106 research outputs found
Computer Modeling of Displacement Cascades in Beryllium Irradiated with Intensive Neutron Flux
Photodissociation of p-process nuclei studied by bremsstrahlung induced activation
A research program has been started to study experimentally the
near-threshold photodissociation of nuclides in the chain of cosmic heavy
element production with bremsstrahlung from the ELBE accelerator. An important
prerequisite for such studies is good knowledge of the bremsstrahlung
distribution which was determined by measuring the photodissociation of the
deuteron and by comparison with model calculations. First data were obtained
for the astrophysically important target nucleus 92-Mo by observing the
radioactive decay of the nuclides produced by bremsstrahlung irradiation at
end-point energies between 11.8 MeV and 14.0 MeV. The results are compared to
recent statistical model calculations.Comment: 6 pages, 8 figures, Proceedings Nuclear Physics in Astrophysics II,
May 16-20, 2005, Debrecen, Hungary. The original publication is available at
www.eurphysj.or
Search for Doubly-Charged Higgs Boson Production at HERA
A search for the single production of doubly-charged Higgs bosons H^{\pm \pm}
in ep collisions is presented. The signal is searched for via the Higgs decays
into a high mass pair of same charge leptons, one of them being an electron.
The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment
at HERA. No evidence for doubly-charged Higgs production is observed and mass
dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs
boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only
decays into an electron and a muon via a coupling of electromagnetic strength
h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the
H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged
Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3,
masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl
Slowing down of relativistic few-electron heavy ions
Abstract Experimental data on energy loss and energy-loss straggling of fully ionized relativistic heavy ions agree well with the theory of Lindhard and Sùrensen (LS). However, when heavy ions penetrate matter with many¯uctuating ionic charge states the theoretical description is more complicate and less accurate. A novel exploratory step to contribute to a better understanding of the slowing down of heavy ions has been done with the present experiment in an energy region where the atomic interaction is still dominated by bare and few-electron projectiles. In the energy range of 100±1000 MeV/u we measured with the high-resolution magnetic spectrometer FRS the stopping powers, the energyloss straggling and the charge-state distributions of 197 Au, 208 Pb and 209 Bi projectiles in charge-state equilibrium interacting with solids ranging from beryllium to lead targets. Additionally, charge exchange cross-sections have been measured to support a better analysis and interpretation of the energy-loss data. The experimental results on stopping power and energy-loss straggling clearly demonstrate the contribution of ions in dierent charge states. A novel application of the slowing down of relativistic exotic heavy ions is presented.
Study of Charm Fragmentation into D^{*\pm} Mesons in Deep-Inelastic Scattering at HERA
The process of charm quark fragmentation is studied using meson
production in deep-inelastic scattering as measured by the H1 detector at HERA.
Two different regions of phase space are investigated defined by the presence
or absence of a jet containing the meson in the event. The
parameters of fragmentation functions are extracted for QCD models based on
leading order matrix elements and DGLAP or CCFM evolution of partons together
with string fragmentation and particle decays. Additionally, they are
determined for a next-to-leading order QCD calculation in the fixed flavour
number scheme using the independent fragmentation of charm quarks to
mesons.Comment: 33 pages, submitted to EPJ
Cross-section measurements for the and reactions
International audienceA neutron inelastic scattering experiment was performed on an enriched Fe57 sample at the Geel Electron Linear Accelerator neutron source using the Gamma Array for Neutron Inelastic Scattering spectrometer. Several γ-production cross sections were determined, but the first transition (14.4 keV) could not be detected owing to the steadily increased γ background at low energies. Consequently, we use an interplay between experimental data and carefully tuned theoretical calculations to generate the total inelastic cross section
Inelastic neutron scattering with GAINS at GELINA: An overview of the last decade
GAINS is an array of HPGe detectors installed at the GELINA neutron source of Joint Research Center, Geel, Belgium. It served to measure the cross section for (n,n’γ) reactions on many isotopes. The paper presents the experimental setup and reviews the main results obtained in the last decade.JRC.G.2-Standards for Nuclear Safety, Security and Safeguard
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