2,792 research outputs found
Cosmic ray tests of a GEM-based TPC prototype operated in Ar-CF4-isobutane gas mixtures
Argon with an admixture of CF4 is expected to be a good candidate for the gas
mixture to be used for a time projection chamber (TPC) in the future linear
collider experiment because of its small transverse diffusion of drift
electrons especially under a strong magnetic field. In order to confirm the
superiority of this gas mixture over conventional TPC gases we carried out
cosmic ray tests using a GEM-based TPC operated mostly in Ar-CF4-isobutane
mixtures under 0 - 1 T axial magnetic fields. The measured gas properties such
as gas gain and transverse diffusion constant as well as the observed spatial
resolution are presented.Comment: 22 pages, 18 figures. Published in Nuclear Instruments and Methods in
Physics Research A. Fig. 3 in the introduction was corrected since it had not
been properly normalized. Minor corrections and no changes in the conclusio
Zeno dynamics yields ordinary constraints
The dynamics of a quantum system undergoing frequent measurements (quantum
Zeno effect) is investigated. Using asymptotic analysis, the system is found to
evolve unitarily in a proper subspace of the total Hilbert space. For spatial
projections, the generator of the "Zeno dynamics" is the Hamiltonian with
Dirichlet boundary conditions.Comment: 6 page
Spallation Neutron Production by 0.8, 1.2 and 1.6 GeV Protons on various Targets
Spallation neutron production in proton induced reactions on Al, Fe, Zr, W,
Pb and Th targets at 1.2 GeV and on Fe and Pb at 0.8, and 1.6 GeV measured at
the SATURNE accelerator in Saclay is reported. The experimental
double-differential cross-sections are compared with calculations performed
with different intra-nuclear cascade models implemented in high energy
transport codes. The broad angular coverage also allowed the determination of
average neutron multiplicities above 2 MeV. Deficiencies in some of the models
commonly used for applications are pointed out.Comment: 20 pages, 32 figures, revised version, accepted fpr publication in
Phys. Rev.
Experimental limits on massive neutrinos from e(+)e(-) annihilations at 29 GeV
This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.37.577.A search was made in 29-GeV e(+)e(-) annihilations for massive neutrinos decaying to e(±)X(â)(Îœ) where X is a muon or meson. A 300-pb(-1) data sample yielded just one candidate event with a mass m(e)X>1.8 GeV. Significant limits are found for new neutrinos with masses from 1.8 to 6.7 GeV and with mixing parameters in the range 3Ă10(-6)<âUâ(2)<1. .A
Reflection and Transmission in a Neutron-Spin Test of the Quantum Zeno Effect
The dynamics of a quantum system undergoing frequent "measurements", leading
to the so-called quantum Zeno effect, is examined on the basis of a
neutron-spin experiment recently proposed for its demonstration. When the
spatial degrees of freedom are duely taken into account, neutron-reflection
effects become very important and may lead to an evolution which is totally
different from the ideal case.Comment: 26 pages, 6 figure
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