Beyond the Standard Model: LHC Phenomenology, Cosmology from Post-Inflationary Sources, and Dark Matter Physics

TL;DR

This dissertation explores beyond-standard-model theories addressing neutrino masses, dark matter, Higgs vacuum stability, and cosmological observations, proposing new models and potential observable signals at the LHC and in gravitational wave data.

Contribution

It introduces a D-brane inspired extension of the standard model, links cosmological data with dark matter models, and investigates gravitational wave signatures from phase transitions.

Findings

Extended model explains excess relativistic degrees of freedom.

Dark matter candidate with specific annihilation cross section.

Potential gravitational wave signals from phase transitions.

Abstract

It is the goal of this dissertation to demonstrate that beyond the standard model, certain theories exist which solve conflicts between observation and theory -- conflicts such as massive neutrinos, dark matter, unstable Higgs vacuum, and recent Planck observations of excess relativistic degrees of freedom in the early universe. Theories explored include a D-brane inspired construct of U(3) X Sp(1) X U(1) X U(1) extension of the standard model, in which we demonstrate several possible observables that may be detected at the LHC, and an ability to stabilize the Higgs mechanism. The extended model can also explain recent Planck data which, when added to HST data gives an excess of relativistic degrees of freedom of \Delta N = 0.574 +- 0.25 above the standard result. Also explored is a possible non-thermal dark matter model for explanation of this result. Recent observations of Fermi bubble results indicate a signal of a 50 GeV dark matter particle annihilating into b b-bar, with a thermally averaged annihilation cross section corresponding to < \sigma v> = 8 X 10^(-27) cm^3/s, spurs interest in a Higgs portal model suggested by Steven Weinberg. Other implications of this model are also explored such as its ability to explain dark matter direct detection results along with LHC Higgs data, and Planck data. Particle physics is complimented by possible stochastic gravitational wave searches for which a model of second order global phase transitions is explored. These transitions generate gravitational wave spectra with amplitudes of order \Omega_{gw} h^2 = 10^(-24) - 10^(-15). Furthermore, techniques into such calculations are investigated in hopes to improve the stability required in such lattice simulations.