1,499 research outputs found
Electromagnetic Calorimeter for HADES
We propose to build the Electromagnetic calorimeter for the HADES di-lepton
spectrometer. It will enable to measure the data on neutral meson production
from nucleus-nucleus collisions, which are essential for interpretation of
dilepton data, but are unknown in the energy range of planned experiments (2-10
GeV per nucleon). The calorimeter will improve the electron-hadron separation,
and will be used for detection of photons from strange resonances in elementary
and HI reactions.
Detailed description of the detector layout, the support structure, the
electronic readout and its performance studied via Monte Carlo simulations and
series of dedicated test experiments is presented.
The device will cover the total area of about 8 m^2 at polar angles between
12 and 45 degrees with almost full azimuthal coverage. The photon and electron
energy resolution achieved in test experiments amounts to 5-6%/sqrt(E[GeV])
which is sufficient for the eta meson reconstruction with S/B ratio of 0.4% in
Ni+Ni collisions at 8 AGeV. A purity of the identified leptons after the hadron
rejection, resulting from simulations based on the test measurements, is better
than 80% at momenta above 500 MeV/c, where time-of-flight cannot be used.Comment: 40 pages, 38 figures version2 - the time schedule added, information
about PMTs in Sec.III update
CASTOR: Centauro and Strange Object Research in nucleus-nucleus collisions at LHC
We describe the CASTOR detector designed to probe the very forward,
baryon-rich rapidity region in nucleus-nucleus collisions at the LHC. We
present a phenomenological model describing the formation of a QGP fireball in
a high baryochemical potential environment, and its subsequent decay into
baryons and strangelets. The model explains Centauros and the long-penetrating
component and makes predictions for the LHC.
Simulations of Centauro-type events were done. To study the response of the
apparatus to new effects different exotic species (DCC, Centauros, strangelets
etc.) were passed through the deep calorimeter. The energy deposition pattern
in the calorimeter appears to be a new clear signature of the QGP.Comment: Talk given by E. Gladysz-Dziadus for the CASTOR group, Intern.
Workshop on Nuclear Theory, 10-15 June, 2002, Bulgaria, Rila Mountains, 15
pages, 14 figure
Non-Statistical Effects in Neutron Capture
There have been many reports of non-statistical effects in neutron-capture
measurements. However, reports of deviations of reduced-neutron-width
distributions from the expected Porter-Thomas (PT) shape largely have been
ignored. Most of these deviations have been reported for odd-A nuclides.
Because reliable spin (J) assignments have been absent for most resonances for
such nuclides, it is possible that reported deviations from PT might be due to
incorrect J assignments. We recently developed a new method for measuring spins
of neutron resonances by using the DANCE detector at LANSCE. Measurements made
with a 147Sm sample allowed us to determine spins of almost all known
resonances below 1 keV. Furthermore, analysis of these data revealed that the
reduced-neutron-width distribution was in good agreement with PT for resonances
below 350 eV, but in disagreement with PT for resonances between 350 and 700
eV. Our previous (n,alpha) measurements had revealed that the alpha strength
function also changes abruptly at this energy. There currently is no known
explanation for these two non-statistical effects. Recently, we have developed
another new method for determining the spins of neutron resonances. To
implement this technique required a small change (to record pulse-height
information for coincidence events) to a much simpler apparatus: A pair of C6D6
gamma-ray detectors which we have employed for many years to measure
neutron-capture cross sections at ORELA. Measurements with a 95Mo sample
revealed that not only does the method work very well for determining spins,
but it also makes possible parity assignments. Taken together, these new
techniques at LANSCE and ORELA could be very useful for further elucidation of
non-statistical effects.Comment: 8 pages, 3 figures, for proceedings of CGS1
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