Dark Matter Production Mechanisms with a Non-Thermal Cosmological History - A Classification

We perform a comprehensive study of models of dark matter (DM) in a Universe with a non-thermal cosmological history, i.e with a phase of pressure-less matter domination before the onset of big-bang nucleosynethesis (BBN). Such cosmological histories are generically predicted by UV completions that contain gravitationally coupled scalar fields (moduli). We classify the different production mechanisms for DM in this framework, generalizing previous works by considering a wide range of DM masses/couplings and allowing for DM to be in equilibrium with a dark sector. We identify four distinct parametric regimes for the production of relic DM, and derive accurate semi-analytic approximations for the DM relic abundance. Our results are particularly relevant for supersymmetric theories, in which the standard non-thermally produced DM candidates are disfavored by indirect detection constraints. We also comment on experimental signals in this framework, focusing on novel effects involving the power spectrum of DM density perturbations. In particular, we identify a class of models where the spectrum of DM density perturbations is sensitive to the pressure-less matter dominated era before BBN, giving rise to interesting astrophysical signatures to be looked for in the future. A worthwhile future direction would be to study well-motivated theoretical models within this framework and carry out detailed studies of the pattern of expected experimental signals.

Superpartners at LHC and Future Colliders: Predictions from Constrained Compactified M-Theory

We study a realistic top-down M-theory compactification with low-scale effective Supersymmetry, consistent with phenomenological constraints. A combination of top-down and generic phenomenological constraints fix the spectrum. The gluino mass is predicted to be about 1.5 TeV. Three and only three superpartner channels, $tilde{g} tilde{g}$, $chi_2^0 chi_1^pm$ and $chi_1^+ chi_1^-$ (where $chi_2^0, chi_1^pm$ are Wino-like), are expected to be observable at LHC-14. We also investigate the prospects of finding heavy squarks and Higgsinos at future colliders. Gluino-stop-top, gluino-sbottom-bottom associated production and first generation squark associated production should be observable at a 100 TeV collider, along with direct production of heavy Higgsinos. Within this framework the discovery of a single sparticle is sufficient to determine uniquely the SUSY spectrum, yielding a number of concrete testable predictions for LHC-14 and future colliders, and determination of $M_{3/2}$ and thereby other fundamental quantities.

R-Parity Conservation from a Top Down Perspective

Motivated by results from the LHC and dark matter searches, we study the possibility of phenomenologically viable R-parity violation in $SU(5)$ GUT models from a top-down point of view. We show that in contrast to the more model dependent bounds on the proton lifetime, the limits on neutrino masses provide a robust, stringent and complementary constraint on all $SU(5)$ GUT-based R-parity violating models. Focusing on well-motivated string/$M$ theory GUT frameworks with mechanisms for doublet-triplet splitting and a solution to the $mu/Bmu$ problems, we show that imposing the neutrino mass bounds implies that R-parity violation is disfavored. The arguments can also be generalized to minimal $SO(10)$ GUTs. An experimental observation of R-parity violation would, therefore, disfavor such classes of top-down GUT models.