The spatial distribution of cascade particles in extensive air showers from cosmic rays with energies of
E
0
≥ 10
17
eV is studied at the Yakutsk array using surface scintillation detectors in ...continuous observations from 1977 to 2017. The experimental data are compared to calculations obtained with different models of hadron interactions. The mass composition of the cosmic rays changes from 〈ln
A
〉 ∼ 2.5 to the mass composition of protons in the energy range of (1–20) × 10
17
eV.
An experimental setup is being developed to extract Ba ions from a high-pressure Xe gas environment. It aims to transport Ba ions from 10bar Xe to vacuum conditions. The setup utilizes a ...converging–diverging nozzle in combination with a radio-frequency (RF) funnel to move Ba ions into vacuum through the pressure drop of several orders of magnitude. This technique is intended for use in a future multi-ton detector investigating double-beta decay in 136Xe. Efficient extraction and detection of Ba ions, the decay product of 136Xe, would allow for a background-free measurement of the 136Xe double-beta decay.
The lateral distribution of muons with threshold
E
μ
≈ 1.0secθ GeV in extensive air showers with energies
E
0
≥ 10
17
eV for the observation period of 2011–2013 is investigated. The observations show ...that in the energy range of 1–5 ×10
17
eV, the depth of the maximum
X
m
on the cascade curve grows relatively quickly, due to the composition of cosmic rays changing from predominantly iron nuclei to protons at
E
0
≈ 10
17
eV.
We present new data on Cherenkov light observations obtained during 1994-2009 period, after a modernization of the Yakutsk EAS array. A complex analysis of xmax and its fluctuations σ(xmax ) was ...performed in a wide energy range. With the new data, according to QGSJet II model, an estimation was made of cosmic rays mass composition for E0 ~1017 -3×1019 eV. The result points towards a mixed composition with a large portion of heavy nuclei at E0 ~1017 eV and the dominance of light nuclei at E0 ~1019 eV. The analysis of σxmax energy dependence for the same energies qualitatively confirms this result. A shape of xmax distribution at fixed energy 1018 eV is analysed to make more precise conclusion on cosmic ray mass composition.
We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for an exposure of 32.5 kg yr, with a background of ∼1.5×10(-3) kg(-1) yr(-1) keV(-1) in the ...±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay T(1/2)(0νββ)(136Xe)>1.6×10(25) yr (90% C.L.), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.
Here we consider the results of direct measurements of muons in extensive air showers with zenith angles \(\theta \le 45^{\circ}\) and energy above \(10^{17}\) eV, obtained at the Pierre Auger ...Observatory and Yakutsk array. In both experiments muons were registered with underground scintillation detectors with \(\approx 1.0 \times \sec\theta\) GeV energy threshold. Measured density values were compared to theoretical predictions calculated within the framework of the QGSJet-II.04 hadron interaction model. They differ by factor \(1.53 \pm 0.13\)(stat). We demonstrate that this difference is due to overestimation of muon densities by 1.22 times and underestimation of primary energy by 1.25 times in the Auger experiment.
The composition of the primary cosmic radiation should be studied by various alternative approaches. A promising way is to exploit a dependence of the fraction of muons in an extensive air shower on ...the atomic number of the primary nuclei. A comparison of the fraction of muons at 600 m from the shower axis observed at the Yakutsk array in the vertical air showers at ultra-high energies with results of simulations in terms of QGSJET-II and Gheisha-2002d models carried out with the help of the CORSIKA 6.616 and GEANT4 codes showed rather heavy composition of the primary radiation. But some errors in these models should be taken into account. At last, one has to allow for the fact that signals in the surface and underground scintillation detectors of the Yakutsk array from various particles of extensive air showers are measured in different units. All these corrections taken together show the proton composition of the primary radiation in the energy region of ~2.·1018 – 1019 eV. At lower energies a composition is heavier. The change from the heavy composition to the primary protons occurs in the energy interval of 9.·1017 – 2.·1018 eV. It is not excluded that at energies above 1.1·1019 eV the composition may be also heavier as illustrated by a trend of data.
Lateral distribution of muons in extensive air showers registered at the Yakutsk array was investigated. The analysis covers two periods of observation: before 2018 and after 2020, when the revision ...of muon detectors with 1-GeV threshold was complete. Measured values of muon density are compared to computational results obtained within the framework of two hadron interaction models. Within the energy domain above \(10^{18}\) eV the best agreement is observed for proton composition primary cosmic rays.
Results obtained from an analysis of the energy spectrum of cosmic rays with energies in the region of \(E_0 \ge 10^{17}\) 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 the QGSJET01, QGSJET-II-04, SIBYLL-2.1, and EPOS-LHC models by employing the CORSIKA code package. The new estimate of \(E_0\) is substantially lower than its counterpart used earlier.
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