Edgar Bugaev - Academia.edu (original) (raw)

Papers by Edgar Bugaev

Nuclear Physics B-proceedings Supplements, 1996

... 86 MM Boliev et aL /Nuclear Physics B (Proc. Suppl.) 48 (1996) 83-86 ~o lO lO :11111 I '... more ... 86 MM Boliev et aL /Nuclear Physics B (Proc. Suppl.) 48 (1996) 83-86 ~o lO lO :11111 I ' ~''"1~'" 3 _ 2 04 Figure 4. Same as Fig.3 but tan(/3) = 20 REFERENCES 1. ANTaylor and M.Rowan-Robinson. Nature 359,393 (1992) 2. J.Ellis et al. Nucl.Phys. ...

Supersymmetric models allow for stable non-topological solitons, Q-balls, which can be produced i... more Supersymmetric models allow for stable non-topological solitons, Q-balls, which can be produced in the early Universe and contribute to dark matter. Experimental signature of electrically neutral Q-balls is, in fact, the same as is expected for superheavy magnetic monopoles catalyzing baryon decay. Here we use the upper limits on monopole flux obtained with the deep underwater Cherenkov array Gyrlyanda which operated in the Baikal lake in 1984-90 with 267 days of live time to obtain the limit on Q-ball flux. The last has been found to be equal to 3.9 × 10 −16 cm −2 sr −1 s −1 (90% CL). This result is discussed and compared with other restrictions.

Physics of Atomic Nuclei, 2004

We present results of the detailed Monte Carlo calculation of the rates of double-bang events in ... more We present results of the detailed Monte Carlo calculation of the rates of double-bang events in a 1-km3 underwater neutrino telescope taking into account the effects of τ-neutrino propagation through the Earth. As an input, the moderately optimistic theoretical predictions for diffuse neutrino spectra of AGN jets are used.

The total photoabsorption cross section on the nucleon is studied using nondiagonal GVDM. Vector ... more The total photoabsorption cross section on the nucleon is studied using nondiagonal GVDM. Vector meson-nucleon scattering amplitudes are calculated in two-gluon exchange approximation of QCD. The off-diagonal transitions of diffraction dissociation type between different vector mesons and their contributions to the expression for the total photoabsorption cross section on the nucleon are also calculated. It is shown that destructive interference of diagonal and off-diagonal terms is not effective. The main conclusion is that a p-cut-off in gamma-quark antiquark transition is necessary for obtaining the convergence in the summation over all vector meson contributions.

The nondiagonal generalized vector dominance model (GVDM) of photoabsorption is elaborated using ... more The nondiagonal generalized vector dominance model (GVDM) of photoabsorption is elaborated using QCD-motivated picture of the (gamma)-(q,anti q) - transition and subsequent meson dominated scattering of the (q, anti q)-pair on the nucleon. The relativistic constituent quark model for a description of the meson (q, anti q)-wave functionsis used. The meson-nucleon scattering is calculated in the two-gluon exchange approximation. It is shown that the destructive interference effects and corresponding cancellations in the photoabsorption cross section formula are small, so the GVDM predictions are incorrect if no extra cut-off factors in GVDM formulas are introduced.

Physical Review D, 2001

We present a new Monte Carlo muon propagation algorithm MUM (MUons+Medium) which possesses some a... more We present a new Monte Carlo muon propagation algorithm MUM (MUons+Medium) which possesses some advantages over analogous algorithms presently in use. The most important features of algorithm are described. Results on the test for accuracy of treatment the muon energy loss with MUM are presented and analyzed. It is evaluated to be of 0.002 or better, depending upon simulation parameters. Contributions of different simplifications which are applied at Monte Carlo muon transportation to the resulting error are considered and ranked. It is shown that when simulating muon propagation through medium it is quite enough to account only for fluctuations in radiative energy loss with fraction of energy lost being as large as 0.05 -- 0.1. Selected results obtained with MUM are given and compared with ones from other algorithms.

Astroparticle Physics, 2004

If muon neutrinos produced in cosmological sources oscillate, neutrino telescopes can have a chan... more If muon neutrinos produced in cosmological sources oscillate, neutrino telescopes can have a chance to detect s-neutrinos. In contrast to m l s the Earth is completely transparent for m s s thanks to the short life time of s-leptons that are produced in m s N charged current interactions. s-lepton decays in flight producing another m s (regeneration chain). Thus, m s s cross the Earth without being absorbed, though loosing energy both in regeneration processes and in neutral current interactions. Neutrinos of all flavors can be detected in deep underwater/ice detectors by means of Cerenkov light emitted by charged leptons produced in m interactions. Muon and s-leptons have different energy loss features, which provide opportunities to identify s-events among the multitude of muons. Some signatures of s-leptons that can be firmly established and background free have been proposed in literature, such as 'double bang' events. In this paper we present results of Monte Carlo simulations of s-neutrino propagation through the Earth accounting for neutrino interactions, s energy losses and s decays. Parameterizations for hard part and corrections to the soft part of the photonuclear cross-section (which contributes a major part to s energy losses) are presented. Different methods of s-lepton identification in large underwater/ice neutrino telescopes are discussed. Finally, we present a calculation of m s double bang event rates in km 3 scale detectors. Cerenkov neutrino telescopes (UNTs) [1-6] would confirm oscillations already discovered at lower energies . Measuring the ratio between cosmological m l and m s fluxes one could also exclude or confirm some more exotic scenario , such as m decay, in which / ms 6 ¼ / ml . At energies E m K 1 PeV a general approach to discriminate rare neutrino events from the huge amount of atmospheric muons present also at kilometer water/ice depths is to select events from the lower hemisphere. These can be produced by neutrinos, the only known particle that can pass through the Earth with negligible absorption below these energies. Nevertheless, m cross-sections increase with energy. For muon neutrinos, absorption is considerable above 1 PeV, depending on the m zenith angle, hence on the path-length transversed in the Earth. On the other hand, m s s generate s-leptons via charged current (CC) interactions m s N ! CC sN in the Earth. Being a short-

Nuclear Physics B-proceedings Supplements, 2009

A two component model describing the electromagnetic nucleon structure functions in the low-x reg... more A two component model describing the electromagnetic nucleon structure functions in the low-x region, based on generalized vector dominance and color dipole approaches is briefly described. The model operates with the mesons of ρ-family having the mass spectrum of the form m 2 n = m 2 ρ (1 + 2n) and takes into account the nondiagonal transitions in meson-nucleon scattering. The special cut-off factors are introduced in the model, to exclude the γ − qq − V transitions in the case of narrow qq-pairs. For the color dipole part of the model the well known FKS-parameterization is used.

Possibility of a description of the photonuclear interactions of high energy muons using generali... more Possibility of a description of the photonuclear interactions of high energy muons using generalized vector dominance model (GVDM) is discussed. It is shown that the consistent GVDM scheme (i.e., the scheme which operates with more or less realistic vector mesons rather than with effective ones) alone is not able to describe the photonuclear interactions at very high energies of muons. Two-component picture of photonuclear interaction (GVDM + perturbative QCD) is proposed.

We calculated the energy spectra and the fluxes of electron neutrinos in extragalactic space emit... more We calculated the energy spectra and the fluxes of electron neutrinos in extragalactic space emitted in the process of the evaporation of primordial black holes (PBHs) in the early universe. It was assumed that PBHs are formed by a blue power-law spectrum of primordial density fluctuations. In the calculations of neutrino spectra the spectral index of density fluctuations and the reheating temperature were used as free parameters. The absorption of neutrinos during propagation in the space was taken into account. We obtained the bounds on the spectral index assuming validity of the standard picture of gravitational collapse and using the available data of several experiments with atmospheric and solar neutrinos. The comparison of our results with the previous constraints (which had been obtained using diffuse photon background data) shows that such bounds are quite sensitive to an assumed form of the initial PBH mass function.

The technical procedure of a search of bursts of very high energy gamma rays from evaporation of ... more 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 f... more 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.

Physical Review D, 2011

We perform a consistent calculation of primordial black hole (PBH) mass spectrum and second-order... more We perform a consistent calculation of primordial black hole (PBH) mass spectrum and second-order induced gravitational wave (GW) background produced from primordial scalar perturbations in radiation era of the early Universe. It is shown that the maximal amplitudes of the second-order GW spectrum that can be approached without conflicting with the PBH data do not depend significantly on the shape of primordial perturbation spectrum. The constraints on the GW background obtained in previous works are extended to a wider GW frequency range. We discuss the applicability of the currently available pulsar timing limits for obtaining the constraints on scalar power spectrum and PBH abundance and show that they can be used for strongly constraining the PBH number density in the PBH mass range ˜(0.03-10)M⊙.

Physical Review D, 2009

We calculate the primordial black hole (PBH) mass spectrum produced from a collapse of the primor... more We calculate the primordial black hole (PBH) mass spectrum produced from a collapse of the primordial density fluctuations in the early Universe using, as an input, several theoretical models giving the curvature perturbation power spectra with large (~ 0.01 - 0.1) values at some scale of comoving wave numbers k. In the calculation we take into account the explicit dependence of gravitational (Bardeen) potential on time. Using the PBH mass spectra, we further calculate the neutrino and photon energy spectra in extragalactic space from evaporation of light PBHs, and the energy density fraction contained in PBHs today (for heavier PBHs). We obtain the constraints on the model parameters using available experimental data (including data on neutrino and photon cosmic backgrounds). We briefly discuss the possibility that the observed 511 keV line from the Galactic center is produced by annihilation of positrons evaporated by PBHs.

Jetp Letters, 2010

The today’s energy density of the induced (second order) gravitational wave background in the fre... more The today’s energy density of the induced (second order) gravitational wave background in the frequency region ∼10−3–103 Hz is constrained using the existing limits on primordial black hole production in the early Universe. It is shown, in particular, that at frequencies near ∼40 Hz (which is the region explored by LIGO detector), the value of the induced part of ΩGW cannot exceed (1−3) × 10−7. The spread of values of the bound is caused by the uncertainty in parameters of the gravitational collapse of black holes.

Possibilities of an experimental search for gamma-ray bursts from primordial black hole (PBH) eva... more Possibilities of an experimental search for gamma-ray bursts from primordial black hole (PBH) evaporations in space are reconsidered. It is argued that the corresponding constraints which can be obtained in experiments with cosmic ray detectors strongly depend on theoretical approach used for a description of the PBH evaporation process. Predictions of several theoretical models for gamma-ray spectra from final stages of PBH life (integrated over time) are given.

Physical Review D, 2010

We calculate the frequency dependence of gravitational wave background arising at second order of... more We calculate the frequency dependence of gravitational wave background arising at second order of cosmological perturbation theory due to mixing of tensor and scalar modes. The calculation of the induced gravitational background is performed for two special cases: for the power spectrum of scalar perturbations which has a peak at some scale and for the scalar spectrum predicted by the inflationary model with the running mass potential. We show that the amplitudes of the induced gravitational background, in the frequency region ∼ 10 −3 − 10 3 Hz, are effectively constrained by results of studies of primordial black hole production in early universe. We argue that though today's LIGO bound on PR(k) is weaker than the PBH one, Advanced LIGO will be able to set a stronger bound, and in future the ground-based interferometers of LIGO type will be suitable for obtaining constraints on PBH number density in the mass range ∼ 10 11 − 10 15 g.

We calculate neutrino and photon energy spectra in extragalactic space from evaporation of primor... more We calculate neutrino and photon energy spectra in extragalactic space from evaporation of primordial black holes, assuming that the power spectrum of primordial density fluctuations has a strong bump in the region of small scales. The constraints on the parameters of this bump based on neutrino and photon cosmic background data are obtained.