65 research outputs found
Calculation of the ultracold neutron upscattering loss probability in fluid walled storage bottles using experimental measurements of the thermomechanical properties of Fomblin
We present experimental measurements of the properties of a liquid "Fomblin"
surface obtained by the quasielastic scattering of laser light. The properties
include the surface tension and viscosity as a function of temperature. The
results are compared to the measurements of the bulk fluid properties.
We then calculate the upscattering rate of ultracold neutrons (UCN) from
thermally excited surface capillary waves on the liquid surface and compare the
results to experimental measurements of the UCN lifetime in Fomblin
fluid-walled UCN storage bottles, and show that the excess loss rate for UCN
energies near the Fomblin potential can be explained. The rapid temperature
dependence of the Fomblin storage lifetime is explained by our analysis.Comment: 25 pages, 13 figures; 2nd version corrects several error
Measurement of the neutron lifetime using a gravitational trap and a low-temperature Fomblin coating
We present a new value for the neutron lifetime of 878.5 +- 0.7 stat. +- 0.3
syst. This result differs from the world average value (885.7 +- 0.8 s) by 6.5
standard deviations and by 5.6 standard deviations from the previous most
precise result. However, this new value for the neutron lifetime together with
a beta-asymmetry in neutron decay, Ao, of -0.1189(7) is in a good agreement
with the Standard Model.Comment: 11 pages, 9 figures; extended content with some correction
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