122778557
Statistical methods for signal estimation of point sources of cosmic rays
The estimation of the significance of the peaks in one- and two-dimensional distributions is one of the most important problems in high-energy physics and astrophysics. The physical inference from low-statistics experiments usually is biased and many discoveries lack further confirmation. One of the typical mistakes in physical inference is the use of non-adequate statistical models. We analyze the significance of the experimental evidence in the on-going efforts of detecting the point source of cosmic rays. We found that simple statistical models (Gaussian or Poisson) did not adequately describe the experimental situation of point source searches. To avoid drawbacks related to usage of the incorrect statistical model, we introduce new extremum statistical models appropriate for the point source searches. The analysis is conducted in the framework of two models utilizing extremum statistics: first – using the fixed grid of celestial coordinates, and second – using the tuned grid (introducing more degrees of freedom in the search). The test distributions for the significance estimation are obtained both from simulation models and from the analytical model of extremum statistics. We show that the second model gives adequate physical inference, while the first model can lead to the positively biased conclusions of the point source significance.
118030550
Comparison of GEANT4 Simulations with Testbeam Data and GEANT3 for the ATLAS Liquid Argon Calorimeter
We present several comparisons of GEANT4 simulations with test beam data and GEANT3 simulations for different liquid argon(LAr) calorimeters of the ATLAS detector,All relevant parts of the test beam setup(scintilators,multi wire proportional chambers,cryostat etc.)are described in GEANT4 as well as in GEANT3.Muon and electron data at different energies have been compared with Monte Carlo prediction.
122726428
FELIX: A Full acceptance detector at the LHC: Letter of intent
The FELIX Collaboration proposes the construction of a full acceptance detector for the LHC, to be located at Intersection Region 4, and to be commissioned concurrently with the LHC. The primary mission of FELIX is the study of QCD: to provide comprehensive and definitive observations of a very broad range of strong-interaction processes. This document contains a description of the detector concept including details of the individual detector elements and their performance characteristics, an extensive discussion of the physics menu, and the plans for integration of FELIX into the collider lattice and physical environment.
197460273
Search for Yukawa production of a light neutral Higgs boson at LEP
Within a Two-Higgs-Doublet Model (2HDM) a search for a light Higgs boson in the mass range of 4–12 GeV has been performed in the Yukawa process \(\mathrme^+ \mathrme^-\rightarrow \mathrm{b}\bar{\mathrm{b}}\mathrm{A}/\mathrm{h}\rightarrow\mathrm{b} \bar{\mathrm{b}}\tau^+\tau^-\), using the data collected by the OPAL detector at LEP between 1992 and 1995 in \(\mathrme^+ \mathrme^-\) collisions at about 91 GeV centre-of-mass energy. A likelihood selection is applied to separate background and signal. The number of observed events is in good agreement with the expected background. Within a CP-conserving 2HDM type II model the cross-section for Yukawa production depends on \(\xi^{\mathrm{A}}_d=|\tan\beta|\) and \(\xi^{\mathrm{h}}_d=|\sin\alpha/\cos\beta|\) for the production of the CP-odd A and the CP-even h, respectively, where \(\tan\beta\) is the ratio of the vacuum expectation values of the Higgs doublets and \(\alpha\) is the mixing angle between the neutral CP-even Higgs bosons. From our data 95% C.L. upper limits are derived for \(\xi^{\mathrm{A}}_d\) within the range of 8.5 to 13.6 and for \(\xi^{\mathrm{h}}_d\) between 8.2 to 13.7, depending on the mass of the Higgs boson, assuming a branching fraction into \(\tau^+\tau^-\) of 100%. An interpretation of the limits within a 2HDM type II model with Standard Model particle content is given. These results impose constraints on several models that have been proposed to explain the recent BNL measurement of the muon anomalous magnetic moment.
121450723
Single π--meson photoproduction on neutrons by linearly polarised photons in the third and fourth resonance region
The cross section asymmetry Sigma for the reaction gamma n to pi -p by linearly polarised photons was measured in the energy range Egamma =0.8-1.75 GeV and pion CM angles between 45 and 90 degrees . The results are compared with the predictions of phenomenological models.
122000305
A measurement of the energy loss spectrum of 150 GeV muons in iron
The energy loss spectrum of 150 GeV muons has been measured with a prototype of the ATLAS hadron calorimeter in the H8 beam of the CERN SPS. The differential probability ${\rm {d}}P/{\rm {d}}v$ per radiation length of a fractional energy loss $v = \Delta E_{\mu} / E_{\mu}$ has been measured in the range $v$ = 0.01 $\div$ 0.95; it is compared with the theoretical predictions for energy losses due to bremsstrahlung and production of electron-positron pairs or of energetic knock-on electrons. The integrated probability $\int_{0.01}^{0.95} ({\rm {d}}P/{\rm {d}}v) {\rm {d}}v$ is $(1.610\pm0.015_{{\rm {stat}}}\pm0.105_{{\rm {syst}}})\cdot10^{-3}$ in agreement with the theoretical predictions $1.556\cdot10^{-3}$ and $1.619\cdot10^{-3}$. Agreement with theory is also found in two intervals of $v$ where production of electron-positron pairs and knock-on electrons dominates. In the region of bremsstrahlung dominance ($v$ = 0.12 $\div$~0.95) the measured integrated probability $(1.160\pm0.040_{{\rm {stat}}}\pm0.075_{{\rm {syst}}})\cdot 10^{-4}$ is in agreement with the theoretical value of $1.185 \cdot 10^{-4} $, obtained using the Petrukhin and Shestakov description of the bremsstrahlung process. The same result is about 3.6 standard deviations (defined as the quadratic sum of statistical and systematic errors) lower than the theoretical prediction of $ 1.472\cdot 10^{-4}$, obtained using Tsai's description of bremsstrahlung.
120704929
The analysis of proton- and deuteron-induced-reaction cross sections on tin isotopes at the beam energy of 3.65 GeV/nucleon
The total inelastic cross sections of the reactions of protons and deuterons on nuclear targets of enriched tin isotopes are compared. The factorization of cross sections of reactions is discussed. Furthermore, the comparison of theoretical estimations on total inelastic cross sections with corresponding experimental ones is made.
122915783
Detection of high energy solar protons during ground level enhancements
Abstract Registration of high energy solar protons by middle and low latitude particle monitors during ground level enhancements (GLE) is investigated. We have developed a comprehensive method, for revealing weak GLE signals. The main result of the method is estimation of probability of error for given value of observed signal amplitude. We derived, that for middle energy protons, the 99% confidence limit of GLE signal detection is determined by ∼4.3 σ of observed signal, whereas for highest energy protons it is determined by ∼3.7 σ . Applying this method to GLE-65 at 28 October 2003, GLE-69 at 20 January 2005 and GLE-70 at 13 December 2006, we make conclusions about the maximal energy of protons during these events. We claim on the presence of >20…30 GeV protons in GLE-65 with the probability of error ∼7% and in the GLE-69 with the probability of error ∼0.4%. However, during GLE-70 maximal energy of protons was ∼10 GeV.