12,977 research outputs found
Comment on "Including Systematic Uncertainties in Confidence Interval Construction for Poisson Statistics"
The incorporation of systematic uncertainties into confidence interval
calculations has been addressed recently in a paper by Conrad et al. (Physical
Review D 67 (2003) 012002). In their work, systematic uncertainities in
detector efficiencies and background flux predictions were incorporated
following the hybrid frequentist-Bayesian prescription of Cousins and Highland,
but using the likelihood ratio ordering of Feldman and Cousins in order to
produce "unified" confidence intervals. In general, the resulting intervals
behaved as one would intuitively expect, i.e. increased with increasing
uncertainties. However, it was noted that for numbers of observed events less
than or of order of the expected background, the intervals could sometimes
behave in a completely counter-intuitive fashion -- being seen to initially
decrease in the face of increasing uncertainties, but only for the case of
increasing signal efficiency uncertainty. In this comment, we show that the
problematic behaviour is due to integration over the signal efficiency
uncertainty while maximising the best fit alternative hypothesis likelihood. If
the alternative hypothesis likelihood is determined by unconditionally
maximising with respect to both the unknown signal and signal efficiency
uncertainty, the limits display the correct intuitive behaviour.Comment: Submitted to Physical Review
Technology requirements for future Earth-to-geosynchronous orbit transportation systems. Volume 1: Executive summary
Technologies including accelerated technology that are critical to performance and/or provide cost advantages for future space transportation systems are identified. Mission models are scoped and include priority missions, and cargo missions. Summary data, providing primary design concepts and features, are given for the SSTO, HLLV, POTV, and LCOTV vehicles. Significant system costs and total system costs in terms of life cycle costs in both discounted and undiscounted dollars are summarized for each of the vehicles
Sterile Neutrino Fits to Short Baseline Neutrino Oscillation Measurements
This paper reviews short baseline oscillation experiments as interpreted
within the context of one, two, and three sterile neutrino models associated
with additional neutrino mass states in the ~1 eV range. Appearance and
disappearance signals and limits are considered. We show that fitting short
baseline data sets to a (3+3) model, defined by three active and three sterile
neutrinos, results in an overall goodness of fit of 67%, and a compatibility of
90% among all data sets -- to be compared to the compatibility of 0.043% and
13% for a (3+1) and a (3+2) model, respectively. While the (3+3) fit yields the
highest quality overall, it still finds inconsistencies with the MiniBooNE
appearance data sets; in particular, the global fit fails to account for the
observed MiniBooNE low-energy excess. Given the overall improvement, we
recommend using the results of (3+2) and (3+3) fits, rather than (3+1) fits,
for future neutrino oscillation phenomenology. These results motivate the
pursuit of further short baseline experiments, such as those reviewed in this
paper.Comment: Submitted to Advances in High Energy Physics Special Issue on
Neutrino Physic
Technology requirements for future Earth-to-geosynchronous orbit transportation systems. Volume 3: Appendices
Technological requirements and forecasts of rocket engine parameters and launch vehicles for future Earth to geosynchronous orbit transportation systems are presented. The parametric performance, weight, and envelope data for the LOX/CH4, fuel cooled, staged combustion cycle and the hydrogen cooled, expander bleed cycle engine concepts are discussed. The costing methodology and ground rules used to develop the engine study are summarized. The weight estimating methodology for winged launched vehicles is described and summary data, used to evaluate and compare weight data for dedicated and integrated O2/H2 subsystems for the SSTO, HLLV and POTV are presented. Detail weights, comparisons, and weight scaling equations are provided
The Desktop Muon Detector: A simple, physics-motivated machine- and electronics-shop project for university students
This paper describes an undergraduate-level physics project that incorporates
various aspects of machine- and electronics-shop technical development. The
desktop muon detector is a self-contained apparatus that employs plastic
scintillator as a detection medium and a silicon photomultiplier for light
collection. These detectors can be used in conjunction with the provided
software to make interesting physics measurements. The total cost of each
counter is approximately $100.Comment: 29 pages, 14 figure
A Measurement of the Absorption of Liquid Argon Scintillation Light by Dissolved Nitrogen at the Part-Per-Million Level
We report on a measurement of the absorption length of scintillation light in
liquid argon due to dissolved nitrogen at the part-per-million (ppm) level. We
inject controlled quantities of nitrogen into a high purity volume of liquid
argon and monitor the light yield from an alpha source. The source is placed at
different distances from a cryogenic photomultiplier tube assembly. By
comparing the light yield from each position we extract the absorption cross
section of nitrogen. We find that nitrogen absorbs argon scintillation light
with strength of ,
corresponding to an absorption cross section of . We obtain the relationship
between absorption length and nitrogen concentration over the 0 to 50 ppm range
and discuss the implications for the design and data analysis of future large
liquid argon time projection chamber (LArTPC) detectors. Our results indicate
that for a current-generation LArTPC, where a concentration of 2 parts per
million of nitrogen is expected, the attenuation length due to nitrogen will be
meters.Comment: v2: Correct mistake in molecular absorption cross section
calculation, and a minor typo in fig
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