Understanding the Basis for Down Syndrome Phenotypes

Down syndrome is a collection of features that are caused by trisomy for human Chromosome 21. While elevated transcript levels of the more than 350 genes on the chromosome are primarily responsible, it is likely that multiple genetic mechanisms underlie the numerous ways in which development and function diverge in individuals with trisomy 21 compared to euploid individuals. We consider genotype–phenotype interactions with the goal of producing working concepts that will be useful for approaches to ameliorate the effects of trisomy

Lorentz Violation in Warped Extra Dimensions

Higher dimensional theories which address some of the problematic issues of the Standard Model(SM) naturally involve some form of $D=4+n$-dimensional Lorentz invariance violation (LIV). In such models the fundamental physics which leads to, e.g., field localization, orbifolding, the existence of brane terms and the compactification process all can introduce LIV in the higher dimensional theory while still preserving 4-d Lorentz invariance. In this paper, attempting to capture some of this physics, we extend our previous analysis of LIV in 5-d UED-type models to those with 5-d warped extra dimensions. To be specific, we employ the 5-d analog of the SM Extension of Kostelecky et. al. ~which incorporates a complete set of operators arising from spontaneous LIV. We show that while the response of the bulk scalar, fermion and gauge fields to the addition of LIV operators in warped models is qualitatively similar to what happens in the flat 5-d UED case, the gravity sector of these models reacts very differently than in flat space. Specifically, we show that LIV in this warped case leads to a non-zero bulk mass for the 5-d graviton and so the would-be zero mode, which we identify as the usual 4-d graviton, must necessarily become massive. The origin of this mass term is the simultaneous existence of the constant non-zero $AdS_5$ curvature and the loss of general co-ordinate invariance via LIV in the 5-d theory. Thus warped 5-d models with LIV in the gravity sector are not phenomenologically viable.Comment: 14 pages, 4 figs; discussion added, algebra repaire

Stealth Supersymmetry

We present a broad class of supersymmetric models that preserve R-parity but lack missing energy signatures. These models have new light particles with weak-scale supersymmetric masses that feel SUSY breaking only through couplings to the MSSM. This small SUSY breaking leads to nearly degenerate fermion/boson pairs, with small mass splittings and hence small phase space for decays carrying away invisible energy. The simplest scenario has low-scale SUSY breaking, with missing energy only from soft gravitinos. This scenario is natural, lacks artificial tunings to produce a squeezed spectrum, and is consistent with gauge coupling unification. The resulting collider signals will be jet-rich events containing false resonances that could resemble signatures of R-parity violation. We discuss several concrete examples of the general idea, and emphasize gamma + jet + jet resonances, displaced vertices, and very large numbers of b-jets as three possible discovery modes.Comment: 12 pages, 4 figure

Dijet signals of the Little Higgs model with T-parity

The Littest Higgs model with T-parity (LHT), apart from offering a viable solution to the naturalness problem of the Standard Model, also predicts a set of new fermions as well as a candidate for dark matter. We explore the possibility of discovering the heavy T-odd quark Q_H at the LHC in a final state comprising two hard jets with a large missing transverse momentum. Also discussed is the role of heavy flavor tagging.Comment: Changes in text. Some references adde

Gluino Decay as a Probe of High Scale Supersymmetry Breaking

A supersymmetric standard model with heavier scalar supersymmetric particles has many attractive features. If the scalar mass scale is O(10 - 10^4) TeV, the standard model like Higgs boson with mass around 125 GeV, which is strongly favored by the LHC experiment, can be realized. However, in this scenario the scalar particles are too heavy to be produced at the LHC. In addition, if the scalar mass is much less than O(10^4) TeV, the lifetime of the gluino is too short to be measured. Therefore, it is hard to probe the scalar particles at a collider. However, a detailed study of the gluino decay reveals that two body decay of the gluino carries important information on the scalar scale. In this paper, we propose a test of this scenario by measuring the decay pattern of the gluino at the LHC.Comment: 29 pages, 9 figures; version published in JHE

Discrimination of low missing energy look-alikes at the LHC

The problem of discriminating possible scenarios of TeV scale new physics with large missing energy signature at the Large Hadron Collider (LHC) has received some attention in the recent past. We consider the complementary, and yet unexplored, case of theories predicting much softer missing energy spectra. As there is enough scope for such models to fake each other by having similar final states at the LHC, we have outlined a systematic method based on a combination of different kinematic features which can be used to distinguish among different possibilities. These features often trace back to the underlying mass spectrum and the spins of the new particles present in these models. As examples of "low missing energy look-alikes", we consider Supersymmetry with R-parity violation, Universal Extra Dimensions with both KK-parity conserved and KK-parity violated and the Littlest Higgs model with T-parity violated by the Wess-Zumino-Witten anomaly term. Through detailed Monte Carlo analysis of the four and higher lepton final states predicted by these models, we show that the models in their minimal forms may be distinguished at the LHC, while non-minimal variations can always leave scope for further confusion. We find that, for strongly interacting new particle mass-scale ~600 GeV (1 TeV), the simplest versions of the different theories can be discriminated at the LHC running at sqrt{s}=14 TeV within an integrated luminosity of 5 (30) fb^{-1}.Comment: 40 pages, 10 figures; v2: Further discussions, analysis and one figure added, ordering of certain sections changed, minor modifications in the abstract, version as published in JHE

Distinguishing among Technicolor/Warped Scenarios in Dileptons

Models of dynamical electroweak symmetry breaking usually include new spin-1 resonances, whose couplings and masses have to satisfy electroweak precision tests. We propose to use dilepton searches to probe the underlying structure responsible for satisfying these. Using the invariant mass spectrum and charge asymmetry, we can determine the number, parity, and isospin of these resonances. We pick three models of strong/warped symmetry breaking, and show that each model produces specific features that reflect this underlying structure of electroweak symmetry breaking and cancellations.Comment: Added missing referenc

Altered synapse stability in the early stages of tauopathy

Synapse loss is a key feature of dementia, but it is unclear whether synaptic dysfunction precedes degenerative phases of the disease. Here, we show that even before any decrease in synapse density, there is abnormal turnover of cortical axonal boutons and dendritic spines in a mouse model of tauopathy-associated dementia. Strikingly, tauopathy drives a mismatch in synapse turnover; postsynaptic spines turn over more rapidly, whereas presynaptic boutons are stabilized. This imbalance between pre- and post-synaptic stability coincides with reduced synaptically driven neuronal activity in pre-degenerative stages of the disease

Bigger, Better, Faster, More at the LHC

Multijet plus missing energy searches provide universal coverage for theories that have new colored particles that decay into a dark matter candidate and jets. These signals appear at the LHC further out on the missing energy tail than two-to-two scattering indicates. The simplicity of the searches at the LHC contrasts sharply with the Tevatron where more elaborate searches are necessary to separate signal from background. The searches presented in this article effectively distinguish signal from background for any theory where the LSP is a daughter or granddaughter of the pair-produced colored parent particle without ever having to consider missing energies less than 400 GeV.Comment: 26 pages, 8 Figures. Minor textual changes, typos fixed and references adde

Heavy-light decay topologies as a new strategy to discover a heavy gluon

We study the collider phenomenology of the lightest Kaluza-Klein excitation of the gluon, G*, in theories with a warped extra dimension. We do so by means of a two-site effective lagrangian which includes only the lowest-lying spin-1 and spin-1/2 resonances. We point out the importance of the decays of G* to one SM plus one heavy fermion, that were overlooked in the previous literature. It turns out that, when kinematically allowed, such heavy-light decays are powerful channels for discovering the G*. In particular, we present a parton-level Montecarlo analysis of the final state Wtb that follows from the decay of G* to one SM top or bottom quark plus its heavy partner. We find that at \sqrt{s} = 7 TeV and with 10 fb^{-1} of integrated luminosity, the LHC can discover a KK gluon with mass in the range M_{G*} = (1.8 - 2.2) TeV if its coupling to a pair of light quarks is g_{G*qqbar} = (0.2-0.5) g_3. The same process is also competitive for the discovery of the top and bottom partners as well. We find, for example, that the LHC at \sqrt{s} = 7 TeV can discover a 1 TeV KK bottom quark with an integrated luminosity of (5.3 - 0.61) fb^{-1} for g_{G*qqbar} = (0.2-0.5) g_3.Comment: 36 pages, 13 figures. v2: a few typos corrected, comments added, version published in JHE