arXiv subjects

V. Berezinsky

Publications and source records attributed to V. Berezinsky.

At least 73 records · Page 4Linked to original sources

arXiv1999

Solar neutrino fluxes with arbitrary He3 mixing

The He3 abundance is not constrained by helioseismic data. Mixing of He3 inside the solar core by processes not included in the solar standard model (SSM) has been recently proposed as possible solution to the solar neutrino problem. We have performed a model independent analysis of solar neutrino fluxes using practically arbitrary He3 mixing. In addition, we have been simultaneously varying within very wide ranges the temperature in the neutrino production zone and the astrophysical factors, S17 and S34, of the p+Be7 and He3+He4 cross sections. Seismic data are used as constraints, but the solar- luminosity constraint is not imposed. It is demonstrated that even allowing He3 abundances higher by factors up to 16 than in the SSM, temperatures 5% (or more) lower, the astrophysical factor S17 up to 40% higher, and varying S34 in the range (-20% ,+40%), the best fit is still more than 5 sigmas away from the observed fluxes. We conclude that practically arbitrary He3 mixing combined with independent variations of temperature and cross-sections cannot explain the observed solar neutrino fluxes.

astro-ph↗

arXiv1999

Ultra high energy neutrinos from hidden-sector topological defects

We study Topological Defects (TD) in hidden (mirror) matter as possible sources of ultra-high energy neutrinos. The hidden/mirror and ordinary matter are assumed to interact very weakly through gravity or superheavy particles. An inflationary scenario is outlined in which superheavy defects are formed in hidden/mirror matter (and not in ordinary matter), and at the same time the density of mirror matter produced at the end of inflation is much smaller than that of ordinary matter. Superheavy particles produced by hidden-sector TD and the products of their decays are all sterile in our world. Only mirror neutrinos oscillate into ordinary neutrinos. We show that oscillations with maximal mixing of neutrinos from both worlds are possible and that values of $Δm^2$, needed for for solution of solar-neutrino and atmospheric-neutrino problems, allow the oscillation of ultra-high energy neutrinos on a timescale of the age of the Universe. A model of mass-degenerate visible and mirror neutrinos with maximal mixing is constructed. Constraints on UHE neutrino fluxes are obtained. The estimated fluxes can be 3 orders of magnitude higher than those from ordinary matter. Detection of these fluxes is briefly discussed.

hep-ph↗

arXiv1999

Oscillation Solutions to Solar Neutrino Problem

The current status of oscillation solutions to the Solar Neutrino Problem is reviewed. Four oscillation solutions are discussed in the light of 708d Superkamiokande data: MSW, Just-So VO, VO with Energy-Independent Suppression (EIS) and Resonant-Spin-Flavor-Precession (RSFP). Only EIS VO is strongly disfavoured by the global rates, mostly due to the Homestake data. Vacuum oscillations give an interesting solution which explains high-energy excess of events observed by Superkamiokande and predicts {\em semi-annual} seasonal variation of $Be$-neutrino flux. There are indications to these variations in the GALLEX and Homestake data. No direct evidence for oscillation is found yet.

hep-ph↗

arXiv1999

Anisotropy of Ultra High Energy Cosmic Rays in the Dark Matter Halo Model

The harmonic analysis of anisotropy of Ultra High Energy Cosmic Rays is performed for the Dark Matter halo model. In this model the relic superheavy particles comprise part of the Dark Matter and are concentrated in the Galactic halo. The Ultra High Energy Cosmic Rays are produced by the decays of these particles. Anisotropy is caused by the non-central position of the Sun in the Galactic halo. The calculated anisotropy is in reasonable agreement with the AGASA data. For more precise test of the model a comparison of fluxes in the directions of the Galactic Center and Anticenter is needed.

astro-ph↗

arXiv1998

Vacuum oscillations and the distorted solar neutrino spectrum observed by Superkamiokande

The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by vacuum oscillations (VO). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.5 sigmas) higher than the measured one, there exists a VO solution that reproduces both the observed boron neutrino spectrum, including the high energy distortion, and the other measured neutrino rates. This solution might already be testable by the predicted anomalous seasonal variation of the gallium signal. Its most distinct signature, a large anomalous seasonal variation of Be7 neutrino flux, can be easily observed by the future detectors, BOREXINO and LENS.

hep-ph↗

arXiv1998

Ultra high energy cosmic rays from cosmological relics

Ultra High Energy Cosmic Rays (UHECR) can be a signal from very early (post-inflationary) Universe. At this cosmological epoch Topological Defects (TD) and long-lived suprheavy (SH) particles are expected to be naturally and effectively produced. Both of these relics can produce now the particles, such as protons and photons, with energies in a great excess of what is observed in UHECR, $E \sim 10^{10} - 10^{11} GeV$. The Topological Defects as the UHECR sources are critically reviewed and cosmic necklaces and monopolonia are identified as most plausible sources. The relic superheavy particles and monopolonia are shown to be clustering in the halo of our Galaxy and their decays produce UHECR without the GZK cutoff. The observational signature of both models are discussed.

astro-ph↗

arXiv1998

Bounds on hep neutrinos

The excess of highest energy solar-neutrino events recently observed by Superkamiokande can be in principle explained by anomalously high $hep$-neutrino flux $Φ_ν(hep)$. Without using SSM calculations, from the solar luminosity constraint we derive that $Φ_ν(hep)/S_{13}$ cannot exceed the SSM estimate by more than a factor three. If one makes the additional hypothesis that $hep$ neutrino production occurs where the $^3$He concentration is at equilibrium, helioseismology gives an upper bound which is (less then) two times the SSM prediction. We argue that the anomalous $hep$-neutrino flux of order of that observed by Superkamiokande cannot be explained by astrophysics, but rather by a large production cross-section.

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arXiv1998

Limiting SUSY-QCD spectrum and its application for decays of superheavy particles

The supersymmetric generalization of the limiting and Gaussian QCD spectra is obtained. These spectra are valid for $x \ll 1$, when the main contribution to the parton cascade is given by gluons and gluinos. The derived spectra are applied to decaying superheavy particles with masses up to the GUT scale. These particles can be relics from the Big Bang or produced by topological defects and could give rise to the observed ultrahigh energy cosmic rays. General formulae for the fluxes of protons, photons and neutrinos due to decays of superheavy particles are obtained.

hep-ph↗

arXiv1998

Ultra High Energy Cosmic Rays

The current status of Ultra High Energy Cosmic Rays (UHECR) is reviewed, with emphasis given to theoretical interpretation of the observed events. The galactic and extragalactic origin, in case of astrophysical sources of UHE particles, have the problems either with acceleration to the observed energies or with the fluxes and spectra. Topological defects can naturally produce particles with energies as observed and much higher, but in most cases fail to produce the observed fluxes. Cosmic necklaces and monopole-antimonopole pairs are identified as most plausible sources, which can provide the observed flux and spectrum. The relic superheavy particles are shown to be clustering in the Galactic halo, producing UHECR without Greisen-Zatsepin-Kuzmin cutoff. The Lightest Supersymmetric Particles are discussed as UHE carriers in the Universe.

hep-ph↗

arXiv1998

Ultra High Energy Cosmic Rays from Decaying Superheavy Particles

Decaying superheavy particles can be produced by Topological Defects or, in case they are quasi-stable, as relics from the early Universe. The decays of these particles can be the sources of observed Ultra High Energy Cosmic Rays ($E \sim 10^{10} - 10^{12} GeV$). The Topological Defects as the UHE CR sources are critically reviewed and cosmic necklaces and monopole-antiminopole pairs are identified as most plausible sources. The relic superheavy particles are shown to be clustering in the halo and their decays produce UHE CR without GZK cutoff. The Lightest Supersymmetric Particles with Ultra High Energies are naturally produced in the cascades accompanying the decays of superheavy particles. These particles are discussed as UHE carriers in the Universe.

astro-ph↗

arXiv1997

Solar neutrinos as highlight of astroparticle physics

Solar neutrinos are discussed in the light of the new data and of recent progress in helioseismology. Most attention is given to the new status of Standard Solar Models due to seismically measured density and sound speed in the inner solar core. The elementary particle solutions to the Solar Neutrino Problem and their observational signatures are discussed.

astro-ph↗

arXiv1997

Ultra-high energy LSP

We argue that the lightest supersymmetric particles (LSP) can be produced with extremely high energies $E\gsim 10^{10}$ GeV in the Universe at the present epoch. Their most probable sources are decaying superheavy particles produced by topological defects or as relic Big Bang particle. We discuss the mechanisms of production of LSP at ultra-high energies (UHE) and the interaction of the UHE LSP with matter. The most attention is given to the neutralino as LSP, although the gluino is also considered as a phenomenological possibility.

hep-ph↗

arXiv1997

Ultra-high energy cosmic rays without GZK cutoff

We study the decays of ultraheavy (m_X \geq 10^{13}GeV) and quasistable (lifetime τ_X much larger than the age of the Universe t_0) particles as the source of Ultra High Energy Cosmic Rays (UHE CR). These particles are assumed to constitute a tiny fraction ξ_X of CDM in the Universe, with ξ_X being the same in the halo of our Galaxy and in the intergalactic space. The elementary-particle and cosmological scenarios for these particles are briefly outlined. The UHE CR fluxes produced at the decays of X- particles are calculated. The dominant contribution is given by fluxes of photons and nucleons from the halo of our Galaxy and thus they do not exibit the GZK cutoff. The extragalactic components of UHE CR are suppressed by the smaller extragalactic density of X-particles and hence the cascade limit is relaxed. We discuss the spectrum of produced Extensive Air Showers (EAS) and a signal from Virgo cluster as signatures of this model.

astro-ph↗

arXiv1997

Helioseismic constraints to the central solar temperature and neutrino fluxes

The central solar temperature T and its uncertainties are calculated in helioseismologically-constrained solar models. From the best fit to the convective radius, density at the convective radius and seismically determined helium abundance the central temperature is found to be T=1.58x10^7 K, in excellent agreement with Standard Solar Models. Conservatively, we estimate that the accuracy of this determination is Delta T/T=1.4 %, better than that in SSM. Neutrino fluxes are calculated. The lower limit to the boron neutrino flux, obtained with maximum reduction factors from all sources of uncertainties, is 2 sigma higher than the flux measured recently by SuperKamiokande.

astro-ph↗

arXiv1997

50 TeV HEGRA Sources and Infrared Radiation

The recent observations of 50 TeV gamma radiation by HEGRA have the potential of determining the extragalactic flux of infrared radiation. The fact that radiation is observed in the range between 30 and 100 TeV sets an upper limit on the infrared flux, while a cutoff at $E_γ \approx 50$ TeV fixes this flux with a good accuracy. If the intrinsic radiation is produced due to interaction of high energy protons with gas or low-energy target photons, then an accompaning high-energy neutrino flux is unavoidable. We calculate this flux and underground muon flux produced by it. The muon flux is dominated by muons with energies about 1 TeV and can be marginally detected by a 1 km$^2$ detector like an expanded AMANDA.

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arXiv1996

New Trends in Solar-Neutrino Physics

These are the Proceedings of the 4th discussion workshop in the Gran Sasso Laboratory. The structure of this workshop was as before: most of the time was allocated to the review talks and to the discussions. There were discussion sessions and short original presentations for each topic as well as the general discussion session at the end of the workshop.

astro-ph↗

arXiv1996

Dark matter particles

The baryonic and cold dark matter are reviewed in the context of cosmological models. The theoretical search for the particle candidates is limited by supersymmetric extension of the Standard Model. Generically in such models there are just two candidates associated with each other: generalized neutralino, which components are usual neutralino and axino, and axion which is a partner of axino in supermultiplet. The status of these particles as DM candidates is described.

astro-ph↗

arXiv1996

On neutralino stars as microlensing objects

The microlensing objects, Machos, recently observed in the halo of our Galaxy, can be interpreted as dense neutralino objects, neutralino stars, produced by the gravitational instability of neutralino gas. Taking the mass and radius of these objects from microlensing observations we calculated the diffuse gamma-ray flux produced in neutralino--neutralino annihilation inside the objects. The resulting flux is many orders of magnitude higher than the observed one.

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