476 research outputs found
A prototype for the AMS-RICH experiment
The AMS spectrometer will be installed on the International Space Station in
2005. Among other improvements over the first version of the instrument, a ring
imaging Cherenkov detector (RICH) will be added and should open a new window
for cosmic-ray physics, allowing isotope separation up to A = 25 between 1 and
10 GeV/c and element identification up to Z = 25 between threshold and 1
TeV/c/nucleon. It should also contribute to the high level of redundancy
required for AMS and reject efficiency albedo particles. A second generation
prototype has been operated for a few months : the architecture and the first
results are presented.Comment: Proceedings of the 3rd International Conference on "New developments
in photodetection" (Beaune - France
Variation of the Diameter of the Sun as Measured by the Solar Disk Sextant (SDS)
The balloon-borne Solar Disk Sextant (SDS) experiment has measured the
angular size of the Sun on seven occasions spanning the years 1992 to 2011. The
solar half-diameter -- observed in a 100-nm wide passband centred at 615 nm --
is found to vary over that period by up to 200 mas, while the typical estimated
uncertainty of each measure is 20 mas. The diameter variation is not in phase
with the solar activity cycle; thus, the measured diameter variation cannot be
explained as an observational artefact of surface activity. Other possible
instrument-related explanations for the observed variation are considered but
found unlikely, leading us to conclude that the variation is real. The SDS is
described here in detail, as is the complete analysis procedure necessary to
calibrate the instrument and allow comparison of diameter measures across
decades.Comment: 41 pages; appendix and 2 figures added plus some changes in text
based on referee's comments; to appear in MNRA
A RICH prototype for the AMS experiment
The AMS spectrometer will be installed on the International Space Station at
the end of 2003. Among other improvements over the first version of the
instrument, a ring imaging Cherenkov detector (RICH) will be added which latter
should open a new window for cosmic-ray physics, allowing isotope separation up
to A~25 between 1 and 10 GeV/c and elements identification up to Z~25 between
threshold and 1 TeV/c/nucleon. It should also contribute to the high level of
redundancy required for AMS and reject efficiency albedo particles. The results
of the first generation prototype and the expected results of the new one are
discussed.Comment: 4 pages, 6 figures, ICRC proceeding
Three-manifold invariant from functional integration
We give a precise definition and produce a path-integral computation of the
normalized partition function of the abelian U(1) Chern-Simons field theory
defined in a general closed oriented 3-manifold. We use the Deligne-Beilinson
formalism, we sum over the inequivalent U(1) principal bundles over the
manifold and, for each bundle, we integrate over the gauge orbits of the
associated connection 1- forms. The result of the functional integration is
compared with the abelian U(1) Reshetikhin-Turaev surgery invariant
Abelian BF theory and Turaev-Viro invariant
The U(1) BF Quantum Field Theory is revisited in the light of
Deligne-Beilinson Cohomology. We show how the U(1) Chern-Simons partition
function is related to the BF one and how the latter on its turn coincides with
an abelian Turaev-Viro invariant. Significant differences compared to the
non-abelian case are highlighted.Comment: 47 pages and 6 figure
Higher dimensional abelian Chern-Simons theories and their link invariants
The role played by Deligne-Beilinson cohomology in establishing the relation
between Chern-Simons theory and link invariants in dimensions higher than three
is investigated. Deligne-Beilinson cohomology classes provide a natural abelian
Chern-Simons action, non trivial only in dimensions , whose parameter
is quantized. The generalized Wilson -loops are observables of the
theory and their charges are quantized. The Chern-Simons action is then used to
compute invariants for links of -loops, first on closed
-manifolds through a novel geometric computation, then on
through an unconventional field theoretic computation.Comment: 40 page
Experimental study of a proximity focusing Cherenkov counter prototype for the AMS experiment
A study prototype of Proximity Focussing Ring Imaging Cherenkov counter has
been built and tested with several radiators using separately cosmic-ray
particles and 12C beam fragmentation products at several energies. Counter
prototype and experimental setup are described, and the results of measurements
reported and compared with simulation results.The performances are discussed in
the perspective of the final counter design.Comment: 27 pages, 16 figures, submitted to NIM
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