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 $\mu/B\mu$ 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.Comment: Citations added, accepted to JHEP with minor revision

The G2G_2-MSSM - An MM Theory motivated model of Particle Physics

We continue our study of the low energy implications of $M$ theory vacua on $G_2$ manifolds, undertaken in \cite{Acharya:2007rc,Acharya:2006ia}, where it was shown that the moduli can be stabilized and a TeV scale generated, with the Planck scale as the only dimensionful input. A well-motivated phenomenological model - the $G_2$-MSSM, can be naturally defined within the above framework. In this paper, we study some of the important phenomenological features of the $G_2$-MSSM. In particular, the soft supersymmetry breaking parameters and the superpartner spectrum are computed. The $G_2$-MSSM generically gives rise to light gauginos and heavy scalars with wino LSPs when one tunes the cosmological constant. Electroweak symmetry breaking is present but fine-tuned. The $G_2$-MSSM is also naturally consistent with precision gauge coupling unification. The phenomenological consequences for cosmology and collider physics of the $G_2$-MSSM will be reported in more detail soon.Comment: 42 pages, 7 figures, one figure corrected, reference adde

Neutrino mass from M Theory SO(10)

We study the origin of neutrino mass from $SO(10)$ arising from $M$ Theory compactified on a $G_2$-manifold. This is linked to the problem of the breaking of the extra $U(1)$ gauge group, in the $SU(5)\times U(1)$ subgroup of $SO(10)$, which we show can achieved via a (generalised) Kolda-Martin mechanism. The resulting neutrino masses arise from a combination of the seesaw mechanism and induced R-parity breaking contributions. The rather complicated neutrino mass matrix is analysed for one neutrino family and it is shown how phenomenologically acceptable neutrino masses can emerge.Comment: 32 pages, 12 figure

SO(10) Grand Unification in M theory on a G2 manifold

We consider Grand Unified Theories based on $SO(10)$ which originate from string/$M$ theory on $G_2$ manifolds or Calabi-Yau spaces with discrete symmetries. In this framework we are naturally led to a novel solution of the doublet-triplet splitting problem previously considered by Dvali which involves an extra vector-like Standard Model family and light, but weakly coupled colour triplets. These additional states are predicted to be accessible at the LHC and also induce R-parity violation. Gauge coupling unification occurs with a larger GUT coupling.Comment: 5 pages, added references, revised argument on equation 18, results unchanged, a new example is given in equation 24, agrees with published version in Physical Review

Categorisation and Detection of Dark Matter Candidates from String/M-theory Hidden Sectors

We study well-motivated dark matter candidates arising from weakly-coupled hidden sectors in compactified string/$M$-theory. Imposing generic top-down constraints greatly restricts allowed candidates. By considering the possible mechanisms for achieving the correct dark matter relic density, we compile categories of viable dark matter candidates and annihilation mediators. We consider the case where supersymmetry breaking occurs via moduli stabilisation and is gravitationally mediated to the visible and other hidden sectors, without assuming sequestering of the sector in which supersymmetry is broken. We find that in this case, weakly-coupled hidden sectors only allow for fermionic dark matter. Additionally, most of the mechanisms for obtaining the full relic density only allow for a gauge boson mediator, such as a dark $Z'$. Given these considerations, we study the potential for discovering or constraining the allowed parameter space given current and future direct detection experiments, and direct production at the LHC. We also present a model of a hidden sector which would contain a satisfactory dark matter candidate.Comment: 29 pages, 10 figure

Prospects for observing charginos and neutralinos at a 100 TeV proton-proton collider

We investigate the prospects for discovering charginos and neutralinos at a future $pp$ collider with $\sqrt{s} = 100$ TeV. We focus on models where squarks and sleptons are decoupled -- as motivated by the LHC data. Our initial study is based on models where Higgsinos form the main component of the LSP and $W$-inos compose the heavier chargino states ($M_2 > \mu$), though it is straightforward to consider the reverse situation also. We show that in such scenarios $W$-inos decay into $W^\pm$, $Z$ and $h$ plus neutralinos almost universally. In the $W Z$ channel we compare signal and background in various kinematical distributions. We design simple but effective signal regions for the trilepton channel and evaluate discovery reach and exclusion limits. Assuming 3000 fb$^{-1}$ of integrated luminosity, $W$-inos could be discovered (excluded) up to 1.1 (1.8) TeV if the spectrum is not compressed.Comment: 19 pages, 9 figure