47 research outputs found
A Possible Solution to the Tritium Endpoint Problem
Scalar or right-chiral interaction currents may be expected to produce a
neutrino coupled to the electron which is different from, and perhaps even
orthogonal to, that coupled to the electron by the standard model weak
interaction. We show that, using reasonable parameter values for such
additional interactions, it is possible to generate a spectrum which, if
analyzed in the manner commonly employed by experimental groups, produces a
negative neutrino mass-squared.Comment: LaTeX, 7 pages, 1 Postscript figure, submitted to Phys. Lett.
Tritium Beta Decay, Neutrino Mass Matrices and Interactions Beyond the Standard Model
The interference of charge-changing interactions, weaker than the V-A
Standard Model (SM) interaction and having a different Lorentz structure, with
that SM interaction, can, in principle, produce effects near the end point of
the Tritium beta decay spectrum which are of a different character from those
produced by the purely kinematic effect of neutrino mass expected in the
simplest extension of the SM. We show that the existence of more than one mass
eigenstate can lead to interference effects at the end point that are stronger
than those occurring over the entire spectrum. We discuss these effects both
for the special case of Dirac neutrinos and the more general case of Majorana
neutrinos and show that, for the present precision of the experiments, one
formula should suffice to express the interference effects in all cases.
Implications for "sterile" neutrinos are noted.Comment: 32 pages, LaTeX, 6 figures, PostScript; full discussion and changes
in notation from Phys. Lett. B440 (1998) 89, nucl-th/9807057; submitted to
Phys. Rev.
Neutrino Clustering in the Galaxy with a Global Monopole
In spherically symmetric, static spacetime, we show that only j=1/2 fermions
can satisfy both Einstein's field equation and Dirac's equation. It is also
shown that neutrinos are able to have effective masses and cluster in the
galactic halo when they are coupled to a global monopole situated at the
galactic core. Astronomical implications of the results are discussed.Comment: 8 pages, Revtex
Non-standard Hamiltonian effects on neutrino oscillations
We investigate non-standard Hamiltonian effects on neutrino oscillations,
which are effective additional contributions to the vacuum or matter
Hamiltonian. Since these effects can enter in either flavor or mass basis, we
develop an understanding of the difference between these bases representing the
underlying theoretical model. In particular, the simplest of these effects are
classified as ``pure'' flavor or mass effects, where the appearance of such a
``pure'' effect can be quite plausible as a leading non-standard contribution
from theoretical models. Compared to earlier studies investigating particular
effects, we aim for a top-down classification of a possible ``new physics''
signature at future long-baseline neutrino oscillation precision experiments.
We develop a general framework for such effects with two neutrino flavors and
discuss the extension to three neutrino flavors, as well as we demonstrate the
challenges for a neutrino factory to distinguish the theoretical origin of
these effects with a numerical example. We find how the precision measurement
of neutrino oscillation parameters can be altered by non-standard effects alone
(not including non-standard interactions in the creation and detection
processes) and that the non-standard effects on Hamiltonian level can be
distinguished from other non-standard effects (such as neutrino decoherence and
decay) if we consider specific imprint of the effects on the energy spectra of
several different oscillation channels at a neutrino factory.Comment: 30 pages, 6 figures, LaTeX, final version, published in Eur.Phys.J.
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Mid-rapidity anti-proton to proton ratio from Au+Au collisions at GeV
We report results on the ratio of mid-rapidity anti-proton to proton yields
in Au+Au collisions at \rts = 130 GeV per nucleon pair as measured by the
STAR experiment at RHIC. Within the rapidity and transverse momentum range of
and 0.4 1.0 GeV/, the ratio is essentially independent of
either transverse momentum or rapidity, with an average of for minimum bias collisions. Within errors, no
strong centrality dependence is observed. The results indicate that at this
RHIC energy, although the -\pb pair production becomes important at
mid-rapidity, a significant excess of baryons over anti-baryons is still
present.Comment: 5 pages, 3 figures, accepted by Phys. Rev. Let
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High-intensity neutrino facility at LAMPF
A high-intensity neutrino facility is being proposed to be built at LAMPF. This facility, which uses 100 ..mu..A of protons at 800 MeV incident upon a graphite target, will be run in two modes. The first mode will use the usual 750-..mu..s pulse width at 12 Hertz at LAMPF. The second one will use the Proton Storage Ring (PSR), currently under construction, and compress the proton bursts to 0.270 ..mu..s. In this mode, pure beams of high-intensity neutrinos and antineutrinos will be created. Using this facility, oen can achieve very sensitive limits on neutrino-electron scattering. In addition, there are many other interesting neutrino scattering reactions to study
Type C oncornavirus isolation studies in systemic lupus erythematosus: I. Attempted detection by isopycnic sedimentation of 3H-uridine-labelled virions
Atom Probe Tomography at The University of Sydney
Summary: The Australian Microscopy & Microanalysis Research Facility (AMMRF) operates a national atom probe laboratory at The University of Sydney. This paperprovides a brief review and update of the technique of atom probe tomography (APT),together with a summary of recent research applications at Sydney in the scienceand technology of materials. We describe recent instrumentation advances such asthe use of laser pulsing to effect time-controlled field evaporation, the introductionof wide field of view detectors, where the solid angle for observation is increased byup to a factor of ∼20 as well as innovations in specimen preparation. We concludethat these developments have opened APT to a range of new materials that werepreviously either difficult or impossible to study using this technique because of theirpoor conductivity or brittleness