267 research outputs found
A Natural Framework for Solar and 17 keV Neutrinos
Motivated by recent experimental claims for the existence of a 17 keV
neutrino and by the solar neutrino problem, we construct a class of models
which contain in their low-energy spectrum a single light sterile neutrino and
one or more Nambu-Goldstone bosons. In these models the required pattern of
breaking of lepton-number symmetry takes place near the electroweak scale and
all mass heirarchies are technically natural. The models are compatible with
all cosmological and astrophysical constraints, and can solve the solar
neutrino problem via either the MSW effect or vacuum oscillations. The deficit
in atmospheric muon neutrinos seen in the Kamiokande and IMB detectors can also
be explained in these models.Comment: 23 page
Constraints on radiative decay of the 17-keV neutrino from COBE Measurements
It is shown that, for a nontrivial radiative decay channel of the 17-keV
neutrino, the photons would distort the microwave background radiation through
ionization of the universe. The constraint on the branching ratio of such
decays from COBE measurements is found to be more stringent than that from
other considerations. The limit on the branching ratio in terms of the Compton
parameter is for an
universe.Comment: 7 pages. (figures will be sent on request) (To appear in Phys. Rev.
D.
Fluorescence Efficiency and Visible Re-emission Spectrum of Tetraphenyl Butadiene Films at Extreme Ultraviolet Wavelengths
A large number of current and future experiments in neutrino and dark matter
detection use the scintillation light from noble elements as a mechanism for
measuring energy deposition. The scintillation light from these elements is
produced in the extreme ultraviolet (EUV) range, from 60 - 200 nm. Currently,
the most practical technique for observing light at these wavelengths is to
surround the scintillation volume with a thin film of Tetraphenyl Butadiene
(TPB) to act as a fluor. The TPB film absorbs EUV photons and reemits visible
photons, detectable with a variety of commercial photosensors. Here we present
a measurement of the re-emission spectrum of TPB films when illuminated with
128, 160, 175, and 250 nm light. We also measure the fluorescence efficiency as
a function of incident wavelength from 120 to 250 nm.Comment: 15 pages, 9 figures, Submitted to Nuclear Instruments and Methods in
Physics Research Section A: Accelerators, Spectrometers, Detectors and
Associated Equipmen
Muon-Induced Background Study for Underground Laboratories
We provide a comprehensive study of the cosmic-ray muon flux and induced
activity as a function of overburden along with a convenient parameterization
of the salient fluxes and differential distributions for a suite of underground
laboratories ranging in depth from 1 to 8 km.w.e.. Particular attention
is given to the muon-induced fast neutron activity for the underground sites
and we develop a Depth-Sensitivity-Relation to characterize the effect of such
background in experiments searching for WIMP dark matter and neutrinoless
double beta decay.Comment: 18 pages, 28 figure
Systematic Study of Fermion Masses and Mixing Angles in Horizontal SU(2) Gauge Theory
Despite its great success in explaining the basic interactions of nature, the
standard model suffers from an inability to explain the observed masses of the
fundamental particles and the weak mixing angles between them. We shall survey
a set of possible extensions to the standard model, employing an SU(2)
``horizontal'' gauge symmetry between the particle generations, to see what
light they can shed on this problem.Comment: 43 pages, 4 figures (available by postal mail on request), OZ-92/0
A proposed measurement of the ß asymmetry in neutron decay with the Los Alamos Ultra-Cold Neutron Source
This article reviews the status of an experiment to study the neutron spin-electron angular correlation with the Los Alamos Ultra-Cold Neutron (UCN) source. The experiment will generate UCNs from a novel solid deuterium, spallation source, and polarize them in a solenoid magnetic field. The experiment spectrometer will consist of a neutron decay region in a solenoid magnetic field combined with several different detector possibilities. An electron beam and a magnetic spectrometer will provide a precise, absolute calibration for these detectors. An A-correlation measurement with a relative precision of 0.2% is expected by the end of 2002
Scintillation time dependence and pulse shape discrimination in liquid argon
Using a single-phase liquid argon detector with a signal yield of 4.85
photoelectrons per keV of electronic-equivalent recoil energy (keVee), we
measure the scintillation time dependence of both electronic and nuclear
recoils in liquid argon down to 5 keVee. We develop two methods of pulse shape
discrimination to distinguish between electronic and nuclear recoils. Using one
of these methods, we measure a background and statistics-limited level of
electronic recoil contamination to be between 60 and 128 keV
of nuclear recoil energy (keVr) for a nuclear recoil acceptance of 50% with no
nuclear recoil-like events above 72 keVr. Finally, we develop a maximum
likelihood method of pulse shape discrimination using the measured
scintillation time dependence and predict the sensitivity to WIMP-nucleon
scattering in three configurations of a liquid argon dark matter detector.Comment: 13 pages, 14 figures, Revision 3 (published
Coupling Superconducting Qubits via a Cavity Bus
Superconducting circuits are promising candidates for constructing quantum
bits (qubits) in a quantum computer; single-qubit operations are now routine,
and several examples of two qubit interactions and gates having been
demonstrated. These experiments show that two nearby qubits can be readily
coupled with local interactions. Performing gates between an arbitrary pair of
distant qubits is highly desirable for any quantum computer architecture, but
has not yet been demonstrated. An efficient way to achieve this goal is to
couple the qubits to a quantum bus, which distributes quantum information among
the qubits. Here we show the implementation of such a quantum bus, using
microwave photons confined in a transmission line cavity, to couple two
superconducting qubits on opposite sides of a chip. The interaction is mediated
by the exchange of virtual rather than real photons, avoiding cavity induced
loss. Using fast control of the qubits to switch the coupling effectively on
and off, we demonstrate coherent transfer of quantum states between the qubits.
The cavity is also used to perform multiplexed control and measurement of the
qubit states. This approach can be expanded to more than two qubits, and is an
attractive architecture for quantum information processing on a chip.Comment: 6 pages, 4 figures, to be published in Natur
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