615 research outputs found
Dark matter from unification
We consider a minimal extension of the Standard Model (SM), which leads to
unification of the SM coupling constants, breaks electroweak symmetry
dynamically by a new strongly coupled sector and leads to novel dark matter
candidates. In this model, the coupling constant unification requires the
existence of electroweak triplet and doublet fermions singlet under QCD and new
strong dynamics underlying the Higgs sector. Among these new matter fields and
a new right handed neutrino, we consider the mass and mixing patterns of the
neutral states. We argue for a symmetry stabilizing the lightest mass
eigenstates of this sector and determine the resulting relic density. The
results are constrained by available data from colliders and direct and
indirect dark matter experiments. We find the model viable and outline briefly
future research directions.Comment: 30 pages, 7 figure
Holographic modelling of a light technidilaton
We present a simplified holographic model of chiral symmetry breaking in
gauge theory. The chiral condensate is represented by a single scalar field in
AdS, with the gauge dynamics input through radial dependence of its mass,
representing the running of the anomalous dimension of the qbar q operator. We
discuss simple examples of the chiral transition out of the conformal window
when the infrared value of the anomalous dimension, \gamma_m, is tuned to one
(equivalently the AdS-scalar mass squared is tuned to the
Breitenlohner-Freedman bound of -4). The output of the model are the masses of
the scalar meson bound states. We show in an explicit example that
if the gradient of the running of the anomalous dimension falls to zero at the
scale where the BF bound violation occurs, so that the theory becomes near
conformal, then the theory possesses a techni-dilaton state that is
parametrically lighter than the dynamically generated quark mass. Indeed the
full spectrum of excited meson states also become light (relative to the
techni-quark mass) as they approach a conformal spectrum.Comment: 8 pages, 8 pdf figures, added discussion of Fig 3 and new reference
Higgs Mechanism via Bose Einstein Condensation
Recently the Bose-Einstein phenomenon has been proposed as possible physical
mechanism underlying the spontaneous symmetry breaking in cold gauge theories.
The mechanism is natural and we use it to drive the electroweak symmetry
breaking. The mechanism can be implemented in different ways while here we
review two simple models in which the Bose-Einstein sector is felt directly or
indirectly by all of the standard model fields. The structure of the
corrections due to the new mechanism is general and independent on the model
used leading to experimental signatures which can be disentangled from other
known extensions of the standard model.Comment: Proceedings for the MRST2003 `Joefest' conference held in Syracuse
University, Syracuse NY, 13-15 May 2003, US
Naturality, unification and dark matter
We consider a model where electroweak symmetry breaking is driven by
Technicolor dynamics with minimal particle content required for walking
coupling and saturation of global anomalies. Furthermore, the model features
three additional Weyl fermions singlet under Technicolor interactions, which
provide for a one-loop unification of the Standard Model gauge couplings. Among
these extra matter fields exists a possible candidate for weakly interacting
dark matter. We evaluate the relic densities and find that they are sufficient
to explain the cosmological observations and avoid the experimental limits from
earth-based searches. Hence, we establish a non-supersymmetric framework where
hierarchy and naturality problems are solved, coupling constant unification is
achieved and a plausible dark matter candidate exists
Baryogenesis in the two doublet and inert singlet extension of the Standard Model
We investigate an extension of the Standard Model containing two Higgs
doublets and a singlet scalar field (2HDSM). We show that the model can have a
strongly first-order phase transition and give rise to the observed baryon
asymmetry of the Universe, consistent with all experimental constraints. In
particular, the constraints from the electron and neutron electric dipole
moments are less constraining here than in pure two-Higgs-doublet model (2HDM).
The two-step, first-order transition in 2HDSM, induced by the singlet field,
may lead to strong supercooling and low nucleation temperatures in comparison
with the critical temperature, , which can significantly alter the
usual phase-transition pattern in 2HD models with .
Furthermore, the singlet field can be the dark matter particle. However, in
models with a strong first-order transition its abundance is typically but a
thousandth of the observed dark matter abundance.Comment: 25 pages, 8 figures; minor changes to match the published versio
Infrared behaviors of SU(2) gauge theory
We will discuss some recent results in the determination of the location of the conformal window in SU(2) gauge theory with N-f fermions in the fundamental representation of the gauge group. In particular, we will demonstrate that the long distance behavior of the continuum theory with N-f = 6 is governed by an infrared stable fixed point.Peer reviewe
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