393 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
Treatment of the background error in the statistical analysis of Poisson processes
The formalism that allows to take into account the error sigma_b of the
expected mean background b in the statistical analysis of a Poisson process
with the frequentistic method is presented. It is shown that the error sigma_b
cannot be neglected if it is not much smaller than sqrt(b). The resulting
confidence belt is larger that the one for sigma_b=0, leading to larger
confidence intervals for the mean mu of signal events.Comment: 15 pages including 2 figures, RevTeX. Final version published in
Phys. Rev. D 59 (1999) 11300
The Architecture of MEG Simulation and Analysis Software
MEG (Mu to Electron Gamma) is an experiment dedicated to search for the
decay that is strongly suppressed in the Standard
Model but predicted in several Super Symmetric extensions of it at an
accessible rate. MEG is a small-size experiment ( physicists at
any time) with a life span of about 10 years. The limited human resource
available, in particular in the core offline group, emphasized the importance
of reusing software and exploiting existing expertise. Great care has been
devoted to provide a simple system that hides implementation details to the
average programmer. That allowed many members of the collaboration to
contribute to the development of the software of the experiment with limited
programming skill. The offline software is based on two frameworks: {\bf REM}
in FORTRAN 77 used for the event generation and detector simulation package
{\bf GEM}, based on GEANT 3, and {\bf ROME} in C++ used in the readout
simulation {\bf Bartender} and in the reconstruction and analysis program {\bf
Analyzer}. Event display in the simulation is based on GEANT 3 graphic
libraries and in the reconstruction on ROOT graphic libraries. Data are stored
in different formats in various stage of the processing. The frameworks include
utilities for input/output, database handling and format conversion transparent
to the user.Comment: Presented at the IEEE NSS Knoxville, 2010 Revised according to
referee's remarks Accepted by European Physical Journal Plu
Improved Probability Method for Estimating Signal in the Presence of Background
A suggestion is made for improving the Feldman Cousins method of estimating
signal counts in the presence of background. The method concentrates on finding
essential information about the signal and ignoring extraneous information
about background. An appropriate method is found which uses the condition that
the number of background events obtained does not exceed the total number of
events obtained. Several alternative approaches are explored.Comment: Modified 12/21 for singlespace to save trees, 9 pages, 1 figure.
Modified 8/11/99 to add small modifications made for the Phys. Rev. articl
Search for Solar Axions Produced in the Reaction
A search for the axioelectric absorption of 5.5-MeV solar axions produced in
the reaction was performed with
two BGO detectors placed inside a low-background setup. A model independent
limit on axion-photon and axion-nucleon couplings was obtained: . Constraints on the axion-electron
coupling constant were obtained for axions with masses in the MeV
range: . The solar positron flux from
decay was determined for axions with masses . Using the existing experimental data on the interplanetary positron
flux, a new constraint on the axion-electron coupling constant for axions with
masses in the MeV range was obtained: .Comment: 6 pages, 5 figure
Search for a Lorentz invariance violation in atmospheric neutrino oscillations using MACRO data
The energy spectrum of neutrino-induced upward-going muons in MACRO was
analysed in terms of special relativity principles violating effects, keeping
standard mass-induced atmospheric neutrino oscillations as the dominant source
of nu_mu nu_tau transitions. The data disfavour these exotic possibilities
even at a sub-dominant level, and stringent 90% C.L. limits are placed on the
Lorentz invariance violation parameters. These limits can also be
re-interpreted as upper bounds on the parameters describing violation of the
Equivalence Principle.Comment: 8 pages, 5 EPS figures, uses article.sty. Invited talk at C2CR 2005,
From Colliders to Cosmic Rays, Prague, Czech Republic, 7-13 September 200
Are there nu_mu or nu_tau in the flux of solar neutrinos on earth?
Using the model independent method of Villante, Fiorentini, Lisi, Fogli,
Palazzo, and the rates measured in the SNO and Super-Kamiokande solar neutrino
experiment, we calculate the amount of active nu_mu or nu_tau present in the
flux of solar neutrinos on Earth. We show that the probability of
nu_e->nu_{mu,tau} transitions is larger than zero at 99.89% CL. We find that
the averaged flux of nu_{mu,tau} on Earth is larger than 0.17 times the 8B nu_e
flux predicted by the BP2000 Standard Solar Model at 99% CL. We discuss also
the consequences of possible nu_e->anti-nu_{mu,tau} or nu_e->anti-nu_e
transitions of solar neutrinos. We derive a model-independent lower limit of
0.52 at 99% CL for the ratio of the 8B nu_e flux produced in the Sun and its
value in the BP2000 Standard Solar Model.Comment: 5 pages. Added discussion on possible nu_e->anti-nu_{mu,tau} or
nu_e->anti-nu_e transition
Detection potential to point-like neutrino sources with the NEMO-km3 telescope
The NEMO Collaboration is conducting an R&D activity towards the construction
of a Mediterranean km3 neutrino telescope. In this work, we present the results
of Monte Carlo simulation studies on the capability of the proposed NEMO
telescope to detect and identify point-like sources of high energy muon
neutrinos.Comment: To be published on BCN06 proceedings (Barcelona, July 4-7, 2006
Identification of high energy gamma-ray sources and source populations in the era of deep all-sky coverage
A large fraction of the anticipated source detections by the Gamma-ray Large
Area Space Telescope (GLAST-LAT) will initially be unidentified. We argue that
traditional approaches to identify individuals and/or populations of gamma ray
sources will encounter procedural limitations. Those limitations are discussed
on the background of source identifications from EGRET observations. Generally,
our ability to classify (faint) source populations in the anticipated GLAST
dataset with the required degree of statistical confidence will be hampered by
sheer source wealth. A new paradigm for achieving the classification of gamma
ray source populations is discussed.Comment: Comments: 6 pages, 2 figures, Accepted for publication in
Astrophysics and Space Science, Proc. of "The Multi-Messenger Approach to
High-Energy Gamma-ray Sources (Third Workshop on the Nature of Unidentified
High-Energy Sources)", Barcelona, July 4-7, 200
Optimal generalization of power filters for gravitational wave bursts, from single to multiple detectors
Searches for gravitational wave signals which do not have a precise model
describing the shape of their waveforms are often performed using power
detectors based on a quadratic form of the data. A new, optimal method of
generalizing these power detectors so that they operate coherently over a
network of interferometers is presented. Such a mode of operation is useful in
obtaining better detection efficiencies, and better estimates of the position
of the source of the gravitational wave signal. Numerical simulations based on
a realistic, computationally efficient hierarchical implementation of the
method are used to characterize its efficiency, for detection and for position
estimation. The method is shown to be more efficient at detecting signals than
an incoherent approach based on coincidences between lists of events. It is
also shown to be capable of locating the position of the source.Comment: 16 pages, 5 figure
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