TUNKA-133: A new array for the study of ultra-high energy cosmic rays

A new array for studying ultra-high energy cosmic rays was inaugurated in 2009 in the Tunka Valley, about 50 km from Lake Baikal. Having an area of 1 km², the new facility allows us to study cosmic rays with energies of 10¹⁵–10¹⁸ eV via the a unified method for registering Cherenkov radiation from extensive air showers (EASes) and is making a substantial contribution to understanding the origin of ultra-high energy cosmic rays. We describe the current state of the experiment, the new methodological approach, our initial results, and the plans for further development of the array.     

Ultra-high energy cosmic rays threshold in Randers-Finsler space

Kinematics in Finsler space is used to study the propagation of ultra high energy cosmic rays particles through the cosmic microwave background radiation. We find that the GZK threshold is lifted dramatically in Randers-Finsler space. A tiny deformation of spacetime from Minkowskian to Finslerian allows more ultra-high energy cosmic rays particles to arrive at the earth. It is suggested that the lower bound of particle mass is related with the negative second invariant speed in Randers-Finsler space.     

Ultra-high energy cosmic rays threshold in Randers-Finsler space

Kinematics in Finsler space is used to study the propagation of ultra high energy cosmic rays particles through the cosmic microwave background radiation. We find that the GZK threshold is lifted dramatically in Randers-Finsler space. A tiny deformation of spacetime from Minkowskian to Finslerian allows more ultra-high energy cosmic rays particles to arrive at the earth. It is suggested that the lower bound of particle mass is related with the negative second invariant speed in Randers-Finsler space.     

Modeling Source Spectra and Composition of Ultrahigh Energy Cosmic Rays

The inverse problem of cosmic ray transport of ultra-high energy cosmic rays is considered. The source spectrum and composition are derived based on the recent Auger data on energy spectrum, energy dependence of mean logarithm of atomic mass number and its variance. The dependence of results on the extrapolation of observable spectrum beyond energies 10²⁰ eV is investigated.

     

Neutrino—nucleon cross-section at ultra-high energies in models with large extra dimensions

We examine whether the models with large extra dimensions can provide an explanation for the GZK violating ultra-high energy cosmic rays (UHECR). In these models the neutrino—nucleon cross-section rises rapidly with energy and hence cosmic rays might be identified with neutrinos. We calculate the neutrino-nucleon cross-section at ultra high energies by assuming that it is dominated by the production ofp-branes. We perform the calculation in a generalized Randall-Sundrum model and Lykken-Randall model and find cross-sections of the order of 100 mb at neutrino energies of 10²⁰ eV, which is required for explaining UHECR events.     

Main results of the study of ultrahigh-energy cosmic rays in the Yakutsk Extensive Air Shower Array

This paper describes the current state of the Yakutsk Extensive Air Shower Array (EASA) and the prospects for its modernization. The main results of the study of the energy spectrum, mass composition, and anisotropy of the ultra-high energy cosmic rays (UHECRs) that were obtained recently by the array are given.     

Muons of very and ultra-high energy cosmic rays

In many cosmic rays experiments at very and ultra-high energies, an excess of muons (including those of very high energy, >100 TeV) is observed that cannot be explained within existing models of hadron interactions. This excess is usually explained in terms of the heavier mass composition of primary cosmic rays. However, the excess over the predicted values even for extremely heavy compositions, and especially the observed excesses of muons with energies of >100 TeV, requires that we consider other possibilities with respect to the generation of muons, including changes in models of hadron interaction.     

Portion of muons with a threshold energy above 1 GeV in extensive air showers with ultra-high energies,according to the Yakutsk EAS array data

Characteristics of the muon component in extensive air showers and the fluctuations of muons are considered. In this work, we compare experimental data with computations performed for various models of the hadron interactions of protons and iron nuclei. The aim of this analysis is to obtain information on the mass composition of cosmic rays in an ultra-high energy region.     

Composition of Cosmic Rays with Energy More than 0.1 EeV by Long-Term Optical Observations of Cherenkov Emission at Yakutsk EAS Array

Physics of Atomic Nuclei - The paper presents results on longitudinal development of air showers with ultra-high energies and mass composition of cosmic rays 〈ln A〉. The data is...     

Estimation of The Cosmic Ray Mass Composition at Energy Above 10 17 eV According to Scintillation Detectors of the Yakutsk Array

The lateral distribution of cascade particles was studied in extensive air showers initiated by cosmic rays with energies above 1017 eV. The study is based on experimental data of ground-based and ground-shielded (with ∼1-GeV energy threshold) scintillation detectors of the Yakutsk EAS array collected during the continuous observational period from 1977 to 2017. Particle density measured in experiment is compared to the results of simulations performed with the use of several ultra-high energy hadron interaction models. The best agreement between theory and experiment was obtained for qgsjet01 and qgsjet ii-04 models. Interpretation of our data has indicated that within the energy range (1–30) × 1017 eV the cosmic ray mass composition changes from nuclei of intermediate group towards protons.     

Bursts of gravitational radiation from superconducting cosmic strings and the neutrino mass spectrum

Berezinsky, Hnatyk and Vilenkin showed that superconducting cosmic strings could be central engines for cosmological gamma-ray bursts and for producing the neutrino component of ultra-high energy cosmic rays. A consequence of this mechanism would be that a detectable cusp-triggered gravitational wave burst should be released simultaneously with the γ-ray surge. If contemporary measurements of both γ and ν radiation could be made for any particular source, then the cosmological time-delay between them might be useful for putting unprecedentedly tight bounds on the neutrino mass spectrum. Such measurements could consistently verify or rule out the model, since strictly correlated behaviour is expected for the duration of the event and for the time variability of the spectra.     

超高能宇宙线的研究

本文分四个部分讨论了超高能宇宙线的现象:(1)超高能宇宙线的一些特性:原初宇宙线的能谱和成份。(2)超高能宇宙线与核的相互作用。(3)广延大气簇射的一些实验结果。(4)稀有现象。文章还评述了超高能宇宙线的几点倾向性结论。     

Cascade Particles in Extensive Air Showers with Energy Above 10 17 eV According to Longstanding Measurements at the Yakutsk Array

Lateral distribution of cascade particles was studied in extensive air showers initiated by cosmic rays with energy above 1017 eV. The study is based on the data collected with ground-based scintillation detectors of the Yakutsk array during the continuous observational period from 1977 to 2017. Particle density measured in experiment is compared to the results of simulations performed for primary protons and iron nuclei within the framework of four ultra-high energy hadronic interaction models. Particle density obtained in the simulation was converted to signal of the scintillation detectors of the array. From the parameters of the resulted lateral distribution function, features of extensive air showers longitudinal development were derived.     

Muons in Extensive Air Showers with Energy above 10 17 eV According to the Long Standing Studies at the Yakutsk Array

lateral distribution of muons was studied in extensive air showers initiated by cosmic rays with energy above 1017 eV. The study is based on the experimental data of underground scintillation detectors with 1-GeV energy threshold collected during the continuous observational period lasting from 1986 to 2017. Experimentally measured values of muon density are compared to results of simulations performed for primary protons and iron nuclei within the framework of four ultra-high energy hadronic interaction models. The density of particles with 1-GeV threshold obtained in simulations was then converted to the signal of ground-shielded scintillation detectors of the array. Studying the features of the resulting muon lateral distribution has allowed us to reconstruct parameters of longitudinal development of extensive air showers.     

Ultrahigh energy cosmic rays,cosmological constant,and theta vacua

We propose that the origin of ultrahigh energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff and the origin of small cosmological constant can both be explained by vacuum tunneling effects in a theory with degenerate vacua and fermionic doublets. By considering the possibility of tunneling from a particular winding number state, accompanied by violation of some global quantum number of fermions, the small value of the vacuum dark energy and the production of high energy cosmic rays are shown to be related. We predict that the energy of such cosmic rays should be at least 5x10(14) GeV.     

Spectrum of ultrahigh-energy cosmic rays

Detailed calculation of the energy spectra of ultrahigh-energy cosmic rays has been performed. The spectral features related to the interaction of protons with cosmic microwave background have been analyzed. The calculated spectra are compared with the experimental data obtained at the giant detectors for ultrahigh-energy cosmic rays.     

Violation of the Greisen-Zatsepin-Kuzmin cutoff: a tempest in a (magnetic) Teapot? Why cosmic ray energies above 10(20) eV may not require new physics

The apparent lack of suitable astrophysical sources for the observed highest energy cosmic rays within approximately 20 Mpc is the "Greisen-Zatsepin-Kuzmin (GZK) paradox." We constrain representative models of the extragalactic magnetic field structure by Faraday rotation measurements; limits are at the microG level rather than the nG level usually assumed. In such fields, even the highest energy cosmic rays experience large deflections. This allows nearby active galactic nuclei (possibly quiet today) or gamma ray bursts to be the source of ultrahigh energy cosmic rays without contradicting the GZK distance limit.     

Nonextensive thermal sources of cosmic rays

The energy spectrum of cosmic rays exhibits power-like behavior with a very characteristic ‘knee’ structure. We consider a possibility that such a spectrum could be generated by some specific nonstatistical temperature fluctuations in the source of cosmic rays with the ‘knee’ structure reflecting an abrupt change of the pattern of such fluctuations. This would result in a generalized nonextensive statistical model for the production of cosmic rays. The possible physical mechanisms leading to these effects are discussed together with the resulting chemical composition of the cosmic rays, which follows the experimentally observed abundance of nuclei.     

Spectra of Protons and Alpha Particles and Their Comparison in the NUCLEON Experiment Data

JETP Letters - The aim of the NUCLEON space experiment was to measure spectra of high-energy cosmic rays. Direct measurements of energy spectra of protons and nuclei of cosmic rays which allow...     

Extremely high energy cosmic rays

The evidence for the existence of cosmic rays with energies in excess of 10²⁰ eV is now overwhelming. There is so far no indication of the GZK cutoff in the energy spectrum at 5 × 10¹⁹ eV. This conclusion is not firm for lack of statistics. A cutoff would be expected if the sources of the cosmic rays were distributed uniformly throughout the cosmos. The sources of cosmic rays with energy above the GZK cutoff must be at a distance ≤ 100 Mpc, and if they are protons they are very likely to point to these sources. There are no easy explanations how known astrophysical objects can accelerate protons (or atomic nuclei) to these energies. This difficulty has led to speculation that there may be exotic sources such as topological defects which produce these energetic cosmic rays directly along with a copious supply of neutrinos of similar energy. The fluxes of these cosmic rays is very low and large instruments are required to observe them even with modest statistics. One such instrument, the Pierre Auger Observatory, is described. It is designed for all-sky coverage and the construction of its southern site will begin in Argentina in 1999.