27,027 research outputs found
Neutrino Mass and Oscillations
Current evidence for neutrino oscillation is reviewed, some areas for closer
investigation are suggested, and a plausible future experimental program is
summarized.Comment: Text of talk presented at Lepton-Photon 99 Conference, Stanford, Aug.
9-14, 1999; to be published in the Proceedings. LaTeX, 22 pages, 4 figures, 6
Postscript file
Direct Measurement of Neutrino Mass
The sum of the masses of the three neutrino mass eigenstates is now
constrained both from above and below, and lies between 55 and 6900 meV. The
lower limit is set by neutrino oscillations and the fact that masses are
non-negative. The upper limit is set by laboratory measurements on the beta
decay of tritium. These determinations share a common characteristic of being
essentially model independent, or "direct." The clustering on large scales in
the universe depends on this quantity, and, within the framework of Lambda-CDM
cosmology, favors a mass sum below about 600 meV. In this article, the
laboratory approach to neutrino mass via beta decay is emphasized, particularly
an experiment now under construction, KATRIN, on the beta decay of tritium.
Another candidate beta-active nuclide, Re-187, offers an advantage in phase
space but calls for a very different experimental approach.Comment: 6 pages, 2 figures, for Proceedings of Carolina International
Symposium on Neutrino Physics, Columbia, SC, May 15-17, 2008. To be published
in J.Phys.: Conf. Serie
Extremal extensions of entanglement witnesses: Unearthing new bound entangled states
In this paper, we discuss extremal extensions of entanglement witnesses based
on Choi's map. The constructions are based on a generalization of the Choi map
due to Osaka, from which we construct entanglement witnesses. These extremal
extensions are powerful in terms of their capacity to detect entanglement of
positive under partial transpose (PPT) entangled states and lead to unearthing
of entanglement of new PPT states. We also use the Cholesky-like decomposition
to construct entangled states which are revealed by these extremal entanglement
witnesses.Comment: 8 pages 6 figures revtex4-
Transport theory yields renormalization group equations
We show that dissipative transport and renormalization can be described in a
single theoretical framework. The appropriate mathematical tool is the
Nakajima-Zwanzig projection technique. We illustrate our result in the case of
interacting quantum gases, where we use the Nakajima-Zwanzig approach to
investigate the renormalization group flow of the effective two-body
interaction.Comment: 11 pages REVTeX, twocolumn, no figures; revised version with
additional examples, to appear in Phys. Rev.
Search for the second forbidden beta decay of 8B to the ground state of 8Be
A significant decay branch of 8B to the ground state of 8Be would extend the
solar neutrino spectrum to higher energies than anticipated in the standard
solar models. These high-energy neutrinos would affect current neutrino
oscillation results and also would be a background to measurements of the hep
process. We have measured the delayed alpha particles from the decay of 8B,
with the goal of observing the two 46-keV alpha particles arising from the
ground-state decay. The 8B was produced using an in-flight radioactive beam
technique. It was implanted in a silicon PIN-diode detector that was capable of
identifying the alpha-particles from the 8Be ground state. From this
measurement we find an upper limit (at 90% confidence level) of 7.3 x 10^{-5}
for the branching ratio to the ground state. In addition to describing this
measurement, we present a theoretical calculation for this branching ratio.Comment: One reference corrected. Minor edits in tex
KATRIN: an experiment to measure the neutrino mass
KATRIN is a very large scale tritium-beta-decay experiment to determine the
mass of the neutrino. It is presently under construction at the
Forschungszentrum Karlsruhe, and makes use of the Tritium Laboratory built
there for the ITER project. The combination of a very large retarding-potential
electrostatic-magnetic spectrometer and an intense gaseous molecular tritium
source makes possible a sensitivity to neutrino mass of 0.2 eV, about an order
of magnitude below present laboratory limits. The measurement is kinematic and
independent of whether the neutrino is Dirac or Majorana. The status of the
project is summarized briefly in this report.Comment: 3 pages, 1 figure. For Proceedings of Topics in Astroparticle and
Underground Physics, Sendai, Sept. 2007. To be published in J.Phys.: Conf.
Serie
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