Searching for Neutrino and Ultra-High-Energy Gamma-Ray Counterparts of the GCN Alerts

Physics of Atomic Nuclei - The Baksan Neutrino Observatory setups are currently performing search for neutrino and ultra-high-energy gamma-ray counterparts of the events on the Gamma-ray...     

Status of the Yakutsk Air Shower Array and Future Plans

Physics of Atomic Nuclei - The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world’s largest...     

Ultra-High Energy Cosmic Ray Study Results by Radio Emission Technique at Yakutsk Array

Physics of Atomic Nuclei - The Yakutsk array is designed to study cosmic rays at energy 1015–1020 eV. The array detects charged particles, muons, Cherenkov light and radio emission....     

Ultra-High Energy Gamma Ray Astronomy with the Carpet Air Shower Array at the Baksan Neutrino Observatory

Journal of Experimental and Theoretical Physics - The Carpet facility of the Baksan Neutrino Observatory (Institute for Nuclear Research of the Russian Academy of Sciences) was put into operation...     

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.     

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.     

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.     

Neutrino physics at the turn of the millennium

I discuss the implications of the latest data on solar and atmospheric neutrinos which strongly indicate the need for physics beyond the Standard Model. I review the theoretical options for reconciling these data in terms of three-neutrino oscillations. Even though not implied by the data, bimaximal models of neutrino mixing emerge as an attractive possibility. Supersymmetry with broken R-parity provides a predictive way to incorporate it, opening the possibility of testing neutrino anomalies at high-energy collider experiments such as the LHC or at the upcoming long-baseline or neutrino factory experiments. Reconciling, in addition, the hint provided by the LSND experiment requires a fourth, light sterile, neutrino. The simplest theoretical scenarios are the most symmetric ones, in which two of the four neutrinos are maximally mixed and lie at the LSND scale, while the others are at the solar mass scale. The lightness of the sterile neutrino, the nearly maximal atmospheric neutrino mixing, and the generation of Δm _⊙ ² &; Δm _atm ² all follow naturally from the assumed lepton-number symmetry and its breaking. These two basic schemes can be distinguished at neutral-current-sensitive solar &; atmospheric neutrino experiments such as the Sudbury Neutrino Observatory. However, underground experiments have not yet proven neutrino masses, since there is a variety of alternative mechanisms. For example, flavor changing interactions can play an important role in the explanation of solar and of contained atmospheric data and could be tested through effects such as μ → e+γ, μ-e conversion in nuclei, unaccompanied by neutrino-less double beta decay. Conversely, the room is still open for heavy unstable neutrinos. A short-lived ν_μ might play a role in the explanation of the atmospheric data. Finally, in the presence of a sterile neutrino v_s, a long-lived ν_τ in the MeV range could delay the time at which the matter and radiation contributions to the energy density of the Universe become equal, reducing the density fluctuations on the smaller scales and rescuing the standard cold-dark-matter scenario for structure formation. In this case, the light v_e ν_μ, and v_s would account for the solar and atmospheric data.     

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...     

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from the Ground-Based Scintillation Detectors of the Yakutsk EAS Array

Journal of Experimental and Theoretical Physics - The energy spectrum of cosmic rays with energies E0 ≥ 1017 eV over the period of continuous observations in 1974–2017 is analyzed. A...     

Neutrino geophysics and astronomy at Baksan Neutrino Observatory: Potential of the spectroscopy of natural antineutrino sources

Prospects for studying, at the Baksan Neutrino Observatory, geoneutrinos, as well as neutrinos from supernovae, by means of a scintillation spectrometer having a target mass of 5000 t are considered. It is shown that the geographical location, a deep position (4800 mwe), and a modest background of antineutrinos from nuclear reactors makes the Baksan Neutrino Observatory one of the best places for performing such investigations. Particular attention is given to the derivation of information about the nature of neutrinos, the possibility of detecting relic neutrinos from supernovae, and the discovery of a hypothetical georeactor.     

Estimate of the Integral Photon Flux in the Region of Extremely High Energies in Complex Yakutsk EAS Array Data

A complex analysis of Yakutsk EAS array data has been performed in order to search for primary photons generating extensive air showers with energies above 10¹⁸ eV. Analyzing calculations and experimental data, selection criteria have been formulated and used to make a sample of showers close in their characteristics to showers initiated by primary photons. An upper limit of the integral photon flux in cosmic rays of extremely high energies has been estimated from these data.     

Energy Spectrum of Ultrahigh-Energy Cosmic Rays according to Data from Ground-Based Scintillation Detectors of the Yakutsk EAS Array

Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of E₀ ≥ 10¹⁷ eV over the period of continuous observations from 1974 to 2017 are presented. A refined expression for estimating the primary-particle energy is used for individual events. This expression is derived from calculations aimed at determining the responses of the ground-based and underground scintillation detectors of the Yakutsk array for studying extensive air showers (EAS) and performed within theQGSJET-01-d, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHCmodels by employing the CORSIKA code package. The new estimate of E₀ is substantially lower than its counterpart used earlier.     

Neutrino production of same-sign dimuons at the Fermilab Tevatron

The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of μ^?μ^? events and 25 μ⁺μ⁺ events withP _μ>9 GeV/c, produced in 1.5 millionv _μ and 0.3 million \(\overline {v_\mu }\) induced charged-current events with energies between 30 GeV and 600 GeV. The data were obtained with the Chicago-Columbia-Fermilab-Rochester (CCFR) neutrino detector in the Fermilab Tevatron Quadrupole Triplet Neutrino Beam during experiments E 744 and E 770. After background subtraction, the prompt rate of same-sign dimuon production is (0.53±0.24)×10^?4 perv _μ charged-current event and (0.52±0.33)×10^?4 per \(\overline {v_\mu }\) charged-current event. The kinematic distributions of the same-sign dimuon events after background subtraction are consistent with those of the non-prompt background due to meson decays in the hadron shower of a charged-current event. Calculations ofc \(\bar c\) gluon bremsstrahlung, based on improved measurements of the charm mass parameter and nucleon structure functions by the CCFR collaboration, yield a prompt rate of (0.09±0.39)×10^?4 perv _μ charged-current event. In this case,c \(\bar c\) gluon bremsstrahlung is probably not an observable source of prompt same-sign dimuons.     

A new method for observing the shower cascade profile at the Yakutsk EAS array

An empirical approach is presented for reconstruction of the extensive air shower (EAS) cascade curve according to data of the Cherenkov track detector. The proposed method, unlike conventional ones, is based on experimentally measured parameters and on calculated values which weakly depend on the model of shower development.     

Early Attempts to Detect the Neutrino at the Cavendish Laboratory

In the 1920s and early 1930s the Cavendish Laboratory in Cambridge was preeminent in experimental research on radioactivity and nuclear physics, with theoretical physics playing a subsidiary role in guiding, but not determining the course of experimental research. Soon after Wolfgang Pauli (1900–1958) proposed his neutrino hypothesis in 1930 to preserve conservation of energy and momentum in beta decay, experiments – the first of their kind – were carried out in the Cavendish Laboratory to detect Pauli’s elusive particle, but they were abandoned in 1936. I trace these early attempts and suggest reasons for their abandonment, which may contribute to an understanding of the complex way in which theoretical entities are accepted by physicists.     

Neutrino flavor ratio on Earth and at astrophysical sources

We present the reconstruction of neutrino flavor ratios at astrophysical sources. For distinguishing the pion source and the muon-damped source to the 3 σ level, the neutrino flux ratios, R≡?(ν_μ)/(?(ν_e)+?(ν_τ)) and S≡?(ν_e)/(?(ν_τ)), need to be measured in accuracies better than 10%.     

Neutrino emissivity of quark matter at finite temperatures

We evaluate the emissivity rates for d-decay and s-decay by exactly solving the angular integrals involved and without assuming the degeneracy of electrons. We have also studied the effects of QCD coupling constant as well as the s-quark mass on the emissivity rates. We find that these parameters are important in determining the threshold and extinction densities for d- and s-decays.