11,712 research outputs found
Dark matter and neutrino masses in the R-parity violating NMSSM
The R-Parity symmetry Violating (RPV) version of the Next-to-Minimal
Supersymmetric Standard Model (NMSSM) is attractive simultaneously with regard
to the so-called mu-problem and the accommodation of three-flavor neutrino data
at tree level. In this context, we show here that if the Lightest
Supersymmetric Particle (LSP) is the gravitino, it possesses a lifetime larger
than the age of the universe since its RPV induced decay channels are
suppressed by the weak gravitational strength. This conclusion holds if one
considers gravitino masses ~ 10^2 GeV like in supergravity scenarios, and is
robust if the lightest pseudoscalar Higgs field is as light as ~ 10 GeV [as may
occur in the NMSSM]. For these models predicting in particular an RPV
neutrino-photino mixing, the gravitino lifetime exceeds the age of the universe
by two orders of magnitude. However, we find that the gravitino cannot
constitute a viable dark matter candidate since its too large RPV decay widths
would then conflict with the flux data of last indirect detection experiments.
The cases of a sneutrino LSP or a neutralino LSP as well as the more promising
gauge-mediated supersymmetry breaking scenario are also discussed. Both the
one-flavor simplification hypothesis and the realistic scenario of three
neutrino flavors are analyzed. We have modified the NMHDECAY program to extend
the neutralino mass matrix to the present framework.Comment: Latex file, 23 pages, 7 figures. References added and discussion on
the indirect detection modifie
Single superpartner production at Tevatron Run II
We study the single productions of supersymmetric particles at Tevatron Run
II which occur in the processes involving R-parity violating
couplings of type \l'_{ijk} L_i Q_j D_k^c. We focus on the single gaugino
productions which receive contributions from the resonant slepton productions.
We first calculate the amplitudes of the single gaugino productions. Then we
perform analyses of the single gaugino productions based on the three charged
leptons and like sign dilepton signatures. These analyses allow to probe
supersymmetric particles masses beyond the present experimental limits, and
many of the \l'_{ijk} coupling constants down to values smaller than the
low-energy bounds. Finally, we show that the studies of the single gaugino
productions offer the opportunity to reconstruct the , , and masses with a good
accuracy in a model independent way.Comment: 47 pages, epsfi
A Formal Account of the Open Provenance Model
On the Web, where resources such as documents and data are published, shared, transformed, and republished, provenance is a crucial piece of metadata that would allow users to place their trust in the resources they access. The Open Provenance Model (OPM) is a community data model for provenance that is designed to facilitate the meaningful interchange of provenance information between systems. Underpinning OPM is a notion of directed graph, where nodes represent data products and processes involved in past computations, and edges represent dependencies between them; it is complemented by graphical inference rules allowing new dependencies to be derived. Until now, however, the OPM model was a purely syntactical endeavor. The present paper extends OPM graphs with an explicit distinction between precise and imprecise edges. Then a formal semantics for the thus enriched OPM graphs is proposed, by viewing OPM graphs as temporal theories on the temporal events represented in the graph. The original OPM inference rules are scrutinized in view of the semantics and found to be sound but incomplete. An extended set of graphical rules is provided and proved to be complete for inference. The paper concludes with applications of the formal semantics to inferencing in OPM graphs, operators on OPM graphs, and a formal notion of refinement among OPM graphs
Grimoires: Grid Registry with Metadata Oriented Interface: Robustness, Efficiency, Security --- Work-in-Progress
Grid registries allow users to discover resources made available by Grid resource providers. In this paper, we present our on-going work on a next-generation registry, initially designed as part of the myGrid project and to be part of the OMII Grid software release. Specifically, we discuss the support of semantic service descriptions and task/user-specific metadata, along with related performance and security considerations
Measurement of Indeterminacy in Packings of Perfectly Rigid Disks
Static packings of perfectly rigid particles are investigated theoretically
and numerically. The problem of finding the contact forces in such packings is
formulated mathematically. Letting the values of the contact forces define a
vector in a high-dimensional space enable us to show that the set of all
possible contact forces is convex, facilitating its numerical exploration. It
is also found that the boundary of the set is connected with the presence of
sliding contacts, suggesting that a stable packing should not have more than
2M-3N sliding contacts in two dimensions, where M is the number of contacts and
N is the number of particles.
These results were used to analyze packings generated in different ways by
either molecular dynamics or contact dynamics simulations. The dimension of the
set of possible forces and the number of sliding contacts agrees with the
theoretical expectations. The indeterminacy of each component of the contact
forces are found, as well as the an estimate for the diameter of the set of
possible contact forces. We also show that contacts with high indeterminacy are
located on force chains. The question of whether the simulation methods can
represent a packing's memory of its formation is addressed.Comment: 12 pages, 13 figures, submitted to Phys Rev
Intestinal absorption of macromolecules during viral enteritis: an experimental study on rotavirus-infected conventional and germ-free mice.
Epithelial transport and degradation of horseradish peroxidase (HRP), a macromolecular tracer, was studied in conventional and germ-free suckling mice following an experimental infection with rotavirus. Conventional and germ-free mice developed diarrhea from days 2 to 8 postinfection (pi), with growth failure. In mucosal homogenates, infectious virus detected by immunofluorescence on MA 104 cells was present from day 2 through day 8 pi in germ-free mice, but persisted longer (day 13 pi) in conventional mice. Only mild histological lesions were observed during diarrhea, but obvious macrovacuolation of epithelial cells and increased cellular density occurred during the convalescence period (days 9 to 13 pi). Intact and degraded HRP fluxes from mucosa to serosa were measured in vitro on segments of jejunum mounted in Ussing chambers. Both groups of mice developed increased HRP permeability during the experimental period, but at different times after inoculation: during the diarrheal period (days 2 and 3 pi) conventional mouse epithelium absorbed five times more HRP than noninfected controls and during the convalescence period (days 9 to 13 pi) HRP absorption in germ-free mice rose 10-fold as compared to its level before infection. In both cases, this increase in HRP permeability was entirely due to an increase in intact HRP absorption, probably via a transcellular route, and occurred without any alteration in degraded HRP transport. These results indicate that in mice, rotavirus infection causes a transient rise in gut permeability to undegraded proteins. The intestinal microflora seems to affect the timing, magnitude, and duration of this increased permeability
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