101 research outputs found
New Experimental Results on Strangeness Production
New experimental results on the production of and mesons
in the annihilation of stopped antiprotons are discussed. The explanation of
these facts in the framework of the polarized strangeness model is considered.Comment: 10 pages, Latex, fig1.eps, espcrc1.sty. Invited talk at the Low
Energy Antiproton Physics Conference, Villasimiu
Final State Interactions in
It is believed that the production rate of is almost
solely determined by final state interactions (FSI) and hence provides an ideal
place to test FSI models. Here we examine model calculations of the
contributions from s-channel resonance and t-channel exchange to
the FSI effects in . The contribution from s-channel
is sma The results from
two methods are roughly consistent with each other and can reproduce the large
rate of reasonably well$Comment: Latex, 16 pages, with 2 figure
decays with Final State Interactions
We study decays with final state interactions considered in
one-particle-exchange method. A clear physical picture for final state
interactions based on quark and hadronic level diagrams is presented. A strong
phase is introduced for hadronic effective couplings, which is crucial for
explaining the experimental data of , ,
and . Rescattering effects between different decay
channels are usually large. They are important for obtaining correct branching
ratios for decays in theoretical calculation.Comment: 14 Page, 8 figures, one table adde
Hadronic Probes of the Polarized Intrinsic Strangeness of the Nucleon
We have previously interpreted the various large apparent violations of the
naive Okubo-Zweig-Iizuka (OZI) rule found in many channels in
annihilation at LEAR as evidence for an intrinsic polarized
component of the nucleon wave function. The model is further supported by new
data from LEAR and elsewhere. Here we discuss in more detail the possible form
of the component of the nucleon wave function, interpret the new
data and clarify the relative roles of strangeness shake-out and rearrangement,
discuss whether alternative interpretations are still allowed by the new data,
and propose more tests of the model.Comment: LaTeX, 31 page
Measurements of the reaction of antiproton annihilation at rest at three hydrogen target densities
The proton-antiproton annihilation at rest into the final state
was measured for three different target densities: liquid hydrogen, gaseous
hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in
the liquid hydrogen target is smaller than in the low-pressure gas target. The
branching ratios of the channel were calculated on the basis of
simultaneous analysis of the three data samples. The branching ratio for
annihilation into from the protonium state turns out to be
about ten times smaller as compared to the one from the state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters
Nonfactorizable contributions in B decays to charmonium: the case of
Nonleptonic to charmonium decays generally show deviations from the
factorization predictions. For example, the mode has
been experimentally observed with sizeable branching fraction while its
factorized amplitude vanishes. We investigate the role of rescattering effects
mediated by intermediate charmed meson production in this class of decay modes,
and consider with the meson.
Using an effective lagrangian describing interactions of pairs of heavy-light
mesons with a quarkonium state, we relate this mode to the
analogous mode with in the final state. We find large enough to be measured at the factories, so that this decay
mode could be used to study the poorly known .Comment: RevTex, 16 pages, 2 eps figure
decay from charmed meson rescattering
We study the process considering intermediate charmed
meson rescattering effects. For this decay mode the naive factorization ansatz
would predict a vanishing amplitude. We estimate contributions from the
rescattering amplitudes, and compare the
result with recent experimental measurements. We find that rescattering effects
are able to produce a large branching ratio consistent with measurements by
Belle Collaboration. We also consider rescattering effects in , arguing that they play a similar role in producing a large branching
fraction for this colour-suppressed decay mode.Comment: LaTex, 13 pages, 2 eps figure
The antinucleon-nucleon interaction at low energy : annihilation dynamics
The general properties of antiproton-proton annihilation at rest are
presented, with special focus on the two-meson final states. The data exhibit
remarkable dynamical selection rules : some allowed annihilation modes are
suppressed by one order of magnitude with respect to modes of comparable
phase-space. Various phenomenological analyses are reviewed, based on
microscopic quark dynamics or symmetry considerations. The role of initial- and
final-state interaction is also examined.Comment: 128 pages, 49 tables, 27 figure
The Extrachromosomal EAST Protein of Drosophila Can Associate with Polytene Chromosomes and Regulate Gene Expression
The EAST protein of Drosophila is a component of an expandable extrachromosomal domain of the nucleus. To better understand its function, we studied the dynamics and localization of GFP-tagged EAST. In live larval salivary glands, EAST-GFP is highly mobile and localizes to the extrachromosomal nucleoplasm. When these cells are permeabilized, EAST-GFP rapidly associated with polytene chromosomes. The affinity to chromatin increases and mobility decreases with decreasing salt concentration. Deleting the C-terminal residues 1535 to 2301 of EAST strongly reduces the affinity to polytene chromosomes. The bulk of EAST-GFP co-localizes with heterochromatin and is absent from transcriptionally active chromosomal regions. The predominantly chromosomal localization of EAST-GFP can be detected in non-detergent treated salivary glands of pupae as they undergo apoptosis, however not in earlier stages of development. Consistent with this chromosomal pattern of localization, genetic evidence indicates a role for EAST in the repression of gene expression, since a lethal east mutation is allelic to the viable mutation suppressor of white-spotted. We propose that EAST acts as an ion sensor that modulates gene expression in response to changing intracellular ion concentrations
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