119020922
Investigation of induced fission of natPb by accelerated 7Li ions
Cross-sections for fragments produced by the fission reaction induced by accelerated 7Li ions impinged into an natPb target at 245MeV were obtained. We have applied the induced-activation method in off-line analysis. The analysis of charge and mass distributions of fission products allowed the determination of the total fission cross-section for the 7Li+Pb system. The recoil technique (“thick target - thick catcher”), based on the two-step model mathematical formalism, is used to determine the kinematics characteristics of reaction products. The analysis concerning transferred linear momentum provided information on the initial projectile-target interaction, and is compared with proton-induced fission measurements.
119300484
Fission of pre-actinide nuclei
A study of photofission on 181Ta nucleus induced by bremsstrahlung photons with endpoint energies of 50 and 3500 MeV has been performed. The fission yields have been measured by using the induced-activity method in an off-line analysis. The absolute photofission cross sections for the tantalum target at 50 and 3500 MeV are found to be 5.4 \pm 1.1 microb and 0.77\pm0.11 mb, respectively, and the corresponding deduced fissilities are (0.23\pm0.05) x 10^{-3} and (2.9 \pm 0.9) x 10^{-3}. Mass- and charge-yield distributions were derived from the data. The results were compared with the simulated results from CRISP code for multi-modal fission by assuming symmetrical fission mode.
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.
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.
120745631
Investigation of cosmic ray anisotropy based on Tsumeb neutron monitor data
Abstract We investigate sidereal daily variations of galactic cosmic rays (CR) by using Tsumeb neutron monitor’s (NM) hourly count during 1977–2000. For that purpose a special data analysis is applied to remove solar induced daily variations and improve sidereal variations. Then, the declination of protons in the Earth’s magnetosphere is analyzed for the proper determination of particles’ asymptotic directions. As a result we found ∼0.07% anisotropy with an excess flux from the direction of the right ascension (RA) ∼6 h. The reversal of solar magnetic field from the negative polarity state (in the time interval 1977–1989) to the positive state (in the interval 1990–2000) does not decrease the amplitude of anisotropy, which means that the origin of anisotropy found is “heliospheric” and not “galactic”. We conclude that the observed anisotropy is a tail-in anisotropy , which has been discovered earlier for higher energy (150 GeV–10 TeV) particles in several experiments with underground muon monitors and air-shower detectors. It is believed that the tail-in anisotropy is caused by heliotail boundary, located in the direction RA ∼6 h, where the interaction between galactic and solar magnetic fields produces CR acceleration
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.
123495063
Directivity function of muon detector
Abstract We introduce a new concept of directivity function (DF) to describe directional sensitivity of a particle detector. DF is а 3D function, describing the sensitivity of a detector to asymptotic directions of primary protons. It defines the contribution of primary protons, arriving from different asymptotic directions to the count rate of the detector. We develop the approach for computing the DF and derive it in particular case of SEVAN muon detector, located at mount Aragats, Armenia. Obtained data enable one to outline the region of solid angles, inside of which the arriving protons contribute a given percentage of count rate. In general, the DF can have the multi peak shape. It provides the most detailed and accurate description of directional sensitivity of a particle detector and we suggest that it is used in space research based on neutron and muon detectors.
119078457
Advanced configuration of gravitational-wave interferometer on the base of “sensitive mode” in “white-light cavity”
Abstract A novel conception of “sensitive mode” (SM) is proposed to apply in gravitational-wave advanced interferometer configuration (AIC). The SM is resonant oscillation of electromagnetic field in “white-light cavity”, where the resonance line is broadened without decreasing cavity quality. The resonant field frequency of the SM is greatly susceptible to the change of cavity length, and the SM is established in a cavity with time constant smaller than a conventional mode. Due to these advantages the sensitivity and bandwidth of AIC can be increased.