901 research outputs found
126 GeV Higgs Boson Associated with D-term Triggered Dynamical Supersymmetry Breaking
Continuing with our previous work on D-term triggered dynamical supersymmetry
breaking, we consider a system in which our generic N=1 action is minimally
extended to include the pair of Higgs doublet superfields charged under the
overall U(1) as well as mu and B mu terms. The gauge group is taken to be
SU(3)_C times SU(2)_L times U(1)_Y times U(1). We point out, among other
things, that the Higgs mass less than the Z-boson mass at tree level can be
pushed up to be around 126 GeV by D-term contributions of the overall U(1).
This is readily realized by taking a U(1) gauge coupling of O(1).Comment: 11 pages, 1 figure, A reference corrected, the argument of anomaly
cancellation for an overall U(1) adde
Electroweak precision measurements in supersymmetric models with a U(1)R lepton number
As experimental constraints on the parameter space of the MSSM and close
variations thereof become stronger, the motivation to explore supersymmetric
models that challenge some of the standard assumptions of the MSSM also become
stronger. For example, models where the gauginos are Dirac instead of Majorana
have recently received more attention. Beside allowing for a supersoft SUSY
breaking mechanism where the gauginos only provide finite threshold corrections
to scalar masses, the cross section for the production of a squark pairs is
reduced. In addition, Dirac gauginos can be used to build models that possess a
U(1)R symmetry. This symmetry can then be identified with a lepton number,
leading to models that are quite different from conventional scenarios. The
sneutrinos in these models can acquire a vev and give mass to the leptons and
the down-type squark. The phenomenology is novel, combining signatures that are
typical of R-parity violating scenarios with signatures arising from
leptoquarks. Correspondingly the constraints from electroweak precision data
are also different. In these models, one of the leptons mixes with gauginos and
superpotential Yukawa couplings can contribute to EWPM at tree level. In
addition, lepton universality is broken. In this paper we adapt the operators
analysis of Han and Skiba [1] to include the relevant violation of lepton
universality, and do a global fit of the model to electroweak precision data,
including all relevant tree-level and loop-level effects. We obtain bounds on
the vev of the sneutrino and on the superpotential couplings of the model.Comment: 18 pages, 6 figures, references adde
in lepton number model with a right-handed neutrino
We perform a detailed study of the signal rate of the lightest Higgs boson in
the diphoton channel (), recently analyzed by both the
ATLAS and CMS collaborations at the Large Hadron Collider, in the framework of
lepton number model with a right handed neutrino superfield. The
corresponding neutrino Yukawa coupling, `', plays a very important role in
the phenomenology of this model. A large value of provides
an additional tree level contribution to the lightest Higgs boson mass along
with a very light (mass a few hundred MeV) bino like neutralino and a
small tree level mass of one of the active neutrinos that is compatible with
various experimental results. In the presence of this light neutralino, the
invisible decay width of the Higgs boson can become important. We studied this
scenario in conjunction with the recent LHC results. The signal rate
obtained in this scenario is compatible with the recent
results from both the ATLAS and the CMS collaborations at 1 level. A
small value of `', on the other hand, is compatible with a sterile neutrino
acting as a 7 keV dark matter that can explain the observation of a
mono-energetic X-ray photon line by the XMM-Newton X-ray observatory. We also
study the impact of in this case.Comment: 45 pages, Corrected a sign error in the numerical code and included
the correct symmetry factor in Eq.(B.8). One figure removed, some
modifications in the text, conclusions partially changed. Erratum published
in JHE
Supersymmetry Breaking and Gauge Mediation
We review recent works on supersymmetry breaking and gauge mediation. We
survey our current understanding of dynamical supersymmetry breaking mechanisms
and describe new model building tools using duality, meta-stability, and
stringy construction. We discuss phenomenological constraints and their
solutions, paying attentions to issues with gaugino masses and electroweak
symmetry breaking.Comment: 42 pages, 9 figures, invited review to appear in Annu. Rev. Nucl.
Part. Sci. v2: references adde
Single-Scale Natural SUSY
We consider the prospects for natural SUSY models consistent with current
data. Recent constraints make the standard paradigm unnatural so we consider
what could be a minimal extension consistent with what we now know. The most
promising such scenarios extend the MSSM with new tree-level Higgs interactions
that can lift its mass to at least 125 GeV and also allow for flavor-dependent
soft terms so that the third generation squarks are lighter than current bounds
on the first and second generation squarks. We argue that a common feature of
almost all such models is the need for a new scale near 10 TeV, such as a scale
of Higgsing or confinement of a new gauge group. We consider the question
whether such a model can naturally derive from a single mass scale associated
with supersymmetry breaking. Most such models simply postulate new scales,
leaving their proximity to the scale of MSSM soft terms a mystery. This
coincidence problem may be thought of as a mild tuning, analogous to the usual
mu problem. We find that a single mass scale origin is challenging, but suggest
that a more natural origin for such a new dynamical scale is the gravitino
mass, m_{3/2}, in theories where the MSSM soft terms are a loop factor below
m_{3/2}. As an example, we build a variant of the NMSSM where the singlet S is
composite, and the strong dynamics leading to compositeness is triggered by
masses of order m_{3/2} for some fields. Our focus is the Higgs sector, but our
model is compatible with a light stop (with the other generation squarks heavy,
or with R-parity violation or another mechanism to hide them from current
searches). All the interesting low-energy mass scales, including linear terms
for S playing a key role in EWSB, arise dynamically from the single scale
m_{3/2}. However, numerical coefficients from RG effects and wavefunction
factors in an extra dimension complicate the otherwise simple story.Comment: 32 pages, 3 figures; version accepted by JHE
Light third-generation squarks from flavour gauge messengers
We study models of gauge-mediated supersymmetry breaking with a gauged
horizontal SU(3)_F symmetry acting on the quark superfields. If SU(3)_F is
broken non-supersymmetrically by F-term vacuum expectation values, the massive
gauge bosons and gauginos become messengers for SUSY breaking mediation. These
gauge messenger fields induce a flavour-dependent, negative contribution to the
soft masses of the squarks at one loop. In combination with the soft terms from
standard gauge mediation, one obtains large and degenerate first- and
second-generation squark masses, while the stops and sbottoms are light. We
discuss the implications of this mechanism for the superparticle spectrum and
for flavour precision observables. We also provide an explicit realization in a
model with simultaneous SUSY and SU(3)_F breaking.Comment: 25 pages, 7 figure
Dirac Gauginos in Low Scale Supersymmetry Breaking
It has been claimed that Dirac gaugino masses are necessary for realistic
models of low-scale supersymmetry breaking, and yet very little attention has
been paid to the phenomenology of a light gravitino when gauginos have Dirac
masses. We begin to address this deficit by investigating the couplings and
phenomenology of the gravitino in the effective Lagrangian approach. We pay
particular attention to the phenomenology of the scalar octets, where new decay
channels open up. This leads us to propose a new simplified effective scenario
including only light gluinos, sgluons and gravitinos, allowing the squarks to
be heavy -- with the possible exception of the third generation. Finally, we
comment on the application of our results to Fake Split Supersymmetry.Comment: 40 pages, 3 figures. Minor typos fixed; matches version in Nuclear
Physics
Goldstones in Diphotons
We study the conditions for a new scalar resonance to be observed first in
diphotons at the LHC Run-2. We focus on scenarios where the scalar arises
either from an internal or spacetime symmetry broken spontaneously, for which
the mass is naturally below the cutoff and the low-energy interactions are
fixed by the couplings to the broken currents, UV anomalies, and selection
rules. We discuss the recent excess in diphoton resonance searches observed by
ATLAS and CMS at 750 GeV, and explore its compatibility with other searches at
Run-1 and its interpretation as Goldstone bosons in supersymmetry and composite
Higgs models. We show that two candidates naturally emerge: a Goldstone boson
from an internal symmetry with electromagnetic anomalies, and the scalar
partner of the Goldstone of supersymmetry breaking: the sgoldstino. The dilaton
from conformal symmetry breaking is instead disfavoured by present data, in its
minimal natural realization.Comment: 18 pages + refs, 2 figures. v2: typos corrected, references added,
discussions extended and three new plots. Conclusion unchanged. v3: published
versio
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