E. V. Bugaev

The Baikal underwater neutrino telescope: Design, performance and first results

Abstract A first deep underwater detector for muons and neutrinos, NT-200 , is currently under construction in Lake Baikal. Part of the detector, NT-36 , with 36 photomultiplier tubes at three strings, has been installed in 1993. This array allowed for the first time a three-dimensional mapping of Cherenkov light deep underwater. Since then, various arrays have been almost continuously taking data. Presently a 96-PMT array is operating. We describe the NT-200 detector design and present results obtained with NT-36 .

Atmospheric muon flux at sea level, underground, and underwater

The vertical sea-level muon spectrum at energies above 1 GeV and the muon intensities at depths up to 18 km w.e. in different rocks and in water are calculated. The results are particularly collated with a great body of the ground-level, underground, and underwater muon data. In the hadron-cascade calculations, we take into account the logarithmic growth with energy of inelastic cross sections and pion, kaon, and nucleon generation in pion-nucleus collisions. For evaluating the prompt-muon contribution to the muon flux, we apply the two phenomenological approaches to the charm production problem: the recombination quark-parton model and the quark-gluon string model. To solve the muon transport equation at large depths of a homogeneous medium, we used a semianalytical method, which allows the inclusion of an arbitrary ~decreasing! muon spectrum at the medium boundary and real energy dependence of both continuous and discrete muon energy losses. The method is checked for accuracy by direct Monte Carlo calculation. Whenever possible, we give simple fitting formulas describing our numerical results. @S0556-2821~98!00313-0# PACS number~s!: 13.85.Tp, 96.40.Tv

Formation of primordial black holes from non-Gaussian perturbations produced in a waterfall transition

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

MUM: flexible precise Monte Carlo algorithm for muon propagation through thick layers of matter

\beta_{PBH}

Constraints on amplitudes of curvature perturbations from primordial black holes

.

Axion inflation with gauge field production and primordial black holes

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.

Constraints on the induced gravitational wave background from primordial black holes

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

Curvature perturbation spectra from waterfall transition, black hole constraints and non-Gaussianity

{\mathcal{P}}_{\mathcal{R}}(k)

Constraints on diffuse neutrino background from primordial black holes

with large (

Induced gravitational wave background and primordial black holes

\ensuremath{\sim}{10}^{\ensuremath{-}2}\char21{}{10}^{\ensuremath{-}1}