218 research outputs found
Higgs quartic coupling and neutrino sector evolution in 2UED models
Two compact universal extra dimensional models are an interesting class of
models for different theoretical and phenomenological issues, such as the
justification of having three standard model fermion families, suppression of
proton decay rate, dark matter parity from relics of the 6-dimensional Lorentz
symmetry, origin of masses and mixings in the standard model. However, these
theories are merely effective ones, with typically a reduced range of validity
in their energy scale. We explore two limiting cases of the three standard
model generations all propagating in the bulk or all localised to a brane, from
the point of view of renormalisation group equation evolutions for the Higgs
sector and for the neutrino sector of these models. The recent experimental
results of the Higgs boson from the LHC allow, in some scenarios, stronger
constraints on the cut-off scale to be placed, from the requirement of the
stability of the Higgs potential.Comment: 9 pages, 6 figures, accepted for publication in European Physical
Journal C. arXiv admin note: text overlap with arXiv:1306.485
Large Without the Desert
Even if the unification and supersymmetry breaking scales are around
to TeV, a large coupling may be entirely generated at low
energies through RGE evolution in the 5D MSSM. Independent of the precise
details of supersymmetry breaking, we take advantage of power law running in
five dimensions and a compactification scale in the TeV range to show
how the gluino mass may drive a large enough to achieve the required
GeV Higgs mass. This also allows for sub-TeV stops, possibly observable
at the LHC, and preserving GUT unification, thereby resulting in improved
naturalness properties with respect to the four dimensional MSSM. The results
apply also to models of "split families" in which the first and second
generation matter fields are in the bulk and the third is on the boundary,
which may assist in the generation of light stops whilst satisfying collider
constraints on the first two generations of squarks.Comment: 21 pages, 21 figures. Plots updated to published version, in JHE
Minimal Spin-3/2 Dark Matter in a simple -channel model
We consider a spin~-~3/2 fermionic dark matter candidate (DM) interacting
with Standard Model fermions through a vector mediator in the -channel. We
find that for pure vector couplings almost the entire parameter space of the DM
and mediator mass consistent with the observed relic density is ruled out by
the direct detection observations through DM-nucleon elastic scattering
cross-sections. In contrast, for pure axial-vector coupling, the most stringent
constraints are obtained from mono-jet searches at the Large Hadron Collider.Comment: 8 pages, 5 figures, Version accepted for publication in EPJ
Spin-3/2 dark matter in a simple -channel model
We consider a spin-3/2 fermionic dark matter (DM) particle interacting with
the Standard Model quarks through the exchange of a charged and coloured scalar
or vector mediator in a simple -channel model. It is found that for the
vector mediator case, almost the entire parameter space allowed by the observed
relic density is already ruled out by the direct detection LUX data. No such
bounds exist on the interaction mediated by scalar particles. Monojet + missing
energy searches at the Large Hadron Collider provide the most stringent bounds
on the parameters of the model for this case. The collider bounds put a lower
limit on the allowed DM masses.Comment: Published EPJC versio
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