields and a novel gauge
fixing for supergravity discussed in a companion paper. In theories of F-term
and D-term breaking, goldstini acquire a mass which is precisely twice the
gravitino mass, while the inclusion of no-scale breaking renders one of these
modes, the modulino, massless. We argue that the vanishing modulino mass can be
explained in terms of an accidental and spontaneously broken "global"
supersymmetry.Comment: 10 pages, 2 figures; v2: typo corrected, references updated; v3:
version to appear in JHE
Radion Dynamics and Phenomenology in the Linear Dilaton Model
We investigate the properties of the radion in the 5D linear dilaton model
arising from Little String Theory. A Goldberger-Wise type mechanism is used to
stabilise a large interbrane distance, with the dilaton now playing the role of
the stabilising field. We consider the coupled fluctuations of the metric and
dilaton fields and identify the physical scalar modes of the system. The
wavefunctions and masses of the radion and Kaluza-Klein modes are calculated,
giving a radion mass of order the curvature scale. As a result of the direct
coupling between the dilaton and Standard Model fields, the radion couples to
the SM Lagrangian, in addition to the trace of the energy-momentum tensor. The
effect of these additional interaction terms on the radion decay modes is
investigated, with a notable increase in the branching fraction to photons. We
also consider the effects of a non-minimal Higgs coupling to gravity, which
introduces a mixing between the Higgs and radion modes. Finally, we calculate
the production cross section of the radion at the LHC and use the current Higgs
searches to place constraints on the parameter space.Comment: 28 pages, 7 figures; v2: error in radion-gauge boson Feynman rules
corrected, version published in JHE
The Two Faces of Anomaly Mediation
Anomaly mediation is a ubiquitous source of supersymmetry (SUSY) breaking
which appears in almost every theory of supergravity. In this paper, we show
that anomaly mediation really consists of two physically distinct phenomena,
which we dub "gravitino mediation" and "Kahler mediation". Gravitino mediation
arises from minimally uplifting SUSY anti-de Sitter (AdS) space to Minkowski
space, generating soft masses proportional to the gravitino mass. Kahler
mediation arises when visible sector fields have linear couplings to SUSY
breaking in the Kahler potential, generating soft masses proportional to beta
function coefficients. In the literature, these two phenomena are lumped
together under the name "anomaly mediation", but here we demonstrate that they
can be physically disentangled by measuring associated couplings to the
goldstino. In particular, we use the example of gaugino soft masses to show
that gravitino mediation generates soft masses without corresponding goldstino
couplings. This result naively violates the goldstino equivalence theorem but
is in fact necessary for supercurrent conservation in AdS space. Since
gravitino mediation persists even when the visible sector is sequestered from
SUSY breaking, we can use the absence of goldstino couplings as an unambiguous
definition of sequestering.Comment: 21 pages, 1 table; v2, references added, extended discussion in
introduction and appendix; v3, JHEP versio
Low-Energy Signals from Kinetic Mixing with a Warped Abelian Hidden Sector
We investigate the detailed phenomenology of a light Abelian hidden sector in
the Randall-Sundrum framework. Relative to other works with light hidden
sectors, the main new feature is a tower of hidden Kaluza-Klein vectors that
kinetically mix with the Standard Model photon and Z. We investigate the decay
properties of the hidden sector fields in some detail, and develop an approach
for calculating processes initiated on the ultraviolet brane of a warped space
with large injection momentum relative to the infrared scale. Using these
results, we determine the detailed bounds on the light warped hidden sector
from precision electroweak measurements and low-energy experiments. We find
viable regions of parameter space that lead to significant production rates for
several of the hidden Kaluza-Klein vectors in meson factories and fixed-target
experiments. This offers the possibility of exploring the structure of an extra
spacetime dimension with lower-energy probes.Comment: (1+32) Pages, 13 Figures. v2: JHEP version (minor modifications,
results unchanged
The Higgs as a Probe of Supersymmetric Extra Sectors
We present a general method for calculating the leading contributions to h ->
gg and h -> gamma gamma in models where the Higgs weakly mixes with a nearly
supersymmetric extra sector. Such mixing terms can play an important role in
raising the Higgs mass relative to the value expected in the MSSM. Our method
applies even when the extra sector is strongly coupled, and moreover does not
require a microscopic Lagrangian description. Using constraints from holomorphy
we fix the leading parametric form of the contributions to these Higgs
processes, including the Higgs mixing angle dependence, up to an overall
coefficient. Moreover, when the Higgs is the sole source of mass for a
superconformal sector, we show that even this coefficient is often calculable.
For appropriate mixing angles, the contribution of the extra states to h -> gg
and h -> gamma gamma can vanish. We also discuss how current experimental
limits already lead to non-trivial constraints on such models. Finally, we
provide examples of extra sectors which satisfy the requirements necessary to
use the holomorphic approximation.Comment: v4: 34 pages, 2 figures, typo corrected and clarification adde
Higgs After the Discovery: A Status Report
Recently, the ATLAS and CMS collaborations have announced the discovery of a
125 GeV particle, commensurable with the Higgs boson. We analyze the 2011 and
2012 LHC and Tevatron Higgs data in the context of simplified new physics
models, paying close attention to models which can enhance the diphoton rate
and allow for a natural weak-scale theory. Combining the available LHC and
Tevatron data in the ZZ* 4-lepton, WW* 2-lepton, diphoton, and b-bbar channels,
we derive constraints on the effective low-energy theory of the Higgs boson. We
map several simplified scenarios to the effective theory, capturing numerous
new physics models such as supersymmetry, composite Higgs, dilaton. We further
study models with extended Higgs sectors which can naturally enhance the
diphoton rate. We find that the current Higgs data are consistent with the
Standard Model Higgs boson and, consequently, the parameter space in all models
which go beyond the Standard Model is highly constrained.Comment: 37 pages; v2: ATLAS dijet-tag diphoton channel added, dilaton and
doublet-singlet bugs corrected, references added; v3: ATLAS WW channel
included, comments and references adde
Supersymmetry with Light Stops
Recent LHC data, together with the electroweak naturalness argument, suggest
that the top squarks may be significantly lighter than the other sfermions. We
present supersymmetric models in which such a split spectrum is obtained
through "geometries": being "close to" electroweak symmetry breaking implies
being "away from" supersymmetry breaking, and vice versa. In particular, we
present models in 5D warped spacetime, in which supersymmetry breaking and
Higgs fields are located on the ultraviolet and infrared branes, respectively,
and the top multiplets are localized to the infrared brane. The hierarchy of
the Yukawa matrices can be obtained while keeping near flavor degeneracy
between the first two generation sfermions, avoiding stringent constraints from
flavor and CP violation. Through the AdS/CFT correspondence, the models can be
interpreted as purely 4D theories in which the top and Higgs multiplets are
composites of some strongly interacting sector exhibiting nontrivial dynamics
at a low energy. Because of the compositeness of the Higgs and top multiplets,
Landau pole constraints for the Higgs and top couplings apply only up to the
dynamical scale, allowing for a relatively heavy Higgs boson, including m_h =
125 GeV as suggested by the recent LHC data. We analyze electroweak symmetry
breaking for a well-motivated subset of these models, and find that fine-tuning
in electroweak symmetry breaking is indeed ameliorated. We also discuss a flat
space realization of the scenario in which supersymmetry is broken by boundary
conditions, with the top multiplets localized to a brane while other matter
multiplets delocalized in the bulk.Comment: 27 pages, 7 figure
Global Analysis of the Higgs Candidate with Mass ~ 125 GeV
We analyze the properties of the Higgs candidate with mass ~ 125 GeV
discovered by the CMS and ATLAS Collaborations, constraining the possible
deviations of its couplings from those of a Standard Model Higgs boson. The
CMS, ATLAS and Tevatron data are compatible with Standard Model couplings to
massive gauge bosons and fermions, and disfavour several types of composite
Higgs models unless their couplings resemble those in the Standard Model. We
show that the couplings of the Higgs candidate are consistent with a linear
dependence on particle masses, scaled by the electroweak scale ~ 246 GeV, the
power law and the mass scale both having uncertainties ~ 20%.Comment: 22 pages, 9 figures, v2 incorporates experimental data released
during July 2012 and corrected (and improved) treatment of mass dependence of
coupling
Judging in the Genomic era: judges’ genetic knowledge, confidence and need for training
Genetic information is increasingly used in many contexts, including health, insurance, policing and sentencing – with numerous potential benefits and risks. Protecting from the related risks requires updates to laws and procedures by justice systems. These updates depend to a large extent on what the key stakeholders – the judiciary – know and think about the use of genetic information. This study used a battery of 25 genetic knowledge items to collect data from 73 supreme court judges from the same country (Romania) on their knowledge of genetic information. Their responses were compared with those of two other groups: lawyers (but not judges; N = 94) and nonlawyers (N = 116) from the same country. The data were collected at approximately the same time from the three groups. The judges’ results were also compared to the results obtained from a general population data collection (N = 5310). The results showed that: 1) judges had overall better knowledge of genetics than the other groups, but their knowledge was uneven across different genetic concepts; 2) judges were overall more confident in their knowledge than the other two groups, but their confidence was quite low; and 3) the correlation between knowledge and confidence was moderate for judges, weak for lawyers and not significant for non-lawyers. Finally, 100% of the judges agreed that information on gene-environment processes should be included in judges’ training. Increasing genetic expertise of the justice stakeholders is an important step towards achieving adequate legal protection against genetic data misuse
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