453 research outputs found
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 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
GUT-based R-parity violating models. Focusing on well-motivated string/
theory GUT frameworks with mechanisms for doublet-triplet splitting and a
solution to the problems, we show that imposing the neutrino mass
bounds implies that R-parity violation is disfavored. The arguments can also be
generalized to minimal 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 -MSSM - An Theory motivated model of Particle Physics
We continue our study of the low energy implications of theory vacua on
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 -MSSM, can be naturally defined within the above framework. In
this paper, we study some of the important phenomenological features of the
-MSSM. In particular, the soft supersymmetry breaking parameters and the
superpartner spectrum are computed. The -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
-MSSM is also naturally consistent with precision gauge coupling
unification. The phenomenological consequences for cosmology and collider
physics of the -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 arising from Theory
compactified on a -manifold. This is linked to the problem of the breaking
of the extra gauge group, in the subgroup of
, 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 which originate from
string/ theory on 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/-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 .
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 collider with 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
-inos compose the heavier chargino states (), though it is
straightforward to consider the reverse situation also. We show that in such
scenarios -inos decay into , and plus neutralinos almost
universally. In the 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 of integrated luminosity, -inos could be discovered
(excluded) up to 1.1 (1.8) TeV if the spectrum is not compressed.Comment: 19 pages, 9 figure
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