148,240 research outputs found
IceCube Sterile Neutrino Searches
Anomalies in short baseline experiments have been interpreted as evidence for
additional neutrino mass states with large mass splittings from the known,
active flavors. This explanation mandates a corresponding signature in the muon
neutrino disappearance channel, which has yet to be observed. Searches for muon
neutrino disappearance at the IceCube neutrino telescope presently provide the
strongest limits in the space of mixing angles for eV-scale sterile neutrinos.
This proceeding for the Very Large Volume Neutrino Telescopes (VLVnT) Workshop
summarizes the IceCube analyses that have searched for sterile neutrinos and
describes ongoing work toward enhanced, high-statistics sterile neutrino
searches.Comment: Proceeding for the VLVNT2018 Conferenc
Dynamical Pion Collapse and the Coherence of Conventional Neutrino Beams
In this paper we consider the coherence properties of neutrinos produced by
the decays of pions in conventional neutrino beams. Using a multi-particle
density matrix formalism we derive the oscillation probability for neutrinos
emitted by a decaying pion in an arbitrary quantum state. Then, using methods
from decoherence theory we calculate the pion state which evolves through
interaction with decay-pipe gases in a typical accelerator neutrino experiment.
These two ingredients are used to obtain the distance scales for neutrino beam
coherence loss. We find that for the known neutrino mass splittings, no
non-standard oscillation effects are expected on terrestrial baselines. Heavy
sterile neutrinos may experience terrestrial loss of coherence, and we
calculate both the distance over which this occurs and the energy resolution
required to observe the effect. By treating the pion-muon-neutrino-environment
system quantum mechanically, neutrino beam coherence properties are obtained
without assuming arbitrary spatial or temporal scales at the neutrino
production vertex.Comment: 13 pages, 10 figures. v2: Minor typographical corrections v3:
Accepted for publication in Phys.Rev.
Implementing quantum logic gates with GRAPE: principles and practicalities
We briefly describe the use of GRAPE pulses to implement quantum logic gates
in NMR quantum computers, and discuss a range of simple extensions to the core
technique. We then consider a range of difficulties which can arise in
practical implementations of GRAPE sequences, reflecting non-idealities in the
experimental systems used.Comment: 15 pages rspublic including 4 figures. This is the original
manuscript preprint form which differs slightly from the final accepted
version (Phil Trans Roy Soc A in press
The Fornax Spectroscopic Survey --- Low Surface Brightness Galaxies in Fornax
The Fornax Spectroscopic Survey is a large optical spectroscopic survey of
ALL 14,000 objects with 16.5<Bj<19.7 in a 12 sq.deg area of sky centered on the
Fornax Cluster. We are using the 400-fibre Two Degree Field spectrograph on the
Anglo-Australian Telescope: the multiplex advantage of this system allows us to
observe objects conventionally classified as `stars' as well as `galaxies'.
This is the only way to minimise selection effects caused by image
classification or assessing cluster membership.
In this paper we present the first measurements of low surface brightness
(LSB) galaxies we have detected both in the Fornax Cluster and among the
background field galaxies. The new cluster members include some very low
luminosity (M_B approx -11.5 mag) dwarf ellipticals, whereas the background LSB
galaxies are luminous (-19.6<M_B<-17.0 mag) disk-like galaxies.Comment: To appear in "The Low Surface Brightness Universe", IAU Coll 171,
eds. J.I. Davies et al., A.S.P. Conference Series. 8 pages, LaTex, 6
encapsulated ps-figures, requires paspconf.st
The design and development of a solar tracking unit
The solar tracking unit was developed to support the Laser Heterodyne Spectrometer (LHS) airborne instrument, but has application to a general class of airborne solar occultation research instruments. The unit consists of a mirror mounted on two gimbals, one of which is hollow. The mirror reflects a 7.6 cm (3.0 in.) diameter beam of sunlight through the hollow gimbal into the research instrument optical axis. A portion of the reflected sunlight is directed into a tracking telescope which uses a four quadrant silicon detector to produce the servo error signals. The colinearity of the tracker output beam and the research instrument optical axis is maintained to better than + or - 1 arc-minute. The unit is microcomputer controlled and is capable of stand alone operation, including automatic Sun acquisition or operation under the control of the research instrument
Charge control experiments on a CH-53E helicopter in a dusty environment
Charge control tests were carried out on a ground based, Marine Corps helicopter to determine if control of the electric fields acting on the engine exhaust gases could be used to reduce the electrification of the helicopter when it operated in a dusty atmosphere. The test aircraft was flown to a dusty, unpaved area and was then isolated electrically from the earth. When the helicopter engines were operated at ground idle with the rotor locked, the isolated aircraft charged positively, as had been observed previously. However, when the rotor brake was released and the turning rotor created a downdraft that raised dust clouds, the aircraft always became charged more positively, to potentials ranging form +30 to +45 kV. The dust clouds raised by the rotor downwash invariably carried negative space charges with concentrations of up to -100 nC/cu m and caused surface electric fields with strengths of up to 10 kV/m immediately down wind of the aircraft. The natural charging of the helicopter operating in these dust clouds was successfully opposed by control of the electric fields acting on the hot, electrically conductive exhaust gases. The control was achieved by placing electrostatic shield around the exhausts
Gallium Arsenide preparation and QE Lifetime Studies using the ALICE Photocathode Preparation Facility
In recent years, Gallium Arsenide (GaAs) type photocathodes have become
widely used as electron sources in modern Energy Recovery Linac based light
sources such as the Accelerators and Lasers in Combined Experiments (ALICE) at
Daresbury Laboratory and as polarised electron source for the proposed
International Linear Collider (ILC). Once activated to a Low Electron Affinity
(LEA) state and illuminated by a laser, these materials can be used as a
high-brightness source of both polarised and un-polarised electrons. This paper
presents an effective multi-stage preparation procedure including heat
cleaning, atomic hydrogen cleaning and the activation process for a GaAs
photocathode. The stability of quantum efficiency (QE) and lifetime of
activated to LEA state GaAs photocathode have been studied in the ALICE
load-lock photocathode preparation facility which has a base pressure in the
order of 10^-11 mbar. These studies are supported by further experimental
evidence from surface science techniques such as X-ray Photoelectron
Spectroscopy (XPS) to demonstrate the processes at the atomic level.Comment: Presented at First International Particle Accelerator Conference,
IPAC'10, Kyoto, Japan, from 23 to 28 May 201
- …