Top asymmetry and the search for a light hadronic resonance in association with single top

The exchange of a light $t$-channel flavor-changing gauge boson, \Vp, with mass $\sim m_{top}$ remains a leading explanation for the anomalous forward backward asymmetry in top quark production at the Tevatron. Unlike other ideas, including heavier $t$-channel mediators, the light \Vp model is not easily seen in the \mtt distribution. We advocate a more promising strategy. While current analyses at hadron colliders may not be sensitive, we propose searching for a $jj$ resonance in association with single top that may allow discovery in existing data. Deviations in the lepton charge asymmetry in this sample should also be present.Comment: 5 pages, 2 figur

Top quark asymmetry and dijet resonances

CDF recently reported an anomaly in the $m_{jj}$ distribution of dijet events produced in association with a $W$ boson. If this anomaly is associated with a new flavor conserving vector resonance, $V$, one might have expected to observe effects in the analogous $m_{jj}$ distribution produced in association with a $\gamma$. No such excess is observed. A single $u-t-V$ flavor changing coupling, however, can contribute to the $m_{jj}$ anomaly while being consistent with other resonance searches. Furthermore, it gives a potential explanation of the observed forward-backward asymmetry in top quark production.Comment: 4 pages, 1 figur

Chromatin Structure in the Cellular Slime Mold Dictyostelium discoideum

The structure of Dictyostelium discoideum chromatin has been studied by the following techniques: electron microscopy, staphylococcal nuclease digestion, acrylamide gel electrophoresis, sucrose gradient centrifugation, and melting. The basic unit of chromatin is the nucleosome, which is a particle 98.6 angstrom in diameter. Approximately 50% of the chromatin is protected from nuclease digestion, but this decreases when protease activity is not inhibited. The nucleosome contains 187 base pairs of DNA, including a 137-base-pair core and a 50-base-pair linker. The monomer nucleosome has an s20,w value of 11.5 S on isokinetic sucrose gradients. When the chromatin is melted, four transitions are observed, at 54.5 degrees, 66.7 degrees, 74.9 degrees, and 79.7 degrees. The structure of Dictyostelium chromatin is very similar to that seen in higher eukaryotes

Top quark forward-backward asymmetry from new t-channel physics

Motivated by recent measurements of the top quark forward-backward asymmetry at the Tevatron, we study how t-channel new physics can contribute to a large value. We concentrate on a theory with an abelian gauge boson possessing flavor changing couplings between up and top quarks, but satisfies flavor physics constraints. Collider constraints are strong, but can be consistent with the aid of small flavor diagonal couplings. We find that M_Z' ~ 160 GeV can yield a total lab-frame asymmetry of ~18% without being in conflict with other observables. There are implications for future collider searches, including exotic top quark decays, like-sign top quark production, and detailed measurements of the top production cross section. An alternate model with a gauged non-Abelian flavor symmetry would have similar phenomenology, but lacks the like-sign top signal.Comment: 5 pages, 4 figure

Top quark asymmetry from a non-Abelian horizontal symmetry

Motivated by the persistence of a large measured top quark forward-backward asymmetry at the Tevatron, we examine a model of non-Abelian flavor gauge symmetry. The exchange of the gauge bosons in the $t$-channel can give a large asymmetry due to the forward Rutherford scattering peak. We address generic constraints on non-Abelian $t$-channel physics models including flavor diagonal resonances and potentially dangerous contributions to inclusive top pair cross sections. We caution on the general difficulty of comparing theoretical predictions for top quark signals to the existing experimental results due to potentially important acceptance effects. The first signature at the Large Hadron Collider can be a large inclusive top pair cross section, or like-sign dilepton events, although the latter signal is much smaller than in Abelian models. Deviations of the invariant mass distributions at the LHC will also be promising signatures. A more direct consistency check of the Tevatron asymmetry through the LHC asymmetry is more likely to be relevant at a later stage.Comment: 21 pages, 7 figure

CRiBAC: Community-centric role interaction based access control model

As one of the most efficient solutions to complex and large-scale problems, multi-agent cooperation has been in the limelight for the past few decades. Recently, many research projects have focused on context-aware cooperation to dynamically provide complex services. As cooperation in the multi-agent systems (MASs) becomes more common, guaranteeing the security of such cooperation takes on even greater importance. However, existing security models do not reflect the agents' unique features, including cooperation and context-awareness. In this paper, we propose a Community-based Role interaction-based Access Control model (CRiBAC) to allow secure cooperation in MASs. To do this, we refine and extend our preliminary RiBAC model, which was proposed earlier to support secure interactions among agents, by introducing a new concept of interaction permission, and then extend it to CRiBAC to support community-based cooperation among agents. We analyze potential problems related to interaction permissions and propose two approaches to address them. We also propose an administration model to facilitate administration of CRiBAC policies. Finally, we present the implementation of a prototype system based on a sample scenario to assess the proposed work and show its feasibility. © 2012 Elsevier Ltd. All rights reserved

Comparison of electric dipole moments and the Large Hadron Collider for probing CP violation in triple boson vertices

CP violation from physics beyond the Standard Model may reside in triple boson vertices of the electroweak theory. We review the effective theory description and discuss how CP violating contributions to these vertices might be discerned by electric dipole moments (EDM) or diboson production at the Large Hadron Collider (LHC). Despite triple boson CP violating interactions entering EDMs only at the two-loop level, we find that EDM experiments are generally more powerful than the diboson processes. To give example to these general considerations we perform the comparison between EDMs and collider observables within supersymmetric theories that have heavy sfermions, such that substantive EDMs at the one-loop level are disallowed. EDMs generally remain more powerful probes, and next-generation EDM experiments may surpass even the most optimistic assumptions for LHC sensitivities.Comment: 26 pages, 14 figures, published version with more argument

Development and application of a self-referencing glucose microsensor for the measurement of glucose consumption by pancreatic ?-cells

Glucose gradients generated by an artificial source and ?-cells were measured using an enzyme-based glucose microsensor, 8-?m tip diameter, as a self-referencing electrode. The technique is based on a difference measurement between two locations in a gradient and thus allows us to obtain real-time flux values with minimal impact of sensor drift or noise. Flux values were derived by incorporation of the measured differential current into Fick's first equation. In an artificial glucose gradient, a flux detection limit of 8.2 ± 0.4 pmol·cm-2·s-1 (mean ± SEM, n = 7) with a sensor sensitivity of 7.0 ± 0.4 pA/mM (mean ± SEM, n = 16) was demonstrated. Under biological conditions, the glucose sensor showed no oxygen dependence with 5 mM glucose in the bulk medium. The addition of catalase to the bulk medium was shown to ameliorate surface-dependent flux distortion close to specimens, suggesting an underlying local accumulation of hydrogen peroxide. Glucose flux from ?-cell clusters, measured in the presence of 5 mM glucose, was 61.7 ± 9.5 fmol·nL-1·s-1 (mean ± SEM, n = 9) and could be pharmacologically modulated. Glucose consumption in response to FCCP (1 ?M) transiently increased, subsequently decreasing to below basal by 93 ± 16 and 56 ± 6%, respectively (mean ± SEM, n = 5). Consumption was decreased after the application of 10 ?M rotenone by 74 ± 5% (mean ± SEM, n = 4). These results demonstrate that an enzyme-based amperometric microsensor can be applied in the self-referencing mode. Further, in obtaining glucose flux measurements from small clusters of cells, these are the first recordings of the real-time dynamic of glucose movements in a biological microenvironment. <br/