2,090 research outputs found
Confronting classical and Bayesian confidence limits to examples
Classical confidence limits are compared to Bayesian error bounds by studying
relevant examples. The performance of the two methods is investigated relative
to the properties coherence, precision, bias, universality, simplicity. A
proposal to define error limits in various cases is derived from the
comparison. It is based on the likelihood function only and follows in most
cases the general practice in high energy physics. Classical methods are
discarded because they violate the likelihood principle, they can produce
physically inconsistent results, suffer from a lack of precision and
generality. Also the extreme Bayesian approach with arbitrary choice of the
prior probability density or priors deduced from scaling laws is rejected.Comment: 16 pages, 12 figure
Statistics of weighted Poisson events and its applications
The statistics of the sum of random weights where the number of weights is
Poisson distributed has important applications in nuclear physics, particle
physics and astrophysics. Events are frequently weighted according to their
acceptance or relevance to a certain type of reaction. The sum is described by
the compound Poisson distribution (CPD) which is shortly reviewed. It is shown
that the CPD can be approximated by a scaled Poisson distribution (SPD). The
SPD is applied to parameter estimation in situations where the data are
distorted by resolution effects. It performs considerably better than the
normal approximation that is usually used. A special Poisson bootstrap
technique is presented which permits to derive confidence limits for
observations following the CPD.Comment: 14 pages, 2 figure
An optical readout for a fibre tracker
The performance of 16 and 64 channel photomultipliers coupled to
scintillating fibres has been tested. The devices are sensitive to single
photoelectrons, show little gain losses for magnetic fields up to 100 Gauss and
have moderate optical cross-talk. The maximum channel to channel gain
variations reach a factor two for the 16 channel version and a factor of four
for the 64 channel PM. The measurements and simulations indicate that the
photomultipliers are well suited for the light detection in fibre trackers.Comment: 11 pages, 9 picture
Holographic optical elements: Fabrication and testing
The basic properties and use of holographic optical elements were investigated to design and construct wide-angle, Fourier-transform holographic optical systems for use in a Bragg-effect optical memory. The performance characteristics are described along with the construction of the holographic system
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