200 research outputs found
A Higgs Mass Shift to 125 GeV and A Multi-Jet Supersymmetry Signal: Miracle of the Flippons at the \sqrt{s} = 7 TeV LHC
We describe a model named No-Scale F-SU(5) which is simultaneously capable of
explaining the dual signals emerging at the LHC of i) a 124-126 GeV Higgs boson
mass m_h, and ii) tantalizing low-statistics excesses in the multi-jet data
which may attributable to supersymmetry. These targets tend to be mutually
exclusive in more conventional approaches. The unified mechanism responsible
for both effects is the introduction of a rather unique set of vector-like
multiplets at the TeV scale, dubbed flippons, which i) can elevate m_h by
around 3-4 GeV via radiative loop corrections, and ii) flatten the running of
the strong coupling and color-charged gaugino, resulting in a prominent
collider signal from production of light gluino pairs. This well motivated
theoretical framework maintains consistency with all key phenomenological
constraints, and all residual parameterization freedom may in principle be
fixed by a combination of the two experiments described. We project that the
already collected luminosity of 5 fb^-1 may be sufficient to definitively
establish the status of this model, given appropriate data selection cuts.Comment: Physics Letters B version, 10 pages, 3 figures, 2 tables. arXiv admin
note: text overlap with arXiv:1105.398
The Tevatron at the Frontier of Dark Matter Direct Detection
Direct detection of dark matter (DM) requires an interaction of dark matter
particles with nucleons. The same interaction can lead to dark matter pair
production at a hadron collider, and with the addition of initial state
radiation this may lead to mono-jet signals. Mono-jet searches at the Tevatron
can thus place limits on DM direct detection rates. We study these bounds both
in the case where there is a contact interaction between DM and the standard
model and where there is a mediator kinematically accessible at the Tevatron.
We find that in many cases the Tevatron provides the current best limit,
particularly for light dark matter, below 5 GeV, and for spin dependent
interactions. Non-standard dark matter candidates are also constrained. The
introduction of a light mediator significantly weakens the collider bound. A
direct detection discovery that is in apparent conflict with mono-jet limits
will thus point to a new light state coupling the standard model to the dark
sector. Mono-jet searches with more luminosity and including the spectrum shape
in the analysis can improve the constraints on DM-nucleon scattering cross
section.Comment: 20 pages, 8 figures, final version in JHE
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
Decaying Dark Matter can explain the electron/positron excesses
PAMELA and ATIC recently reported excesses in e+ e- cosmic rays. Since the
interpretation in terms of DM annihilations was found to be not easily
compatible with constraints from photon observations, we consider the DM decay
hypothesis and find that it can explain the e+ e- excesses compatibly with all
constraints, and can be tested by dedicated HESS observations of the Galactic
Ridge. ATIC data indicate a DM mass of about 2 TeV: this mass naturally implies
the observed DM abundance relative to ordinary matter if DM is a quasi-stable
composite particle with a baryon-like matter asymmetry. Technicolor naturally
yields these type of candidates.Comment: 20 pages, 7 figure
Two component dark matter
We explain the PAMELA positron excess and the PPB-BETS/ATIC e+ + e- data
using a simple two component dark matter model (2DM). The two particle species
in the dark matter sector are assumed to be in thermal equilibrium in the early
universe. While one particle is stable and is the present day dark matter, the
second one is metastable and decays after the universe is 10^-8 s old. In this
model it is simple to accommodate the large boost factors required to explain
the PAMELA positron excess without the need for large spikes in the local dark
matter density. We provide the constraints on the parameters of the model and
comment on possible signals at future colliders.Comment: 6 pages, 2 figures, discussion clarified and extende
Atmospheric Neutrinos Can Make Beauty Strange
The large observed mixing angle in atmospheric neutrinos, coupled with Grand
Unification, motivates the search for a large mixing between right-handed
strange and bottom squarks. Such mixing does not appear in the standard CKM
phenomenology, but may induce significant b to s transitions through gluino
diagrams. Working in the mass eigenbasis, we show quantitatively that an order
one effect on CP violation in B_d to phi+K_S is possible due to a large mixing
between right-handed b and s squarks, while still satisfying constraints from b
to s + gamma. We also include the effect of right- and left-handed bottom
squark mixing proportional to m_b*mu*tan(beta). For small mu*tan(beta) there
may also be a large effect in B_s mixing correlated with a large effect in B_d
to phi+K_S, typically mixing effects are greater than 100 ps^{-1}, an
unambiguous signal of new physics at Tevatron Run II.Comment: 32 pages, LaTeX. Corrected a factor of two mistake in the code; the
possible impact on B -> phi K_s became larger. Figures and discussion
updated, a reference adde
Astrophysical Uncertainties in the Cosmic Ray Electron and Positron Spectrum From Annihilating Dark Matter
In recent years, a number of experiments have been conducted with the goal of
studying cosmic rays at GeV to TeV energies. This is a particularly interesting
regime from the perspective of indirect dark matter detection. To draw reliable
conclusions regarding dark matter from cosmic ray measurements, however, it is
important to first understand the propagation of cosmic rays through the
magnetic and radiation fields of the Milky Way. In this paper, we constrain the
characteristics of the cosmic ray propagation model through comparison with
observational inputs, including recent data from the CREAM experiment, and use
these constraints to estimate the corresponding uncertainties in the spectrum
of cosmic ray electrons and positrons from dark matter particles annihilating
in the halo of the Milky Way.Comment: 21 pages, 9 figure
Decaying Dark Matter in Supersymmetric Model and Cosmic-Ray Observations
We study cosmic-rays in decaying dark matter scenario, assuming that the dark
matter is the lightest superparticle and it decays through a R-parity violating
operator. We calculate the fluxes of cosmic-rays from the decay of the dark
matter and those from the standard astrophysical phenomena in the same
propagation model using the GALPROP package. We reevaluate the preferred
parameters characterizing standard astrophysical cosmic-ray sources with taking
account of the effects of dark matter decay. We show that, if energetic leptons
are produced by the decay of the dark matter, the fluxes of cosmic-ray positron
and electron can be in good agreements with both PAMELA and Fermi-LAT data in
wide parameter region. It is also discussed that, in the case where sizable
number of hadrons are also produced by the decay of the dark matter, the mass
of the dark matter is constrained to be less than 200-300 GeV in order to avoid
the overproduction of anti-proton. We also show that the cosmic gamma-ray flux
can be consistent with the results of Fermi-LAT observation if the mass of the
dark matter is smaller than nearly 4 TeV.Comment: 24 pages, 5 figure
The Supersymmetric Standard Models with Decay and Stable Dark Matters
We propose two supersymmetric Standard Models (SMs) with decaying and stable
dark matter (DM) particles. To explain the SM fermion masses and mixings and
have a heavy decay DM particle S, we consider the Froggatt-Nielsen mechanism by
introducing an anomalous U(1)_X gauge symmetry. Around the string scale, the
U(1)_X gauge symmetry is broken down to a Z_2 symmetry under which S is odd
while all the SM particles are even. S obtains a vacuum expectation value
around the TeV scale, and then it can three-body decay dominantly to the
second/third family of the SM leptons in Model I and to the first family of the
SM leptons in Model II. Choosing a benchmark point in the constrained minimal
supersymmetric SM with exact R parity, we show that the lightest neutralino DM
is consistent with the CDMS II experiment. Considering S three-body decay and
choosing suitable parameters, we show that the PAMELA and Fermi-LAT experiments
and the PAMELA and ATIC experiments can be explained in Model I and Model II,
respectively.Comment: RevTex4, 26 pages, 6 figures, references added, version to appear in
EPJ
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