873 research outputs found
Probing Form Factors in Top Quark Pair Production at Colliders
We describe how to probe new physics through large CP violation effects and
non--standard Z-t-t couplings via the scattering process e^-e^+ -> t tbar.
[Talk presented at the Workshop on Physics and Experiments with Linear
Colliders, Waikoloa, Hawaii, 26-30 April 1993.]Comment: 4 pages, TeXsis, MSUTH 93/0
Electron tomography of late stages of FcRn-mediated antibody transcytosis in neonatal rat small intestine
The neonatal Fc receptor (FcRn) transports maternal immunoglobulin (IgG) across epithelia to confer passive immunity to mammalian young. In newborn rodents, FcRn transcytoses IgG from ingested milk across the intestinal epithelium for release into the bloodstream. We used electron tomography to examine FcRn transport of Nanogold-labeled Fc (Au-Fc) in neonatal rat jejunum, focusing on later aspects of transport by chasing Au-Fc before fixation. We observed pools of Au-Fc in dilated regions of the lateral intercellular space (LIS), likely representing exit sites where Au-Fc accumulates en route to the blood. Before weaning, the jejunum functions primarily in IgG transport and exhibits unusual properties: clathrin-rich regions near/at the basolateral LIS and multivesicular bodies (MVBs) expressing early endosomal markers. To address whether these features are related to IgG transport, we examined LIS and endocytic/transcytotic structures from neonatal and weaned animals. Weaned samples showed less LIS-associated clathrin. MVBs labeled with late endosomal/lysosomal markers were smaller than their neonatal counterparts but contained 10 times more internal compartments. These results are consistent with hypotheses that clathrin-rich basolateral regions in neonatal jejunum are involved in IgG exocytosis and that MVBs function in IgG transport while FcRn is expressed but switch to degradative functions after weaning, when the jejunum does not express FcRn or transport IgG
Production of Two Photons and a Jet Through Gluon Fusion
We have computed the cross-section and distributions for the production of two photons and a jet via the process . In the Standard Model, this process occurs at the one-loop level through pentagon and box diagrams. We show that at the LHC this is a significant mechanism for the production of the two photons and a jet. This process is also an important background to the Higgs boson production, when the Higgs boson decays into two photons. We also explorethis process at the Tevatron
Scalar Top Quark as the Next-to-Lightest Supersymmetric Particle
We study phenomenologically the scenario in which the scalar top quark is
lighter than any other standard supersymmetric partner and also lighter than
the top quark, so that it decays to the gravitino via stop -> W^+ b G. In this
case, scalar top quark events would seem to be very difficult to separate from
top quark pair production. However, we show that, even at a hadron collider, it
is possible to distinguish these two reactions. We show also that the
longitudinal polarization of the final gives insight into the scalar top
and wino/Higgsino mixing parameters.Comment: 18 pages, LaTeX, 7 figures, minor typographical correction
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