arXiv subjects

V. Berezinsky

Publications and source records attributed to V. Berezinsky.

81 records · Page 5Linked to original sources

arXiv1996

Gravitational Violation of R Parity and its Cosmological Signatures

The discrete R-parity ($R_P$) usually imposed on the Supersymmetric (SUSY) models is expected to be broken at least gravitationally. If the neutralino is a dark matter particle its decay channels into positrons, antiprotons and neutrinos are severely constrained from astrophysical observations. These constraints are shown to be violated even for Planck-mass-suppressed dimension-five interactions arising from gravitational effects. We perform a general analysis of gravitationally induced $R_P$ violation and identify two plausible and astrophysically consistent scenarios for achieving the required suppression.

hep-ph↗

arXiv1996

Searching for Relic Neutralinos using Neutrino Telescopes

Neutrino telescopes of large area offer the possibility of searching for indirect signals of relic neutralinos in the galactic halo, due to annihilations in the Sun or the Earth. Here we investigate the sensitivity, using a supergravity scheme where the soft scalar mass terms are not constrained by universality conditions at the grand unification scale. We first discuss in which regions of the supersymmetric parameter space the neutralino may be considered as a good candidate for cold dark matter. The discovery potential of the search using neutrino telescopes is then compared to that of the direct search for relic neutralinos.

hep-ph↗

arXiv1996

Non--Baryonic Dark Matter

The best particle candidates for non--baryonic cold dark matter are reviewed, namely, neutralino, axion, axino and Majoron. These particles are considered in the context of cosmological models with the restrictions given by the observed mass spectrum of large scale structures, data on clusters of galaxies, age of the Universe etc.

astro-ph↗

arXiv1995

Last Hope for an astrophysical solution to the solar neutrino problem

We discuss what appears the last hope for an astrophysical solution to the solar neutrino problem: a correlated variation of the astrophysical factors for the helium burning cross sections ($S_{33}$ and $S_{34}$) and either $S_{17}$ or the central temperature $T_c$. In this context, we recognize the important role played by the CNO neutrinos. In fact, we can obtain a fair fit to the experimental data only if three conditions are met simultaneously: the astrophysical factor $S_{33}$ is about 200 times what is presently estimated, the astrophysical factor $S_{17}$ is about 3 times larger and the $^{13}$N and $^{15}$O neutrino fluxes are negligible compared to the ones predicted by standard solar models. These conditions are not supported by the present data and their correlated combination is improbable.

astro-ph↗

arXiv1995

Neutralino dark matter in supersymmetric models with non--universal scalar mass terms

Neutralino dark matter is studied in the context of a supergravity scheme where the scalar mass terms are not constrained by universality conditions at the grand unification scale. We analyse in detail the consequences of the relaxation of this universality assumption on the supersymmetric parameter space, on the neutralino relic abundance and on the event rate for the direct detection of relic neutralinos.

hep-ph↗

arXiv1995

Curvature Radiation by Ultrarelativistic Protons

We study pion curvature radiation by a proton, i.e. pion emission by a proton moving along a curved trajectory. We suggest an approximate semiclassical solution and the exact solution for which we assume that a proton moves in a fictitious magnetic field with the Larmor radius equal to the curvature radius of the real trajectory. As possible application we consider the pion radiation by ultrahigh energy protons moving along curved magnetic field lines. Such situation can occur in the magnetosphere of a young pulsar, in the magnetosphere of the accretion disk around a black hole, and in the vicinity of a superconducting cosmic string. The decay products of these pions, such as high energy photons or neutrinos, can give the observable consequences of the considered mechanism.

hep-ph↗

arXiv1994

The MSW solution to the solar neutrino problem for non-standard solar models

The difficulties for non-standard solar models (NSSM) in resolving the solar neutrino problem are discussed stressing the incompatibility of the gallium--Kamiokande data, and of the gallium--chlorine data. We conclude that NSSM's cannot explain simultaneously the results of any two of the solar neutrino data (chlorine, Kamiokande and gallium). We address further the question whether the MSW solution exists for NSSM's (e.g. models with $^8$B neutrino flux much lower than the standard one and/or central temperature $T_c$ very different from $T_c^{\text{SSM}}$). We demonstrate that the MSW solution exists and is very stable relative to changes of $S_{17}$ ($S$-factor for $p$ + $^7$Be reaction) and $T_c$. In particular, $Δm^2$ is almost constant while $\sin^2 2θ$ depends on the exact values of $S_{17}$ (or $^8$B-neutrino flux) and $T_c$.

hep-ph↗

arXiv1994

High Energy Gamma--Radiation from the Galactic Center due to Neutralino Annihilation

We study the NGS (Non--dissipative Gravitational Singularity) model, which successfully describes the non--linear stage of evolution of perturbations (see [1], [2] and references therein). This model predicts DM density distribution $ρ(r) \sim r^{-α}$ with $α\simeq 1.8$ which holds from very small distances $r_{\rm min} \simeq 0.01~{\rm pc}$ up to very large distances $r_{\rm max} \simeq 5~{\rm Mpc}$. Assuming the neutralino to be a CDM particle, we calculate the annihilation of neutralinos in the vicinity of the singularity (Galactic Center). If neutralinos are the dominant component of DM in our Galaxy, the produced energy is enough to provide the whole observed activity of the GC. Neutralinos of the most general composition and of mass in the range $20~{\rm GeV} \leq m_\c \leq 1~{\rm TeV}$ are considered. We find the neutralino compositions which give the relic density needed for the Mixed Dark Matter (MDM) model and we evaluate for these compositions the high--energy ($E_γ > 100 ~{\rm MeV}$) gamma--ray flux under the constraint that the radio flux is lower than the observational limit. The compositions with the detectable gamma--ray flux which we found are provided by a set of almost pure gaugino states with the neutralino mass between $100$ and $500$ GeV. We demonstrate that a detectable high--energy gamma--ray flux is produced by the neutralino annihilation also in the case when neutralinos provide a small fraction (down to $0.1 \%$) of the DM in our Galaxy. The predicted flux is $F_γ\sim 10^{-7}-10^{-8}~{\rm cm}^{-2}~{\rm s}^{-1}$ for $E_γ\gsim 300~{\rm MeV}$

hep-ph↗

arXiv1993

The KeV Majoron as Dark Matter Particle

We consider a very weakly interacting KeV majoron as dark matter particle (DMP), which provides both the critical density $ρ_{cr} = 1.88 \times 10^{-29} h^{2}$ $g/cm^{3}$ and the galactic scale $M_{gal}$ $\sim m^{3}_{Pl}/m^{2}_{J} \sim 10^{12} M_{\odot} (m_{J}/1 KeV)^{-2}$ for galaxy formation. The majoron couples to leptons only through some new "directly interacting particles", called DIPS, and this provides the required smallness of the coupling constants. If the masses of these DIPS are greater than the scale $V_s$ characterizing the spontaneous violation of the global lepton symmetry they are absent at the corresponding phase transition ($T \sim V_s$) and the majorons are produced during the phase transition, never being in thermal equilibrium during the history of the universe. In the alternative case $m_{DIP} < V_{s}$ the majorons can be for a short period in thermal equilibrium. This scenario is not forbidden by nucleosynthesis and gives a reasonable growth factor for the density fluctuations compatible with COBE. A possible signature is an X-ray line at $E_γ= \frac{m_J}{2}$, produced by the decay $J \to γ+ γ$. A model is described which realizes the possibility of the KeV majoron as DMP and may also lead to observable rates for decays such as $μ\ra e γ$ and $μ\ra 3e$.

hep-ph↗