7,562 research outputs found
Tools made of ice facilitate forming of soft, sticky materials
Tools made of ice facilitate the forming or shaping of materials that are soft and sticky in the uncured state. The low-temperature of the ice slows the curing of the material, extending the working time available before setup. Handling problems are eliminated because the material does not adhere to the tool, and the melting ice serves as a lubricant
Charged Current Universality and the MSSM
We analyze the prospective impact of supersymmetric radiative corrections on
tests of charged current universality involving light quarks and leptons.
Working within the R-parity conserving Minimal Supersymmetric Standard Model,
we compute the corresponding one-loop corrections that enter the extraction of
the Cabibbo-Kobayashi-Maskawa matrix element from a comparison of the
muon-decay Fermi constant with the vector coupling constant determined from
nuclear and neutron -decay. We also revisit earlier studies of the
corrections to the ratio of pion leptonic decay rates and . In both
cases, we observe that the magnitude of the corrections can be on the order of
. We show that a comparison of the first row CKM unitarity tests with
measurements of can provide unique probes of the spectrum of first
generation squarks and first and second generation sleptons.Comment: 38 pages, 17 figure
Pilot cryo tunnel: Attachments, seals, and insulation
Several different tests are described which simulated the actual configuration of a cryogenic wind tunnel operating at pressures up to 5 atmospheres (507 kPa) and temperatures from -320 F (78K) to 120 F (322K) in order to determine compatible bolting, adequate sealing, and effective insulating materials. The evaluation of flange attachments (continuous threaded studs) considered bolting based on compatible flanges, attachment materials, and prescribed bolt elongations. Various types of seals and seal configurations were studied to determine suitability and reusability under the imposed pressure and temperature loadings. The temperature profile was established for several materials used for structural supports
Pion Leptonic Decays and Supersymmetry
We compute supersymmetric contributions to pion leptonic (\pi_{l2}) decays in
the Minimal Supersymmetric Standard Model (MSSM). When R-parity is conserved,
the largest contributions to the ratio R_{e/\mu} = \Gamma[ \pi^+ \to e^+
\nu_e(\gamma)]/\Gamma[ \pi^+ \to \mu^+ \nu_\mu(\gamma)] arise from one-loop
(V-A)x(V-A) corrections. These contributions can be potentially as large as the
sensitivities of upcoming experiments; if measured, they would imply
significant bounds on the chargino and slepton sectors complementary to current
collider limits. We also analyze R-parity violating interactions, which may
produce a detectable deviation in R_{e/\mu} while remaining consistent with all
other precision observables.Comment: 12 pages, 11 figures; included additional electroweak constraints in
analysis, simplified abstract, ref. adde
A double-helix neutron detector using micron-size B-10 powder
A double-helix electrode configuration is combined with a B powder
coating technique to build large-area (9 in 36 in) neutron detectors.
The neutron detection efficiency for each of the four prototypes is comparable
to a single 2-bar He drift tube of the same length (36 in). One unit has
been operational continuously for 18 months and the change of efficiency is
less than 1%. An analytic model for pulse heigh spectra is described and the
predicted mean film thickness agrees with the experiment to within 30%. Further
detector optimization is possible through film texture, power size, moderator
box and gas. The estimated production cost per unit is less than 3k US\$ and
the technology is thus suitable for deployment in large numbers
Hadron Spin Dynamics
Spin effects in exclusive and inclusive reactions provide an essential new
dimension for testing QCD and unraveling hadron structure. Remarkable new
experiments from SLAC, HERMES (DESY), and the Jefferson Laboratory present many
challenges to theory, including measurements at HERMES and SMC of the single
spin asymmetries in pion electroproduction, where the proton is polarized
normal to the scattering plane. This type of single spin asymmetry may be due
to the effects of rescattering of the outgoing quark on the spectators of the
target proton, an effect usually neglected in conventional QCD analyses. Many
aspects of spin, such as single-spin asymmetries and baryon magnetic moments
are sensitive to the dynamics of hadrons at the amplitude level, rather than
probability distributions. I illustrate the novel features of spin dynamics for
relativistic systems by examining the explicit form of the light-front
wavefunctions for the two-particle Fock state of the electron in QED, thus
connecting the Schwinger anomalous magnetic moment to the spin and orbital
momentum carried by its Fock state constituents and providing a transparent
basis for understanding the structure of relativistic composite systems and
their matrix elements in hadronic physics. I also present a survey of
outstanding spin puzzles in QCD, particularly the double transverse spin
asymmetry A_{NN} in elastic proton-proton scattering, the J/psi to rho-pi
puzzle, and J/psi polarization at the Tevatron.Comment: Concluding theory talk presented at SPIN2001, the Third
Circum-Pan-Pacific Symposium on High Energy Physics, October, 2001, Beijin
Loading of a surface-electrode ion trap from a remote, precooled source
We demonstrate loading of ions into a surface-electrode trap (SET) from a
remote, laser-cooled source of neutral atoms. We first cool and load
neutral Sr atoms into a magneto-optical trap from an oven that
has no line of sight with the SET. The cold atoms are then pushed with a
resonant laser into the trap region where they are subsequently photoionized
and trapped in an SET operated at a cryogenic temperature of 4.6 K. We present
studies of the loading process and show that our technique achieves ion loading
into a shallow (15 meV depth) trap at rates as high as 125 ions/s while
drastically reducing the amount of metal deposition on the trap surface as
compared with direct loading from a hot vapor. Furthermore, we note that due to
multiple stages of isotopic filtering in our loading process, this technique
has the potential for enhanced isotopic selectivity over other loading methods.
Rapid loading from a clean, isotopically pure, and precooled source may enable
scalable quantum information processing with trapped ions in large, low-depth
surface trap arrays that are not amenable to loading from a hot atomic beam
Stability of atomic clocks based on entangled atoms
We analyze the effect of realistic noise sources for an atomic clock
consisting of a local oscillator that is actively locked to a spin-squeezed
(entangled) ensemble of atoms. We show that the use of entangled states can
lead to an improvement of the long-term stability of the clock when the
measurement is limited by decoherence associated with instability of the local
oscillator combined with fluctuations in the atomic ensemble's Bloch vector.
Atomic states with a moderate degree of entanglement yield the maximal clock
stability, resulting in an improvement that scales as compared to the
atomic shot noise level.Comment: 4 pages, 2 figures, revtex
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