5,361 research outputs found
Pauli problem for a spin of arbitrary length: A simple method to determine its wave function
The problem of determining a pure state vector from measurements is investigated for a quantum spin of arbitrary length. Generically, only a finite number of wave functions is compatible with the intensities of the spin components in two different spatial directions, measured by a Stern-Gerlach apparatus. The remaining ambiguity can be resolved by one additional well-defined measurement. This method combines efficiency with simplicity: only a small number of quantities have to be measured and the experimental setup is elementary. Other approaches to determine state vectors from measurements, also known as the ‘‘Pauli problem,’’ are reviewed for both spin and particle systems
The Statistics of the BATSE Spectral Features
The absence of a BATSE line detection in a gamma-ray burst spectrum during
the mission's first six years has led to a statistical analysis of the
occurrence of lines in the BATSE burst database; this statistical analysis will
still be relevant if lines are detected. We review our methodology, and present
new simulations of line detectability as a function of the line parameters. We
also discuss the calculation of the number of ``trials'' in the BATSE database,
which is necessary for our line detection criteria.Comment: 5 pages, 2 figures, AIPPROC LaTeX, to appear in "Gamma-Ray Bursts,
4th Huntsville Symposium," eds. C. Meegan, R. Preece and T. Koshu
Determining a quantum state by means of a single apparatus
The unknown state \hrho of a quantum system S is determined by letting it
interact with an auxiliary system A, the initial state of which is known. A
one-to-one mapping can thus be realized between the density matrix \hrho and
the probabilities of occurrence of the eigenvalues of a single and factorized
observable of S+A, so that \hrho can be determined by repeated measurements
using a single apparatus. If S and A are spins, it suffices to measure
simultaneously their -components after a controlled interaction. The most
robust setups are determined in this case, for an initially pure or a
completely disordered state of A. They involve an Ising or anisotropic
Heisenberg coupling and an external field.Comment: 5 pages revte
Target Mass Monitoring and Instrumentation in the Daya Bay Antineutrino Detectors
The Daya Bay experiment measures sin^2 2{\theta}_13 using functionally
identical antineutrino detectors located at distances of 300 to 2000 meters
from the Daya Bay nuclear power complex. Each detector consists of three nested
fluid volumes surrounded by photomultiplier tubes. These volumes are coupled to
overflow tanks on top of the detector to allow for thermal expansion of the
liquid. Antineutrinos are detected through the inverse beta decay reaction on
the proton-rich scintillator target. A precise and continuous measurement of
the detector's central target mass is achieved by monitoring the the fluid
level in the overflow tanks with cameras and ultrasonic and capacitive sensors.
In addition, the monitoring system records detector temperature and levelness
at multiple positions. This monitoring information allows the precise
determination of the detectors' effective number of target protons during data
taking. We present the design, calibration, installation and in-situ tests of
the Daya Bay real-time antineutrino detector monitoring sensors and readout
electronics.Comment: 22 pages, 20 figures; accepted by JINST. Changes in v2: minor
revisions to incorporate editorial feedback from JINS
The BATSE Gamma-Ray Burst Spectral Catalog. I. High Time Resolution Spectroscopy of Bright Bursts using High Energy Resolution Data
This is the first in a series of gamma-ray burst spectroscopy catalogs from
the Burst And Transient Source Experiment (BATSE) on the Compton Gamma Ray
Observatory, each covering a different aspect of burst phenomenology. In this
paper, we present time-sequences of spectral fit parameters for 156 bursts
selected for either their high peak flux or fluence. All bursts have at least
eight spectra in excess of 45 sigma above background and span burst durations
from 1.66 to 278 s. Individual spectral accumulations are typically 128 ms long
at the peak of the brightest events, but can be as short as 16 ms, depending on
the type of data selected. We have used mostly high energy resolution data from
the Large Area Detectors, covering an energy range of typically 28 - 1800 keV.
The spectral model chosen is from a small empirically-determined set of
functions, such as the well-known `GRB' function, that best fits the
time-averaged burst spectra. Thus, there are generally three spectral shape
parameters available for each of the 5500 total spectra: a low-energy power-law
index, a characteristic break energy and possibly a high-energy power-law
index. We present the distributions of the observed sets of these parameters
and comment on their implications. The complete set of data that accompanies
this paper is necessarily large, and thus is archived electronically at:
http://www.journals.uchicago.edu/ApJ/journal/.Comment: Accepted for publication: ApJS, 125. 38 pages, 9 figures;
supplementary electronic archive to be published by ApJ; available from lead
author upon reques
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