2,979 research outputs found
Solving the Solar Neutrino Problem 2 km Underground -- the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) is capable of measuring simultaneously
the flux of electron-type neutrinos and the total flux of all active flavours
of neutrinos originating from the Sun. A model-independent test of neutrino
flavour transformation was performed by comparing these two measurements.
Assuming an undistorted neutrino energy spectrum, this transformation has been
definitively demonstrated in the pure D2O phase of the SNO experiment. In the
second phase with dissolved NaCl in the D2O, the total active solar neutrino
flux was measured without any assumption on the energy dependence of flavour
transformation. In this talk, results from these measurements, their physics
implications and the current status of the SNO experiment are presented.Comment: Proceedings of the 8th ICATPP Conference on Astroparticle, Particle,
Space Physics, Detectors and Medical Physics Applications (Como, Italy, Oct
6-10, 2003) 10 pages, 3 figures, 2 table
Recent Results from the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) measures both the flux of the
electron-type neutrinos and the total flux of all active flavours of neutrinos
originating from the Sun. A model-independent test of neutrino flavour
transformation was performed by comparing these two measurements. In 2002, this
flavour transformation was definitively demonstrated. In this talk, results
from these measurements and the current status of the SNO detector are
presented.Comment: Proceedings of the International Europhysics Conference on High
Energy Physics (EPS2003) 3 pages, 2 figures, 2 table
Solar Neutrino Observations at the Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory (SNO) is a 1000-tonne heavy water Cherenkov
detector. Its usage of \dto as target allows the simultaneous measurements of
the flux from B decay in the Sun and the total flux of all active
neutrino species through the charged-current and the neutral-current
interactions on the deuterons. Assuming the standard B shape, the
component of the B solar neutrino flux is measured to be for a kinetic energy threshold of 5 MeV. The non-\nue component
is found to be \phinumutau = 3.41^{+0.45}_{-0.45}{(stat.)}^{+0.48}_{-0.45}
{(syst.)} x 10^6 {\rm cm}^{-2} {\rm s}^{-1}. This difference
provides strong evidence for flavor transformation in the solar
neutrino sector. The total active neutrino flux is measured with the
neutral-current reaction at a neutrino energy threshold of 2.2 MeV. This flux
is determined to be , and is consistent with solar
model predictions. Assuming an undistorted B spectrum, the night minus day
rate is 14.06.3(stat.)(sys.)\% of the average rate in the
charged-current channel. If the total active neutrino flux is constrained to
have no asymmetry, the night-day asymmetry in the flux is found to be
7.04.9(stat.)(sys.)\%. A global analysis of all the
available solar neutrino data in terms of matter-enhanced oscillations of two
active flavors strongly favors the Large Mixing Angle (LMA) solution.Comment: invited talk at the SLAC Summer Institute Topical Conference
(SSI02-TTh01), 2002, 43 pages, 19 figures, 10 table
Low-background temperature sensors fabricated on parylene substrates
Temperature sensors fabricated from ultra-low radioactivity materials have
been developed for low-background experiments searching for neutrinoless
double-beta decay and the interactions of WIMP dark matter. The sensors consist
of electrical traces photolithographically-patterned onto substrates of
vapor-deposited parylene. They are demonstrated to function as expected, to do
so reliably and robustly, and to be highly radio-pure. This work is a
proof-of-concept study of a technology that can be applied to broad class of
electronic circuits used in low-background experiments
Distribution of the second virial coefficients of globular proteins
George and Wilson [Acta. Cryst. D 50, 361 (1994)] looked at the distribution
of values of the second virial coefficient of globular proteins, under the
conditions at which they crystallise. They found the values to lie within a
fairly narrow range. We have defined a simple model of a generic globular
protein. We then generate a set of proteins by picking values for the
parameters of the model from a probability distribution. At fixed solubility,
this set of proteins is found to have values of the second virial coefficient
that fall within a fairly narrow range. The shape of the probability
distribution of the second virial coefficient is Gaussian because the second
virial coefficient is a sum of contributions from different patches on the
protein surface.Comment: 5 pages, including 3 figure
Potential one-forms for hyperk\"ahler structures with torsion
It is shown that an HKT-space with closed parallel potential 1-form has
-symmetry. Every locally conformally hyperk\"ahler manifold
generates this type of geometry. The HKT-spaces with closed parallel potential
1-form arising in this way are characterized by their symmetries and an
inhomogeneous cubic condition on their torsion.Comment: 16 pages, Latex, no figure
Gel transitions in colloidal suspensions
The idealized mode coupling theory (MCT) is applied to colloidal systems
interacting via short-range attractive interactions of Yukawa form. At low
temperatures MCT predicts a slowing down of the local dynamics and ergodicity
breaking transitions. The nonergodicity transitions share many features with
the colloidal gel transition, and are proposed to be the source of gelation in
colloidal systems. Previous calculations of the phase diagram are complemented
with additional data for shorter ranges of the attractive interaction, showing
that the path of the nonergodicity transition line is then unimpeded by the
gas-liquid critical curve at low temperatures. Particular attention is given to
the critical nonergodicity parameters, motivated by recent experimental
measurements. An asymptotic model is developed, valid for dilute systems of
spheres interacting via strong short-range attractions, and is shown to capture
all aspects of the low temperature MCT nonergodicity transitions.Comment: 12 pages, LaTeX, 5 eps figures, uses ioplppt.sty, to appear in J.
Phys.: Condens. Matte
Colloidal gelation and non-ergodicity transitions
Within the framework of the mode coupling theory (MCT) of structural
relaxation, mechanisms and properties of non-ergodicity transitions in rather
dilute suspensions of colloidal particles characterized by strong short-ranged
attractions are studied. Results building on the virial expansion for particles
with hard cores and interacting via an attractive square well potential are
presented, and their relevance to colloidal gelation is discussed.Comment: 10 pages, 4 figures; Talk at the Conference: "Unifying Concepts in
Glass Physics" ICTP Trieste, September 1999; to be published in J. Phys.:
Condens. Matte
Glasses in hard spheres with short-range attraction
We report a detailed experimental study of the structure and dynamics of
glassy states in hard spheres with short-range attraction. The system is a
suspension of nearly-hard-sphere colloidal particles and non-adsorbing linear
polymer which induces a depletion attraction between the particles. Observation
of crystallization reveals a re-entrant glass transition. Static light
scattering shows a continuous change in the static structure factors upon
increasing attraction. Dynamic light scattering results, which cover 11 orders
of magnitude in time, are consistent with the existence of two distinct kinds
of glasses, those dominated by inter-particle repulsion and caging, and those
dominated by attraction. Samples close to the `A3 point' predicted by mode
coupling theory for such systems show very slow, logarithmic dynamics.Comment: 22 pages, 18 figure
- …