arXiv subjects
Publications and source records attributed to V. B. Petkov.
Current status and results of the experiment on recording neutrino bursts are presented. The observation time (since 1980) is 24.7 years. The upper bound of collapse frequency in our Galaxy is 0.093 $y^{-1}$ (90% CL).
The technical procedure of a search of bursts of very high energy gamma rays from evaporation of primordial black holes on air-shower array "Andyrchy" of Baksan Neutrino Observatory of Institute for Nuclear Research is described. The theoretical model used in the present work assumes that the chromosphere around the evaporating black hole does not form. For minimization of the cosmic ray background the method of multidimensional analysis of modelled as well as experimentally detected events is applied. The new upper limit on the concentration of evaporating primordial black holes in the local region of Galaxy is obtained. The comparison of the results of different experiments is given.
Experimental data of arrays "Andyrchy" and "Carpet-2" of Baksan Neutrino Observatory (Institute for Nuclear Research), obtained in the regime of a detection of the single cosmic-ray component, are used for a search of the bursts of cosmic gamma rays from evaporating primordial black holes. Different theoretical models of the evaporation process are used for the analysis. Distributions of the counting rate fluctuations on both arrays agree with the expectations from the cosmic ray background. The new constraints on the concentration of evaporating primordial black holes in the local region of Galaxy are obtained. The comparison of the results of different experiments is given.
The lateral distribution function of high energy muons in EAS around the knee ($5.9\le \lg N_e \le 7.1$) has been measured for near vertical showers ($θ\le 20^{\circ}$, effective muon threshold energy is 230 GeV). The measurements have been performed at the Baksan Underground Scintillation Telescope (BUST). The electromagnetic component is measured by the "Andyrchy" EAS array, located above the BUST. The knee in EAS size spectrum is found to be at $\lg N_e \approx 6.3$. The experimental results are compared with Monte Carlo simulations.
The results of a development of a scintillator counter with wavelength shifting (WLS) fibre and a multi-pixel Geiger-mode avalanche photodiode readout are presented. The photodiode has a metal-resistor-semiconductor layered structure and operates in the limited Geiger mode. The scintillator counter has been developed for the EMMA underground cosmic ray experiment.
In this short note we present results of background measurements carried out with a polystyrene based cast plastic 12.0x12.0x3.0 cm^3 size scintillator counter with a wavelength shifting fibre and a multi-pixel Geiger mode avalanche photodiode readout in the Baksan underground laboratory at a depth of 200 meters of water equivalent. The total counting rate of the scintillator counter measured at this depth and at a threshold corresponding to ~0.37 of a minimum ionizing particle is approximately 1.3 Hz.
Temporal and energy characteristics of the very-high-energy gamma-ray bursts from evaporating primordial black holes have been calculated by assuming that the photospheric and chromospheric effects are negligible. The technique of searching for such bursts on shower arrays is described. We show that the burst time profile and the array dead time should be taken into account to interpret experimental data. Based on data from the Andyrchy array of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences), we have obtained an upper limit on the number density of evaporating primordial black holes in a local region of space with a scale size of ~10^{-3} pc. Comparison with the results of previous experiments is made.
Cosmic gamma-ray bursts with primary-photon energies > 10 GeV are sought in the data from the Andyrchy array obtained in the mode of detection of a single cosmic-ray component during a net observation period of 2005.4 d. The distribution of fluctuations of the detector counting rate agrees with the expected cosmic-ray background, the only exception being an event with a deviation of 7.9 sigma. Constraints on the number density of evaporating primordial black holes in a local region of the Galaxy are obtained for the chromospheric evaporation models.
22 Sep 2005 Swift-BAT triggered and located GRB050922C. The light curve shows the intense broad peak with $T_{90}$ of $(5 \pm 1)$ s. The Nordic Optical Telescope has obtained spectra of the afterglow with several absorption features corresponding to a redshift of $z = 2.17 \pm 0.03$. Observation of optical transient of GRB050922C was carried out in the R-band with the 60-cm telescope equipped with a CCD on Peak Terskol (North Caucasus). The OT magnitude was fading from R $\approx 16$ to $\approx 17.5$. Detection of an oscillatory phenomenon in the R post-burst light curve is described in this work. Analysis of the R data reveals coherent harmonic with a period of $0.0050 \pm 0.0003$ days (7.2 min) during observing run of about 0.05 days ($\sim 70$ min). Amplitude of oscillations is about 0.05 magnitude. The simplest model suggests that GRB050922C may result from tidal disruption of a white dwarf star by a black hole of about one thousand solar mass. The periodicity in the light curve can be identified with relativistic precession of an accretion disc.
The results of measuring diurnal variations of extensive air showers with energy above 100 TeV detected by the Andyrchi air shower array in 1995-2002 are presented. It is shown that solar diurnal wave of intensity is formed by pressure variations and Compton-Getting effect (due to the orbital motion of the Earth). The data on cosmic ray anisotropy of the Baksan underground scintillation telescope (BUST) are also presented for energies above 2.5 TeV covering the period 1982-1998. The diurnal sidereal wave measured by both Andyrchi and BUST is due to anisotropy of the cosmic rays.
The estimation of light velocity dispertion caused by quantum fluctuations influence on electromagnetic wave propogation in four-dimensional space-time is presented. Analytical cosmological solutions for the flat and open Universe for the case of cosmic vacuum model are obtained. The time delay of cosmic gamma-ray burst radiation is calculated. The delay is explained by propogation of dispersive electromagnetic wave in the expanding Universe. It is shown that the delay value depends on a model of the Universe. We conclude that to discern a model of the Universe measurement accuracy of parameter Δt / ΔE_γ should be better than 10^{-5} s / MeV.
We present the experimental data on the knee, as observed in the electromagnatic and high energy muon (Eμ\ge 230 Gev) components.