729 research outputs found
Photoexcitation of baryon resonances on nucleons and nuclei: An example: recent results from photoproduction of η -mesons
Abstract.: Photoproduction of η-mesons off the proton, the deuteron and other light nuclei, and off heavy nuclei has been studied in detail during the last decade at the electron accelerators MAMI in Mainz, ELSA in Bonn, ERSF in Grenoble, CEBAF in Newport News, at KEK, and at Tohoku. The physics topics range from the detailed investigation of the properties of known nucleon resonances (in particular S 11(1535)), over the search of new states, to the in-medium properties of baryon resonances, and the possible formation of η-nucleus (quasi)bound states (η-mesic nuclei). It is thus an excellent example for the different aspects of the photoexcitation of nucleon resonances. Here we report new preliminary results from the CBELSA/TAPS experiment for this reaction at higher incident photon energies for the deuteron and heavy nucle
Simulation of the Directional Dark Matter Detector (D3) and Directional Neutron Observer (DiNO)
Preliminary simulation and optimization studies of the Directional Dark
Matter Detector and the Directional Neutron Observer are presented. These
studies show that the neutron interaction with the gas-target in these
detectors is treated correctly by GEANT4 and that by lowering the pressure, the
sensitivity to low-mass WIMP candidates is increased. The use of negative ion
drift might allow us to search the WIMP mass region suggested by the results of
the non-directional experiments DAMA/LIBRA, CoGeNT and CRESST-II.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
K*-couplings for the antidecuplet excitation
We estimate the coupling of the K* vector meson to the N-->Theta+ transition
employing unitary symmetry, vector meson dominance, and results from the GRAAL
Collaboration for eta photoproduction off the neutron. Our small numerical
value for the coupling constant is consistent with the non-observation of the
Theta+ in recent CLAS searches for its photoproduction. We also estimate the
K*-coupling for the N-->Sigma* excitation, with Sigma* being the Sigma-like
antidecuplet partner of the Theta+-baryon.Comment: 9 pages, 1 figure. Minor changes in text and abstract, references
added; version to appear in Phys. Rev.
Sources and budgets for CO and O-3 in the northeastern Pacific during the spring of 2001: Results from the PHOBEA-II Experiment
Abstract. Ground and airborne measurements of CO, ozone, and aerosols were obtained in th
Photoproduction of mesons off neutrons from a deuteron target
A formalism is developed for the partial wave analysis of data on meson
photoproduction off deuterons and applied to photoproduction of and
mesons. Different interpretations of a dip-bump structure of the
photoproduction cross section in the 1670 MeV region are presented and
discussed. Helicity amplitudes for two low-mass states are determined.Comment: 11 pages, 13 figure
Charge-Focusing Readout of Time Projection Chambers
Time projection chambers (TPCs) have found a wide range of applications in
particle physics, nuclear physics, and homeland security. For TPCs with
high-resolution readout, the readout electronics often dominate the price of
the final detector. We have developed a novel method which could be used to
build large-scale detectors while limiting the necessary readout area. By
focusing the drift charge with static electric fields, we would allow a small
area of electronics to be sensitive to particle detection for a much larger
detector volume. The resulting cost reduction could be important in areas of
research which demand large-scale detectors, including dark matter searches and
detection of special nuclear material. We present simulations made using the
software package Garfield of a focusing structure to be used with a prototype
TPC with pixel readout. This design should enable significant focusing while
retaining directional sensitivity to incoming particles. We also present first
experimental results and compare them with simulation.Comment: 5 pages, 17 figures, Presented at IEEE Nuclear Science Symposium 201
The Directional Dark Matter Detector
Gas-filled Time Projection Chambers (TPCs) with Gas Electron Multipliers
(GEMs) and pixels appear suitable for direction-sensitive WIMP dark matter
searches. We present the background and motivation for our work on this
technology, past and ongoing prototype work, and a development path towards an
affordable, 1--scale directional dark matter detector, \dcube. Such a
detector may be particularly suitable for low-mass WIMP searches, and perhaps
sufficiently sensitive to clearly determine whether the signals seen by DAMA,
CoGeNT, and CRESST-II are due to low-mass WIMPs or background.Comment: Proceedings of the 3rd International conference on Directional
Detection of Dark Matter (CYGNUS 2011), Aussois, France, 8-10 June 201
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