16,555 research outputs found
Restraining mechanism
A restraining mechanism restraining a pressurized garment so as to limit its ballooning effect is described. A helically wound spring is bonded at its outer periphery to an elongated flat plate which permits the flat plate to bend in a single direction. The flat plate is attached to an inflatable glove to the palm side for restraining the glove from ballooning when inflated
Superallowed Fermi beta decay and Coulomb mixing in nuclei
Superallowed nuclear beta decay provides a direct measure of
the weak vector coupling constant, \GV. We survey current world data on the
nine accurately determined transitions of this type, which range from the decay
of C to that of Co, and demonstrate that the results confirm
conservation of the weak vector current (CVC) but differ at the 98% confidence
level from the unitarity condition for the Cabibbo-Kobayashi-Maskawa (CKM)
matrix. We examine the reliability of the small calculated corrections that
have been applied to the data, and conclude that there are no evident defects
although the Coulomb correction, , depends sensitively on nuclear
structure and thus needs to be constrained independently. The potential
importance of a result in disagreement with unitarity, clearly indicates the
need for further work to confirm or deny the discrepancy. We examine the
options and recommend priorities for new experiments and improved calculations.
Some of the required experiments depend upon the availability of intense
radioactive beams. Others are possible with existing facilities.Comment: 12 pages, LaTeX with aipproc2.sty (included) and epsf.sty; Invited
talk at Nuclear Structure 98, Gatlinburg, Tennessee, Aug. 199
CURRENTS AND THEIR COUPLINGS IN THE WEAK SECTOR OF THE STANDARD MODEL
Beta-decay and muon-capture experiments in nuclei are reviewed. The conserved
vector current hypothesis is confirmed through the observed constancy of the
vector coupling constant determined from the superallowed Fermi transitions and
from the measurement of the weak-magnetism term in mirror Gamow-Teller
transitions. The axial-vector and pseudoscalar coupling constants in the
nucleon are determined from neutron decay and muon capture on the proton
respectively. In finite nuclei, evidence for these coupling constants being
reduced relative to their free-nucleon values is discussed. Meson-exchange
currents are shown to be an important correction to the time-like part of the
axial current as evident in first-forbidden beta decays. Tests of the Standard
Model are discussed, as well as extensions beyond it involving right-hand
currents and scalar interactions.Comment: 67 pages, plain LaTex, uses worldsci.sty, two figures embedded in
manuscript as tex statements. A chapter for a book entitled 'The Nucleus as a
Laboratory for Studying Symmetries and Fundamental Interactions', eds. E.M.
Henley and W.C. Haxto
New limit on fundamental weak-interaction parameters from superallowed beta decay
A new critical survey of all world data on superallowed beta decays provides
demanding tests of, and tight constraints on, the weak interaction. In
confirmation of the conserved vector current (CVC) hypothesis, the vector
coupling coupling constant is demonstrated to be constant to better than 3
parts in 10^4, and any induced scalar current is limited to fs \leq 0.0013 in
electron rest-mass units. The possible existence of a fundamental scalar
current is similarly limited to |Cs/Cv| \leq 0.0013. The superallowed data also
determine the CKM matrix element to be Vud = 0.9738(4). With PDG values for Vus
and Vub, the top-row test of CKM unitarity yields Vud^2 + Vus^2 + Vub^2 =
0.9966(14); although, if a recent result on Ke3 decay is used exclusively to
obtain Vus, this sum becomes 0.9999(16). Limits on possible right-hand currents
are given.Comment: 4 pages, one postscript fil
Rotary antenna attenuator
Radio frequency attenuator, having negligible insertion loss at minimum attenuation, can be used for making precise antenna gain measurements. It is small in size compared to a rotary-vane attenuator
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