Physics Beyond the Standard Model

In these three lectures I review the need to go beyond the Standard Glashow- Weinberg-Salam Model and discuss some of the approaches that are explored in this direction.Comment: 5 pages, contribution to the CERN-Latin-American School of High-Energy Physics, Ibarra, Ecuador, 4 - 17 March 2015

Reconstruction of interacting dark energy models from parameterizations

Models with interacting dark energy can alleviate the cosmic coincidence problem by allowing dark matter and dark energy to evolve in a similar fashion. At a fundamental level, these models are specified by choosing a functional form for the scalar potential and for the interaction term. However, in order to compare to observational data it is usually more convenient to use parameterizations of the dark energy equation of state and the evolution of the dark matter energy density. Once the relevant parameters are fitted it is important to obtain the shape of the fundamental functions. In this paper I show how to reconstruct the scalar potential and the scalar interaction with dark matter from general parameterizations. I give a few examples and show that it is possible for the effective equation of state for the scalar field to cross the phantom barrier when interactions are allowed. I analyze the uncertainties in the reconstructed potential arising from foreseen errors in the estimation of fit parameters and point out that a Yukawa-like linear interaction results from a simple parameterization of the coupling.Comment: 6 pages, 8 figure

Technicolor contribution to lepton + photon + missing energy events at the Tevatron

Events with one lepton, one photon and missing energy are the subject of recent searches at the Fermilab Tevatron. We compute possible contributions to these type of events from the process p pbar --> photon l nu_l nu_tau nubar_tau, where l=e,mu in the context of a Low Scale Technicolor Model. We find that with somewhat tighter cuts than the ones used in the CDF search, it could be possible to either confirm or exclude this model in a small region of its parameter space.Comment: 4 pages, 3 figures. Improved text and figures, including comments and new reference

Limits on a Strong Electroweak Sector from e^+ e^- -> 2gamma + missing E at LEP2

We study the process $e^+ e^- \to \gamma \gamma \nu \bar{\nu}$ in the context of a strong electroweak symmetry breaking model, which can be a source of events with two photons and missing energy at LEP2. We investigate bounds on the model assuming that no deviation is observed from the Standard Model within a given experimental error.Comment: 7 pages, Latex, one figur

Orbital order, stacking defects and spin-fluctuations in the pp-electron molecular solid RbO2_2

We examine magnon and orbiton behavior in localized O$_2$ anti-bonding molecular $\pi^*$ orbitals using an effective Kugel-Khomskii Hamiltonian derived from a two band Hubbard model with hopping parameters taken from {\em ab initio} density functional calculations. The considerable difference between intraband and interband hoppings leads to a strong coupling between the spin wave dispersion and the orbital ground state, providing a straightforward way of experimentally determining the orbital ground state from the measured magnon dispersion. The near degeneracy of different orbital ordered states leads to stacking defects which further modulate spin-fluctuation spectra. Proliferation of orbital domains disrupts long-range magnetic order, thus causing a significant reduction in the observed N\'eel temperature.Comment: 5 pages, 2 figure

STRONGLY COUPLED ELECTROWEAK SYMMETRY BREAKING: IMPLICATIONS OF MODELS

We discuss the phenomenology of models of dynamical electroweak symmetry breaking which attempt to generate the observed fermion mass spectrum. After briefly describing the variety of and constraints on proposed models, we concentrate on the signatures of colored pseudo-Nambu-Goldstone bosons and resonances at existing and proposed colliders. These particles provide a possibly unique signature: strongly produced resonances associated with electroweak symmetry breaking. (This is the subgroup report for the ``Electroweak Symmetry Breaking and Beyond the Standard Model" working group of the DPF Long Range Planning Study. This report will appear as a chapter in ``Electroweak Symmetry Breaking and Beyond the Standard Model", edited by T. Barklow, S. Dawson, H.E. Haber, and J. Siegrist, to be published by World Scientific.

The Higgs portal and an unified model for dark energy and dark matter

We examine a scenario where the Higgs boson is coupled to an additional singlet scalar field which we identify with a quintessence field. We show that this results in an unified picture of dark matter and dark energy, where dark energy is the zero-mode classical field rolling the usual quintessence potential and the dark matter candidate is the quantum excitation (particle) of the field, which is produced in the universe due to its coupling to the Higgs boson.Comment: 5 pages, no figures. New references and acknowledgment adde