Search

BM@N (Baryonic Matter at Nuclotron) is the first experiment operating and taking data at the Nuclotron/NICA ion-accelerating complex.The aim of the BM@N experiment is to study interactions of relativistic heavy-ion beams with fixed targets. We present a technical description of the BM@N spectrometer including all its subsystems., Comment: 34 pages, 47 figures, 6 tables

First physics results of the BM@N experiment at the Nuclotron/NICA complex are presented on {\pi}+ and K+ meson production in interactions of an argon beam with fixed targets of C, Al, Cu, Sn and Pb at 3.2 AGeV. Transverse momentum distributions, rapidity spectra and multiplicities of $\pi^+$ and $K^+$ mesons are measured. The results are compared with predictions of theoretical models and with other measurements at lower energies., Comment: 29 pages, 20 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.

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

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 early Universe scenario which allows for production of non-Gaussian curvature perturbations at small scales. We study the peculiarities of a formation of primordial black holes (PBHs) connected with the non-Gaussianity. In particular, we show that PBH constraints on the values of curvature perturbation power spectrum amplitude are strongly dependent on the shape of perturbations and can significantly (by two orders of magnitude) deviate from the usual Gaussian limit ${\cal P}_\zeta \lesssim 10^{-2}$. We give examples of PBH mass spectra calculations and PBH constraints for the particular case of the curvaton model., Comment: The manuscript has some intersections with arxiv:1210.3262 but contains new ingredients and more precise conclusions; title is changed appropriately. Includes 13 pages, 4 figures. Accepted for publication in Int. J. Mod. Phys. 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., Comment: v2: 11 pages, 5 figures. Extended version accepted by Phys. Rev. D

We consider several early Universe models that allow for production of large curvature perturbations at small scales. As is well known, such perturbations can lead to formation of primordial black holes (PBHs). We briefly review the today's situation with PBH constraints and then focus on two models in which strongly non-Gaussian curvature perturbations are predicted: the hybrid inflation waterfall model and the curvaton model. We show that PBH constraints on the values of curvature perturbation power spectrum amplitude are strongly dependent on the shape of perturbations and can significantly (by two orders of magnitude) deviate from the usual Gaussian limit ${\cal P}_\zeta \lesssim 10^{-2}$. We give examples of PBH mass spectra calculations for both inflationary models., Comment: 14 pages, 8 figures. v2: References added, some misprints are corrected. arXiv admin note: substantial text overlap with arXiv:1112.5601

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

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

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

The today's energy density of the induced (second order) gravitational wave background in the frequency region $\sim 10^{-3} - 10^3$ Hz is constrained using the existing limits on primordial black hole production in the early Universe. It is shown, in particular, that at frequencies near $\sim 40$ Hz (which is the region explored by LIGO detector), the value of the induced part of $\Omega_{GW}$ cannot exceed $(1-3)\times 10^{-7}$. The spread of values of the bound is caused by the uncertainty in parameters of the gravitational collapse of black holes., Comment: 5 pages, 1 figure; v2: revised version of the manuscript, accepted for publication in JETP Letters

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., Comment: v2: 14 pages, 7 figures; revised version of the manuscript, accepted for publication in Phys. Rev. D

Experimental data of arrays "Andyrchy" and "Carpet-2" of Baksan Neutrino Observatory (Institute for Nuclear Research), obtained in the regime of a detection of the single cosmic-ray component, are used for a search of the bursts of cosmic gamma rays from evaporating primordial black holes. Different theoretical models of the evaporation process are used for the analysis. Distributions of the counting rate fluctuations on both arrays agree with the expectations from the cosmic ray background. The new constraints on the concentration of evaporating primordial black holes in the local region of Galaxy are obtained. The comparison of the results of different experiments is given., Comment: 5 pages, 3 figures. Extended variant of the talk prepared for the 31st International Cosmic Ray Conference, to be held in Lodz, Poland, 2009

The technical procedure of a search of bursts of very high energy gamma rays from evaporation of primordial black holes on air-shower array "Andyrchy" of Baksan Neutrino Observatory of Institute for Nuclear Research is described. The theoretical model used in the present work assumes that the chromosphere around the evaporating black hole does not form. For minimization of the cosmic ray background the method of multidimensional analysis of modelled as well as experimentally detected events is applied. The new upper limit on the concentration of evaporating primordial black holes in the local region of Galaxy is obtained. The comparison of the results of different experiments is given., Comment: 4 pages, 6 figures. A talk prepared for the 31st International Cosmic Ray Conference, to be held in Lodz, Poland, 2009

We calculate differential energy spectra ($x_F$-distributions) of charmed particles produced in proton-nucleus collisions, assuming the existence of intrinsic heavy quark components in the proton wave function. For the calculation, the recently proposed factorization scheme is used, based on the Color Glass Condensate theory and specially suited for predictions of a production of particles with large rapidities. It is argued that the intrinsic charm component can, if it exists, dominate in a sum of two components, intrinsic + extrinsic, of the inclusive spectrum of charmed particles produced in proton-nucleus collisions at high energies, in the region of medium $x_F$, $0.15 < x_F < 0.7$, and can give noticeable contribution to atmospheric fluxes of prompt muons and neutrinos., Comment: 10 pages, 4 figures. Version published in J. Phys. G.

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 with large (~ 0.01 - 0.1) values at some scale of comoving wave numbers k. In the calculation we take into account the explicit dependence of gravitational (Bardeen) potential on time. Using the PBH mass spectra, we further calculate the neutrino and photon energy spectra in extragalactic space from evaporation of light PBHs, and the energy density fraction contained in PBHs today (for heavier PBHs). We obtain the constraints on the model parameters using available experimental data (including data on neutrino and photon cosmic backgrounds). We briefly discuss the possibility that the observed 511 keV line from the Galactic center is produced by annihilation of positrons evaporated by PBHs., Comment: 15 pages, 11 figures. v2: version prepared for the publication in the journal. The introduction is rewritten, many new references are added. v3: published version. Several clarifications were added, title was changed according to the Editor's recommendation

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

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., Comment: 4 pages, 2 figures

Possibilities of an experimental search for gamma-ray bursts from primordial black hole (PBH) evaporations in space are reconsidered. It is argued that the corresponding constraints which can be obtained in experiments with cosmic ray detectors strongly depend on theoretical approach used for a description of the PBH evaporation process. Predictions of several theoretical models for gamma-ray spectra from final stages of PBH life (integrated over time) are given., Comment: Contribution to the 30th International Cosmic Ray Conference, Merida, Mexico, July 2007; 4 pages, 5 figures

We calculate neutrino and photon energy spectra in extragalactic space from evaporation of primordial black holes, assuming that the power spectrum of primordial density fluctuations has a strong bump in the region of small scales. The constraints on the parameters of this bump based on neutrino and photon cosmic background data are obtained., Comment: 6 pages, 4 figures

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., Comment: Talk given at the NANP'05 conference, June 2005. 5 pages, one eps figure

Diffuse background of high energy neutrinos arising from interactions of cosmic ray protons with far infrared radiation background in extragalactic space is calculated. It is assumed that cosmic ray spectrum at superhigh energies has extragalactic origin and is proton dominated.The cosmological evolution of extragalactic sources of cosmic ray protons as well as infrared-luminous galaxies is taken into account in the calculation., Comment: 4 pages, 4 figures, to be published in Proceedings of the 29th ICRC, Pune, India, 3-10 August, 2005