25,632 research outputs found
Determination of the Gaugino Mass Parameter M_1 in Different Linear Collider Modes
We study the different linear collider modes with regard to the determination
of the gaugino mass parameter M_1. In a specific mSUGRA inspired scenario we
compare four processes with polarized beams: (a) e+ e- --> neutralino_1
neutralino_2 --> neutralino_1 neutralino_1 e+ e-, (b) e- gamma --> neutralino_1
selectron_{L/R} --> neutralino_1 neutralino_1 e-, (c) gamma gamma -->
chargino_1^+ chargino_1^- --> neutralino_1 neutralino_1 e+ e- neutrino_e
anti-neutrino_e, (d) e- e- --> selectron_{L/R} selectron_{L/R} --> neutralino_1
neutralino_1 e- e-.Comment: 5 pages, 8 figures, LaTex, Talk given at the 5th International Linear
Collider Workshop (LCWS 2000), Fermilab, Batavia, Illinois, Oct. 24-28, 200
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 1: Executive summary
The likely system concepts which might be representative of NASA and DoD space programs in the 1980-2000 time period were studied along with the programs' likely needs for major space transportation vehicles, orbital support vehicles, and technology developments which could be shared by the military and civilian space establishments in that time period. Such needs could then be used by NASA as an input in determining the nature of its long-range development plan. The approach used was to develop a list of possible space system concepts (initiatives) in parallel with a list of needs based on consideration of the likely environments and goals of the future. The two lists thus obtained represented what could be done, regardless of need; and what should be done, regardless of capability, respectively. A set of development program plans for space application concepts was then assembled, matching needs against capabilities, and the requirements of the space concepts for support vehicles, transportation, and technology were extracted. The process was pursued in parallel for likely military and civilian programs, and the common support needs thus identified
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 2: Final report
The results are presented of a study which identifies over 100 new and highly capable space systems for the 1980-2000 time period: civilian systems which could bring benefits to large numbers of average citizens in everyday life, much enhance the kinds and levels of public services, increase the economic motivation for industrial investment in space, expand scientific horizons; and, in the military area, systems which could materially alter current concepts of tactical and strategic engagements. The requirements for space transportation, orbital support, and technology for these systems are derived, and those requirements likely to be shared between NASA and the DoD in the time period identified. The high leverage technologies for the time period are identified as very large microwave antennas and optics, high energy power subsystems, high precision and high power lasers, microelectronic circuit complexes and data processors, mosaic solid state sensing devices, and long-life cryogenic refrigerators
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 3: Detailed data. Part 1: Catalog of initiatives, functional options, and future environments and goals
The following areas were discussed in relation to a study of the commonality of space vehicle applications to future national needs: (1) index of initiatives (civilian observation, communication, support), brief illustrated description of each initiative, time periods (from 1980 to 2000+) for implementation of these initiatives; (2) data bank of functional system options, presented in the form of data sheets, one for each of the major functions, with the system option for near-term, midterm, and far-term space projects applicable to each subcategory of functions to be fulfilled; (3) table relating initiatives and desired goals (public service and humanistic, materialistic, scientific and intellectual); and (4) data on size, weight and cost estimations
On the spectrum of Farey and Gauss maps
In this paper we introduce Hilbert spaces of holomorphic functions given by
generalized Borel and Laplace transforms which are left invariant by the
transfer operators of the Farey map and its induced version, the Gauss map,
respectively. By means of a suitable operator-valued power series we are able
to study simultaneously the spectrum of both these operators along with the
analytic properties of the associated dynamical zeta functions.Comment: 23 page
Polarization-selective excitation of N-V centers in diamond
The nitrogen-vacancy (N-V) center in diamond is promising as an electron spin
qubit due to its long-lived coherence and optical addressability. The ground
state is a spin triplet with two levels () degenerate at zero
magnetic field. Polarization-selective microwave excitation is an attractive
method to address the spin transitions independently, since this allows
operation down to zero magnetic field. Using a resonator designed to produce
circularly polarized microwaves, we have investigated the polarization
selection rules of the N-V center. We first apply this technique to N-V
ensembles in [100] and [111]-oriented samples. Next, we demonstrate an imaging
technique, based on optical polarization dependence, that allows rapid
identification of the orientations of many single N-V centers. Finally, we test
the microwave polarization selection rules of individual N-V centers of known
orientation
Evidence for a Galactic gamma ray halo
We present quantitative statistical evidence for a -ray emission halo
surrounding the Galaxy. Maps of the emission are derived. EGRET data were
analyzed in a wavelet-based non-parametric hypothesis testing framework, using
a model of expected diffuse (Galactic + isotropic) emission as a null
hypothesis. The results show a statistically significant large scale halo
surrounding the center of the Milky Way as seen from Earth. The halo flux at
high latitudes is somewhat smaller than the isotropic gamma-ray flux at the
same energy, though of the same order (O(10^(-7)--10^(-6)) ph/cm^2/s/sr above 1
GeV).Comment: Final version accepted for publication in New Astronomy. Some
additional results/discussion included, along with entirely revised figures.
19 pages, 15 figures, AASTeX. Better quality figs (PS and JPEG) are available
at http://tigre.ucr.edu/halo/paper.htm
Microfield distributions in strongly coupled two-component plasmas
The electric microfield distribution at charged particles is studied for
two-component electron-ion plasmas using molecular dynamics simulation and
theoretical models. The particles are treated within classical statistical
mechanics using an electron-ion Coulomb potential regularized at distances less
than the de Broglie length to take into account the quantum-diffraction
effects. The potential-of-mean-force (PMF) approximation is deduced from a
canonical ensemble formulation. The resulting probability density of the
electric microfield satisfies exactly the second-moment sum rule without the
use of adjustable parameters. The correlation functions between the charged
radiator and the plasma ions and electrons are calculated using molecular
dynamics simulations and the hypernetted-chain approximation for a
two-component plasma. It is shown that the agreement between the theoretical
models for the microfield distributions and the simulations is quite good in
general.Comment: 18 figures. Submitted to Phys. Rev.
The final COS-B database: In-flight calibration of instrumental parameters
A method for the determination of temporal variation of sensitivity is designed to find a set of parameters which lead to maximum consistency between the intensities derived from different observation periods. This method is briefly described and the resulting sensitivity and background variations presented
Investigation of the stability of commercial neutron probes
At the Paul Scherrer Institute's Calibration Laboratory, neutron reference fields are provided for the calibration of ambient and personal dose equivalent (rate) metres and passive dosemeters. To ensure traceability to the standards of the Physikalisch-Technische Bundesanstalt (PTB) in Germany, the neutron fields are characterised by means of a PTB-calibrated Berthold LB6411 neutron probe which is used as a secondary standard. The LB6411 detector suffers from an unstable, increasing dose rate reading in the order of up to +5 % (according to the manufacturers, this is due to a charging effect in the 3He proportional counter). In a calibration, this instability is usually corrected for based on the reading obtained with a test source. In this work, the instability was investigated by means of measurements under irradiation with ambient dose equivalent rates up to 24 mSv h-1 for up to 20 h and compared with the behaviour of an LB6419 and a Thermo Wendi-2 probe. The reading of the instruments was found to reach a plateau, e.g. it becomes stable after ∼90 min during irradiation with 10 mSv h-1 neutrons. The plateau is reached faster for higher dose rates. This supports the interpretation as a charging effect in the proportional counter. The effect could also be duplicated in an irradiation with photons from a 137Cs source. The decay time of the accumulated charge was found to be very long, i.e. the instrument showed a stable reproducible reading for up to 6 h after the plateau was reached. From these observations, a conditioning procedure was derived which ensures a stable operation of the instrument after an irradiation of the instrument preceding its use in the reference measurement
- …