Search

Investigation of lepton propagation through matter is of importance for cosmic-ray physics and neutrino astronomy. The diffractive scattering of virtual photons is considered as a process that leads to the energy loss of leptons emitting these photons. The interference between this process and bremsstrahlung makes a contribution that depends on the sign of the lepton charge.

Nuclear shadowing corrections to the structure functions of deep inelastic scattering on intermediate-mass nuclei are calculated at very small values of Bjorken x and small values of Q^2 (Q^2, 12 pages, 8 figures

Primordial black holes (PBHs) are black holes which may form in the early Universe through the gravitational collapse of primordial cosmological density fluctuations. Due to Hawking radiation these PBHs are supposed to evaporate by emitting particles. Recent developments in the experimental searching for evaporating PBHs in the local Universe are reviewed. The multimessenger techniques of searching for signals from evaporating PBHs are discussed.

The energy spectra and temporal characteristics of high-energy gamma-ray bursts from evaporating primordial black holes have been calculated using various evaporation models. The currently existing theoretical uncertainties in the shape of the evaporated photon spectrum are discussed. The data from the Andyrchy and Carpet-2 arrays of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) obtained in the mode of detection of a single cosmic-ray component are used to search for cosmic gamma-ray bursts with a primary photon energy of about 8 GeV. New upper limits have been obtained for the number density of evaporating black holes in a local region of space with a characteristic size of ∼10−3 pc for various evaporation models.

It is shown that experimental data on the electromagnetic structure functions of a nucleon in the kinematic region of low x can be described in terms of a two-component approach in which the nonperturbative part of photon-nucleon interaction is described in terms of a updated variant of the generalized model of vector dominance that includes the radial excitations of mesons and off-diagonal elements of the matrix of meson-nucleon scattering. The perturbative component is described using the color-dipole model.

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 n 2 = m ρ 2 ( 1 + 2 n ) 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 − q q ¯ − V transitions in the case of narrow q q ¯ -pairs. For the color dipole part of the model the well known FKS-parameterization is used.

We consider the inflationary model in which the inflaton $\phi$ couples to another scalar field $\chi$ via the interaction $g^2(\phi-\phi_0)^2\chi^2$ with a small coupling constant $g$ ($g^2 \sim 10^{-7}$). We assume that there is a sequence of "trapping points" $\phi_{0i}$ along the inflationary trajectory where particles of $\chi$-field become massless and are rather effectively produced. We calculate the power spectrum of inflaton field fluctuations originated from a backreaction of $\chi$-particles produced, using the Schwinger's "in-in" formalism. We show that the primary curvature power spectrum produced by these backreaction effects is blue, which leads to a strong overproduction of primordial black holes (PBHs) in subsequent radiation era., Comment: v2: 14 pages, 5 figures, version accepted by Phys. Rev. D

Photonuclear interactions of super-high energy leptons are studied. The consideration is based on a two-component model of the inelastic lepton-nucleon scattering in the diffractive region proposed by authors. Parameters of the model are chosen by comparison of the model's predictions for electromagnetic structure functions of a nucleon with DESY data. Results of numerical calculations of photonuclear cross sections for muons and tau-leptons of super-high energies ( up to 10 9 GeV )and of the corresponding energy loss coefficients are presented.

We argued that deep inelastic scattering (DIS) at small values of Q squared is an essentially nonperturbative process and can be described, partially at least, by the vector meson dominance (VMD) model. We showed by the straightforward calculation that VMD model alone can successfully explain data on structure functions of DIS in a broad interval of x (5e-2 - 1e-4) for the region Q squared < 1 GeV squared. For a description of data at larger Q squared we used the two-component (VMD + perturbative QCD) approach. We showed that these two components can be separated if VMD is used in the aligned jet version. We took into account, in calculations of VMD component of structure functions, the excited states of the rho-meson and nondiagonal transitions between different members of the rho-meson family. Amplitudes of these transitions were obtained using a formalism of the light-front Bethe-Salpeter equation and the method of diffraction-scattering eigenstates. The perturbative QCD component was calculated using a framework of the colour dipole model with the dipole cross section having a Regge-type energy dependence. We presented results of the detailed comparison of our predictions with experimental data for structure functions of the nucleon. We obtained also approximate predictions for the structure functions in the region of very small x, up to 1e-9, and showed that nonperturbative component at such values of x is still relatively large and must be taken into account if Q squared is about few GeV squared or less.

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 count rate agrees with the expected cosmic-ray background, the only exception being an event with a deviation of 7.9σ. Constraints on the number density of evaporating primordial black holes in a local region of the Galaxy are obtained for the chromospheric evaporation models.

The cross section for high energy muon bremsstrahlung on heavy atoms is calculated without the use of the Born approximation. It is shown that the correction to the Born approximation in the region of momentum transfers $q$ of the order of $\ensuremath{\mu}c$ has the same order of magnitude as the well-known correction of Davies, Bethe, and Maximon. It is shown also that these corrections have different signs and nearly compensate each other.

We study the process of primordial black hole (PBH) formation at the beginning of radiation era for the cosmological scenario in which the inflaton is a pseudo-Nambu-Goldstone boson (axion) and there is a coupling of the inflaton with some gauge field. In this model inflation is accompanied by the gauge quanta production and a strong rise of the curvature power spectrum amplitude at small scales (along with non-Gaussianity) is predicted. We show that data on PBH searches can be used for a derivation of essential constraints on the model parameters in such an axion inflation scenario. We compare our numerical results with the similar results published earlier, in the work by Linde et al., Comment: v2: 18 pages, 5 figures. Revised version of the paper accepted for publication in Phys.Rev.D

We consider the mixed inflaton-curvaton scenario in which quantum fluctuations of the curvaton field during inflation lead to a relatively large curvature perturbation spectrum at small scales. We use the model of chaotic inflation with quadratic potential including supergravity corrections leading to a large positive tilt in the power spectrum of the curvaton field. The model is characterized by the strongly inhomogeneous curvaton field in the Universe and large non-Gaussianity of curvature perturbations at small scales. We obtained the constraints on the model parameters considering the process of primordial black hole (PBH) production in radiation era., v2: 11 pages, 5 figures. Extended version accepted by Phys. Rev. D

We show that nucleon electromagnetic structure functions of deep inelastic scattering in Regge-Gribov limit (fixed Q-squared, asymptotically large 1/x and s) can be well described in the two-component (soft + hard) approach. In the concrete model elaborated by authors, the soft part of the virtual photon-nucleon scattering is given by the vector meson dominance, with taking into account the radial excitations of the rho-meson and nondiagonal transitions in meson-nucleon interactions. The hard part is calculated by using the dipole factorization, i.e., the process is considered as the dissociation of the photon into a q and anti-q - pair (the "color dipole") and the subsequent interaction of this dipole with the nucleon. The dipole cross section has a Regge-type s-dependence and vanishes in the limit of large transverse sizes of the dipole. We give the brief description of the model and present results of the detailed comparison of model predictions with experimental data for electromagnetic structure functions of the nucleon., 6 pages, 4 figures, the revised version prepared for a publication in Proceedings of 23rd European Cosmic Ray Symposium

We consider the process of primordial black hole (PBH) formation originated from primordial curvature perturbations produced during waterfall transition (with tachyonic instability), at the end of hybrid inflation. It is known that in such inflation models, rather large values of curvature perturbation amplitudes can be reached, which can potentially cause a significant PBH production in the early Universe. The probability distributions of density perturbation amplitudes in this case can be strongly non-Gaussian, which requires a special treatment. We calculated PBH abundances and PBH mass spectra for the model, and analyzed their dependence on model parameters. We obtained the constraints on the parameters of the inflationary potential, using the available limits on $\beta_{PBH}$., Comment: v2: 11 pages, 4 figures. Several comments and references added. Version accepted by Phys. Rev. D

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., 3 pages, 1 figure, Talk given at the 14th Lomonosov Conference, Moscow, August 2009

We carried out numerical calculations of a contribution of the waterfall field to the primordial curvature perturbation (on uniform density hypersurfaces) $\zeta$, which is produced during waterfall transition in hybrid inflation scenario. The calculation is performed for a broad interval of values of the model parameters. We show that there is a strong growth of amplitudes of the curvature perturbation spectrum in the limit when the bare mass-squared of the waterfall field becomes comparable with the square of Hubble parameter. We show that in this limit the primordial black hole constraints on the curvature perturbations must be taken into account. It is shown that, in the same limit, peak values of the curvature perturbation spectra are far beyond horizon, and the spectra are strongly non-Gaussian., Comment: v2: 16 pages, 6 figures. Several references and 1 figure added

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 $\sim (0.03 - 10) M_{\odot}$., 10 pages, 4 figures. v2 - revised version, accepted for publication in Phys. Rev. D

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.

We study, by numerical methods, the time evolution of scalar perturbations in radiation era of Randall-Sundrum braneworld cosmology. Our results confirm an existence of the enhancement of perturbation amplitudes (near horizon crossing), discovered recently. We suggest the approximate solution of equations of the perturbation theory in the high energy regime, which predicts that the enhancement factor is asymptotically constant, as a function of scale. We discuss the application of this result for the problem of primordial black hole production in braneworld cosmology., Comment: 12 pages, 8 figures

We describe the lake Baikal deep underwater detector “NT-200” and discuss its physics capabilities to investigate problems in the field of neutrino astrophysics, cosmic ray physics and particle physics.

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 $\sim 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 ${\cal P}_{\cal R}(k)$ 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 $\sim 10^{11} - 10^{15}$ g., v2: 14 pages, 7 figures; revised version of the manuscript, accepted for publication in Phys. Rev. D

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., Comment: 6 pages, 6 figures

We consider the examples of single-field inflation models predicting large amplitudes of the curvature perturbation power spectrum at relatively small scales. It is shown that in models with an inflationary potential of double-well type the peaks in the power spectrum, having, in maximum, the amplitude ~0.1, can exist (if parameters of the potential are chosen appropriately). It is shown also that the spectrum amplitude of the same magnitude (at large k values) is predicted in the model with the running mass potential, if the positive running, n', exists and is about 0.005 at cosmological scales. Estimates of the quantum diffusion effects during inflation in models with the running mass potential are given., Comment: 10 pages, 12 figures. In v3, minor modifications were made to match version accepted by Phys. Rev. D: length of the introduction reduced, several references added

We consider the modification of extragalactic cosmic ray spectrum caused by cosmic ray interactions with infrared background photons which are present in the extragalactic space together with relic photons. It is assumed that cosmic ray spectrum at superhigh energies has extragalactic origin and is proton dominated., Talk given at the NANP'05 conference, June 2005. 5 pages, one eps figure

If muon neutrinos produced in cosmological sources oscillate, neutrino telescopes can have a chance to detect tau-neutrinos. In contrast to muon neutrinos the Earth is completely transparent for tau neutrinos thanks to the short life time of tau-leptons produced in charged current interactions. Tau-lepton decaysin flight producing another tau neutrino (regeneration chain). Thus, tau neutrinos 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 Cherenkov light emitted by charged leptons produced in neutrino interactions. Muon and tau-leptons have different energy loss features, which provide opportunities to identify tau-events among the multitude of muons. Some signatures of tau-leptons that can be firmly established and are background free have been proposed in literature, such as 'double bang' events. In this paper we present results of Monte Carlo simulations of tau-neutrino propagation through the Earth accounting for neutrino interactions, tau energy losses and tau decays. Parameterizations for hard part and corrections to the soft part of the photonuclear cross-section (which contributes a major part to tau energy losses) are presented. Different methods of tau-lepton identification in large underwater/ice neutrino telescopes are discussed. Finally, we present a calculation of tau neutrino double bang event rates in cubic km scale detectors., Comment: 29 pages, 14 figures, uses elsart.cls, elsart.sty, elsart12.sty, accepted by Astroparticle Physycs on March 20th, 2004

We present results of the detailed Monte Carlo calculation of the rates of double-bang events in 1 km$^3$ underwater neutrino telescope with taking into account the effects of $\tau$-neutrino propagation through the Earth. As an input, the moderately optimistic theoretical predictions for diffuse neutrino spectra of AGN jets are used., Comment: Talk given at the NANP'03 conference, June 2003. 4 pages, one eps figure

General formalism for a two-component description of the inelastic lepton-nucleon scattering in the diffractive region is proposed. Nonperturbative contribution to electromagnetic structure functions of a nucleon is described by the modified generalized vector dominance model containing special cut-off factors restricting the phase volume of initial qq-pairs of virtual photon's fluctuations. Perturbative QCD contribution is described by the phenomenological model suggested (in nonunitarized form) by Forshaw, Kerley and Shaw. Formulae needed for a numerical calculation of photonuclear cross sections integrated over Q^2 are presented. It is argued that in a case of the photonuclear cross sections at superhigh energies of leptons (E>=10^6GeV), integrated over Q^2, the following two-component scheme is good enough: the nonperturbative contribution is approximated by the old parameterization of Bezrukov and Bugaev, and perturbative one is described by the model of Forshaw, Kerley and Shaw with parameters determined from DESY data. Corresponding results of numerical calculations of the perturbative part, for the cases of muon and tau-lepton scattering at superhigh energies, are given., 30 pages, which includes 9 figures. In this new version we corrected the error in the fig.9

The analytical expression for angular integral flux of atmospheric muons in matter with the explicit relation of its parameters with those of the sea level spectrum is obtained. The fitting formula for the sea level muon spectrum at different zenith angles for spherical atmosphere is proposed. The concrete calculations for pure water are presented. Fluctuations of muon energy losses are taken into account by means of parametrized correction factor calculated using survival probabilities resulted from Monte Carlo simulations. Parametrizations of all continuous energy losses are obtained with using the most recent expressions for muon interaction cross-sections. The corresponding parametrization errors and field of method application are comprehensively discussed. The proposed formulae could be useful primarily for experimentalists processing data of arrays located deep under water or under ice.

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., 24 pages, 15 .eps figures, uses aps.sty, aps10.sty, prabib.sty, revtex.sty. The preprint has been essentially changed and joined with hep-ph/0010323 in the frame of preparation for publication in Physical Review D

We calculated the energy spectra and the fluxes of electron neutrino emitted in the process of 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. We obtained the bounds on the spectral index of density fluctuations 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., 18 pages,(with 7 figures)

The deep underwater Cherenkov neutrino telescope NT-200 is currently under construction at Lake Baikal. The "subdetectors" NT-36 (1993-95) and NT-72 (1995-96) have been operating successfully over 3 years. Various techniques have been developed to search for magnetic monopoles with these arrays. Here we describe a method used to detect superheavy slowly moving (beta = v/c = 0.00001 - 0.001) monopoles catalyzing baryon decay. We present results obtained from the preliminary analysis of the data taken with NT-36 detector in 1993. Furthermore, possibilities to observe faster (beta = 0.2 - 1) monopoles via other effects are discussed.

Energy spectra and zenith-angle distributions of cosmic-ray muons, neutrinos and antineutrinos of prompt generation for energy interval (1÷106) TeV are calculated. For calculations of differential cross-sections of D±, D0,\(\bar D\)0 and Λc production inNN and πN interactions the recombination quark-parton model (RQPM) is used. Accounting of nuclear effects is done by using the additive quark model and the optical model of nucleus. Detailed comparison of results obtained in RQPM with corresponding predictions of quark-gluon string model (MQGS) is carried out. Dynamics of semi-leptonic D- and Λc and energy losses of muons in the atmosphere are taken into account. Calculations of hadronic cascades in the atmosphere are done with accounting of growth with energy of total inelastic hadron-nucleus cross-sections, steepening of primary cosmic-ray spectrum and processes of pion regeneration. The comparison of our calculations with experimental data and with calculations of other authors is given.

The comparison between the KAMIOKANDE data and theoretical estimations of the low-energy ( E ν of ν e ↔ ν μ - type predominantly ), or by misidentifying the particle species of single-ring events.