Search

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

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.

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.

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 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

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

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 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.