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.

title: The analysis of proton- and deuteron-induced-reaction cross sections on tin isotopes at the beam energy of 3.65 GeV/nucleon
abstract: 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.

title: Statistical methods for signal estimation of point sources of cosmic rays
abstract: 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.

title: Correlated measurements of secondary cosmic ray fluxes by the Aragats Space-Environmental Center monitors
abstract: The Aragats Space-Environmental Center provides monitoring of different species of secondary cosmic rays at two altitudes and with different energy thresholds. One-minute data is available on-line from http://crdlx5.yerphi.am/DVIN/index2.php . We present description of the main monitors along with data acquisition electronics. Also we demonstrate the sensitivity of the different species of secondary cosmic ray flux to geophysical conditions, taking as examples the extremely violent events of October–November 2003. We introduce correlation analysis of the different components of registered time-series as a new tool for the classification of the geoeffective (events on earth affected by solar activity) events and for the forecasting of the severity of the upcoming geomagnetic storm.

title: 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.

title: 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