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

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

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 $\bar{q} q$ 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

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, $T_n \ll T_c$, which can significantly alter the usual phase-transition pattern in 2HD models with $T_n \approx T_c$. 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