6,625 research outputs found
Prospects for measuring the 229Th isomer energy using a metallic magnetic microcalorimeter
The Thorium-229 isotope features a nuclear isomer state with an extremely low
energy. The currently most accepted energy value, 7.8 +- 0.5 eV, was obtained
from an indirect measurement using a NASA x-ray microcalorimeter with an
instrumental resolution 26 eV. We study, how state-of-the-art magnetic metallic
microcalorimeters with an energy resolution down to a few eV can be used to
measure the isomer energy. In particular, resolving the 29.18 keV doublet in
the \gamma-spectrum following the \alpha-decay of Uranium-233, corresponding to
the decay into the ground and isomer state, allows to measure the isomer
transition energy without additional theoretical input parameters, and increase
the energy accuracy. We study the possibility of resolving the 29.18 keV line
as a doublet and the dependence of the attainable precision of the energy
measurement on the signal and background count rates and the instrumental
resolution.Comment: 32 pages, 8 figures, eq. (3) correcte
Hadron multiplicities in e+e- annihilation with heavy primary quarks
The multiple hadron production in the events induced by the heavy primary
quarks in annihilation is reconsidered with account of corrected
experimental data. New value for the multiplicity in events is
presented on the basis of pQCD estimates.Comment: 16 pages, 6 figures. Version accepted for publication in EPJ
Spin flip lifetimes in superconducting atom chips: BCS versus Eliashberg theory
We investigate theoretically the magnetic spin-flip transitions of neutral
atoms trapped near a superconducting slab. Our calculations are based on a
quantum-theoretical treatment of electromagnetic radiation near dielectric and
metallic bodies. Specific results are given for rubidium atoms near a niobium
superconductor. At the low frequencies typical of the atomic transitions, we
find that BCS theory greatly overestimates coherence effects, which are much
less pronounced when quasiparticle lifetime effects are included through
Eliashberg theory. At 4.2 K, the typical atomic spin lifetime is found to be
larger than a thousand seconds, even for atom-superconductor distances of one
micrometer. This constitutes a large enhancement in comparison with normal
metals.Comment: 10 pages, 4 figure
Calibration of a single atom detector for atomic micro chips
We experimentally investigate a scheme for detecting single atoms
magnetically trapped on an atom chip. The detector is based on the
photoionization of atoms and the subsequent detection of the generated ions. We
describe the characterization of the ion detector with emphasis on its
calibration via the correlation of ions with simultaneously generated
electrons. A detection efficiency of 47.8% (+-2.6%) is measured, which is
useful for single atom detection, and close to the limit allowing atom counting
with sub-Poissonian uncertainty
Report of the Subgroup on Alternative Models and New Ideas
We summarize some of the work done by the P3 subgroup on Alternative Models
and New Ideas. The working group covered a broad range of topics including a
constrained Standard Model from an extra dimension, a discussion of recent
ideas addressing the strong CP problem, searches for doubly charged higgs
bosons in e gamma collisions, and an update on discovery limits for extra
neutral gauge bosons at hadron colliders. The breadth of topics reflects the
many ideas and approaches to physics beyond the Standard Model.Comment: 10 pages, 5 figures. Contributed to the APS/DPF/DPB Summer Study on
the Future of Particle Physics (Snowmass 2001), Snowmass, Colorado, 30 Jun -
21 Jul 200
Performance of a 229 Thorium solid-state nuclear clock
The 7.8 eV nuclear isomer transition in 229 Thorium has been suggested as an
etalon transition in a new type of optical frequency standard. Here we discuss
the construction of a "solid-state nuclear clock" from Thorium nuclei implanted
into single crystals transparent in the vacuum ultraviolet range. We
investigate crystal-induced line shifts and broadening effects for the specific
system of Calcium fluoride. At liquid Nitrogen temperatures, the clock
performance will be limited by decoherence due to magnetic coupling of the
Thorium nucleus to neighboring nuclear moments, ruling out the commonly used
Rabi or Ramsey interrogation schemes. We propose a clock stabilization based on
counting of flourescence photons and present optimized operation parameters.
Taking advantage of the high number of quantum oscillators under continuous
interrogation, a fractional instability level of 10^{-19} might be reached
within the solid-state approach.Comment: 28 pages, 9 figure
Common Stink Bugs of Utah
This fact sheet provides information of some of Utah\u27s commonly encountered stink bugs, including what they look like, where to find them, and other key identifying characteristics
Multiple hadron production in e+e- annihilation induced by heavy primary quarks. New analysis
In this paper we present an analysis of the multiple hadron production
induced by primary heavy quarks in e+e- annihilation with the account of most
complete and corrected experimental data. In the framework of perturbative QCD,
new theoretical bounds on the asymptotically constant differences of the
multiplicities in processes with light and heavy quarks are given.Comment: 26 pages, 7 figures, to be published in Particles & Nucle
- âŠ