570 research outputs found
The liquid helix
From everyday experience, we all know that a solid edge can deflect a liquid
flowing over it significantly, up to the point where the liquid completely
sticks to the solid. Although important in pouring, printing and extrusion
processes, there is no predictive model of this so-called "teapot effect". By
grazing vertical cylinders with inclined capillary liquid jets, we here use the
teapot effect to attach the jet to the solid and form a new structure: the
liquid helix. Using mass and momentum conservation along the liquid stream, we
first quantitatively predict the shape of the helix and then provide a
parameter-free inertial-capillary adhesion model for the jet deflection and
critical velocity for helix formation.Comment: Accepted in Physical Review Letters, author versio
The Highest Energy Neutrinos
Measurements of the arrival directions of cosmic rays have not revealed their
sources. High energy neutrino telescopes attempt to resolve the problem by
detecting neutrinos whose directions are not scrambled by magnetic fields. The
key issue is whether the neutrino flux produced in cosmic ray accelerators is
detectable. It is believed that the answer is affirmative, both for the
galactic and extragalactic sources, provided the detector has kilometer-scale
dimensions. We revisit the case for kilometer-scale neutrino detectors in a
model-independent way by focussing on the energetics of the sources. The real
breakthrough though has not been on the theory but on the technology front: the
considerable technical hurdles to build such detectors have been overcome.
Where extragalactic cosmic rays are concerned an alternative method to probe
the accelerators consists in studying the arrival directions of neutrinos
produced in interactions with the microwave background near the source, i.e.
within a GZK radius. Their flux is calculable within large ambiguities but, in
any case, low. It is therefore likely that detectors that are larger yet by
several orders of magnitudes are required. These exploit novel techniques, such
as detecting the secondary radiation at radio wavelengths emitted by neutrino
induced showers.Comment: 16 pages, pdflatex, 7 jpg figures, ICRC style files included.
Highlight talk presented at the 30th International Cosmic Ray Conference,
Merida, Mexico, 200
Tensor Analyzing Powers for Quasi-Elastic Electron Scattering from Deuterium
We report on a first measurement of tensor analyzing powers in quasi-elastic
electron-deuteron scattering at an average three-momentum transfer of 1.7
fm. Data sensitive to the spin-dependent nucleon density in the deuteron
were obtained for missing momenta up to 150 MeV/ with a tensor polarized
H target internal to an electron storage ring. The data are well described
by a calculation that includes the effects of final-state interaction,
meson-exchange and isobar currents, and leading-order relativistic
contributions.Comment: 4 pages, 3 figure
Point-Form Analysis of Elastic Deuteron Form Factors
Point-form relativistic quantum mechanics is applied to elastic
electron-deuteron scattering. The deuteron is modeled using relativistic
interactions that are scattering-equivalent to the nonrelativistic Argonne
and Reid '93 interactions. A point-form spectator approximation (PFSA)
is introduced to define a conserved covariant current in terms of
single-nucleon form factors. The PFSA is shown to provide an accurate
description of data up to momentum transfers of 0.5 , but falls
below the data at higher momentum transfers. Results are sensitive to the
nucleon form factor parameterization chosen, particularly to the neutron
electric form factor.Comment: RevTex, 31 pages, 1 table, 13 figure
Measurement of Tensor Polarization in Elastic Electron-Deuteron Scattering at Large Momentum Transfer
Tensor polarization observables (t20, t21 and t22) have been measured in
elastic electron-deuteron scattering for six values of momentum transfer
between 0.66 and 1.7 (GeV/c)^2. The experiment was performed at the Jefferson
Laboratory in Hall C using the electron HMS Spectrometer, a specially designed
deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new
data determine to much larger Q^2 the deuteron charge form factors G_C and G_Q.
They are in good agreement with relativistic calculations and disagree with
pQCD predictions.Comment: 5 pages, 4 figures, for associated informations, see
http://isnwww.in2p3.fr/hadrons/t20/t20_ang.html clarification about several
topics, one figure has been had, extraction of form factors use AQ
interpolation in our Q2 range onl
Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium
We report on a measurement of spin-momentum correlations in quasi-elastic
scattering of longitudinally polarized electrons with an energy of 720 MeV from
vector-polarized deuterium. The spin correlation parameter was
measured for the reaction for missing
momenta up to 350 MeV/ at a four-momentum transfer squared of 0.21
(GeV/c). The data give detailed information about the spin structure of the
deuteron, and are in good agreement with the predictions of microscopic
calculations based on realistic nucleon-nucleon potentials and including
various spin-dependent reaction mechanism effects. The experiment demonstrates
in a most direct manner the effects of the D-state in the deuteron ground-state
wave function and shows the importance of isobar configurations for this
reaction.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Lett. for publicatio
Measurements of electron-proton elastic cross sections for
We report on precision measurements of the elastic cross section for
electron-proton scattering performed in Hall C at Jefferson Lab. The
measurements were made at 28 unique kinematic settings covering a range in
momentum transfer of 0.4 5.5 . These measurements
represent a significant contribution to the world's cross section data set in
the range where a large discrepancy currently exists between the ratio of
electric to magnetic proton form factors extracted from previous cross section
measurements and that recently measured via polarization transfer in Hall A at
Jefferson Lab.Comment: 17 pages, 18 figures; text added, some figures replace
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