The energy spectrum of neutrons produced by cosmic ray muons in LVD

The energy spectrum of neutrons produced by cosmic ray muons in the underground detector LVD (3650 m.w.e.) is obtained for the energy range of 30–450 MeV. The spectrum is derived using the energy release spectrum of neutron interaction products in 1.5 m³ scintillation counters.     

Analysis of seasonal variations of the cosmic ray muon flux and neutrons produced by muons in the LVD detector

The Russian-Italian Large Volume Detector (LVD) is located at the Gran Sasso underground laboratory at a depth of 3300 m w.e. To study the seasonal variations of the penetrating component of cosmic rays, the data on cosmic ray muons detected in 2001–2008 was analyzed, along with those associated with neutrons produced by muons since April 2003. One-year periodic variations of muons and neutrons produced by them were found. The maximum intensity is observed in July, in accord with theoretical concepts.     

Neutrons produced by muons in the LVD matter

The calculation results on the production, transport, and capture of neutrons produced by muons passing through the LVD are presented. The calculations are performed using the Monte Carlo transport codes GEANT4 and SHIELD. The efficiency of detecting the neutrons produced in both the scintillator and the detector’s structure is determined.     

Status of the LVD experiment

The large-volume detector operating at the Gran Sasso National Laboratory, Italy, is intended primarily for detecting neutrinos from gravitational collapses in the Galaxy. The apparatus consisting of scintillation detectors, with a total scintillator mass of ～1 kt, interleaved with iron (～1 kt) has been collecting data since 1992. No candidates for neutrino bursts from collapsing stars have been found. The new upper limit of the frequency of supernova bursts in the Galaxy is reported. The results of the investigation of the space distribution of muon-produced neutrons are presented, and the possibilities for determining the charge composition of muon fluxes with energies E _μ > 5 TeV are considered.     

Role of very-high-energy muons in generation of penetrating cascades in the Pamir experiment

The question of processes responsible for some unusual events with the energy deposition over 100 TeV recorded in X-ray emulsion chambers (XECs) of the Pamir experiment is still open. Among the events of this type are penetrating cascades in deep lead XECs. The evaluations show that these events can be qualitatively explained by multiple interactions of muons with energies in the PeV range. In this work, the expected number of penetrating cascades induced in the Pamir XECs by very-high-energy muons is calculated for different muon generation processes in the atmosphere.     

Variations of neutrons and muons generated by cosmic rays in the atmosphere and in thunderstorm electric fields

We investigate the interrelation between cosmic rays (CRs) and the electric field of the Earth during thunderstorms established by various investigators. The data from simultaneous measurements by spectrograph of CRs and the electric field in Yakutsk are used. It is noted that in seven recorded events of prolonged (up to 9 hours) variations in the electric field by ±5 kV m⁻¹ and in one event of a one-hour increase in the field value up to +20 kV m⁻¹ the CR index rose substantially. During the thunderstorm of the latter event, the intensity of neutrons fell by a considerable 1%. At the same time, a drop of ∼0.3% was observed in the CR muon component. Such effects was not observed for higher energy muons.     

The multiple scattering of cosmic-ray muons in magnetic spectrometers

Summary The multiple scattering of high-energy cosmic-ray muons in solid-iron magnetic-momentum spectrometers is investigated theoretically and the results are compared with experimental measurements. In particular, spectrometers which record orthogonal views of the muon trajectory are considered. In spectrometers of this type typically two projected angles are measured: 1) an angle ϕ_T in a plane perpendicular to the magnetic field and 2) another angle, ϕ _y , in a plane containing the magnetic-field vector. In the present work a new parameter α=ϕ _y /σϕT is defined and the theory of Molière is used to derive a multiple-scattering probability distribution,f(α), which can be directly compared to spectrometer data. Here σ is the constant noise-to-signal ratio of the spectrometer as calculated by the Molière theory. The new multiple-scattering distributionf(α) is independent of the cosmic-ray spectrum, thus allowing for the first time cosmic-ray spectrometer data to be used directly to investigate the predictions of multiple-scattering theory. Good agreement between theory and experiment is demonstrated for a sample of 8000 muon events measured with the AMH magnetic spectrometer.

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Riassunto Si studia dal punto di vista teorico lo scattering multiplo di muoni dei raggi cosmici ad alta energia negli spettrometri ad impulso magnetico di ferro solido e i risultati sono confrontati con le misurazioni sperimentali. In particolare, si considerano spettrometri che registrano vitse ortogonali della traiettoria del muone. In spettrometri di questo tipo si misurano tipicamente due angoli proiettati: 1) un angolo ϕ_T in un piano perpendicolare al campo magnetico e 2) un altro angolo, ϕ _y , in un piano contenente il vettore del campo magnetico. In questo lavoro, si definisce un nuovo parametro α=ϕ _y /σϕ_T e la teoria di Molière è usata per derivare una distribuzione di probabilità per lo scattering multiplo,f(α), che può essere direttamente confrontata con i dati dello spettrometro. Qui σ è il rapporto costante rumore-segnale dello spettrometro come calcolato con la teoria di Molière. La nuova distribuzione dello scattering multiplof(α) è indipendente dallo spettro dei raggi cosmici, permettendo così di usare per la prima volta direttamente i dati dello spettrometro dei raggi cosmici per studiare le predizioni della teoria dello scattering multiplo. Si mette in evidenza un buon accordo tra dati teorici e sperimentali per un campione di 8000 eventi muonici misurati con uno spettrometro magnetico AMH.

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Резюме Теоретически исследуется многократное рассеяние космических мюонов высоких энергий в магнитных импульсных спектрометрах. Полученные результаты сравниваются с экспериментом. В частности, рассматриваются спектрометры, которые регистрируют мюонную траекторию с взаимноперпендикулярных точек зрения. В спектрометрах этого типа измеряются два угла: 1) угол ϕ_T в плоскости, перпендикулярной магнитному полю и 2) другой угол ϕ _y в плоскости, содержащей вектор магнитного поля. В настоящей работе определяется новый параметр α=ϕ _y /σϕ_T и используется теория Мольера для вывода распределения вероятности многократного рассеяния,f(α), которое можно непосредственно сравнить со спектрометрическими данными. В этой работе с представляет постоянное отношение шума к сигналу для спектрометра, вычисленное с помощью теории Мольера. Новое распределение многократного рассеянияf(α) не зависит от спектра космических лучей. Таким образом, впервые данные спектрометра для космических лучей непосредственно исполязуются для исследования предсказаний теории многократного рассеяния. Обнаружено хорошее согласие между теорией и экспериментом на примере 8000 мюонных событий, измеренных с помощью АМН магнитного спектрометра.

     

On possible role of neutrons in appearance of delayed muons in MUON-T setup at the Tien Shan high-altitude station

The MUON-T setup operated at the Tien Shan high-altitude station of the Lebedev Physical Institute (3340 m above sea level) at a soil depth of ∼10 m (∼20 m m.w.e.). Muons with delay times of 30–150 ns with respect to the extensive air shower front were observed at this setup. Calculations showed that delay times of relativistic muons, taking into account their deviations in the geomagnetic field, do not exceed ∼30 ns. To elucidate the possible role of neutrons in the appearance of delayed events due to the n-p reaction in the plastic scintillator material, the problem of neutron transport in a medium with a density of 2 g/cm³ and a humidity of 10% was solved by the Monte Carlo method. Calculations for a point source of neutrons with energies of 5, 10, and 20 MeV (such neutrons can be generated, in particular, in cascades in soil from hadrons of the shower core) showed that the neutron flux decreases more than by a factor of 10⁴ at a distance of 2.8 m of soil from the source. Neither neutron crosses the boundary of 3m at the total statistics of 3 · 10⁵ events. Since the MUON-T setup is at a depth of 10 m, it is clear that neutrons from the atmosphere and soil upper layer are absorbed, scattered, and do not reach the detector. Thus, the formation of delayed muons in the MUON-T setup cannot be explained by these neutrons.     

Solar diurnal anisotropy measured using muons in GRAPES-3 experiment in 2006

The GRAPES-3 experiment at Ooty contains a large-area (560 m²) tracking muon detector. This detector consists of 16 modules, each 35 m² in area, that are grouped into four supermodules of 140 m² each. The threshold energy of muons is sec(θ) GeV along a direction with zenith angle θ and the angular resolution of the muon detector is 6°. Typically, it records ~4×10⁹ muons every day. The muon detector has been operating uninterruptedly since 2001, thus providing a high statistics record of the cosmic ray flux as a function of time over one decade. However, prior to using these data, the muon rate has to be corrected for two important atmospheric effects, namely, variations in atmospheric pressure and temperature. Because of the near equatorial location of Ooty (11.4°N), the seasonal variations in the atmospheric temperature are relatively small and shall be ignored here. Due to proximity to the equator, the pressure changes at Ooty display a dominant 12 h periodic behaviour in addition to other seasonal changes. Here, we discuss various aspects of a novel method for accurate pressure measurement and subsequent corrections applied to the GRAPES-3 muon data to correct these pressure-induced variations. The pressure-corrected muon data are used to measure the profile of the solar diurnal anisotropy during 2006. The data, when divided into four segments, display significant variation both in the amplitude (~45%) and phase (~42 m) of the solar diurnal anisotropy during 2006, which was a period of relatively low solar activity.     

High-energy multiple muons viewed from the observation of gamma-ray families at mountain altitudes

Summary Based on the knowledge of the nature of primary cosmic rays inferred from the observations of gamma-ray family events with the largescale emulsion chamber experiments at Mt. Fuji and at Mt. Kanbala, the three-dimensional Monte Carlo simulation on the high-energy multiple-muon events has been carried out. By comparing the simulation results with the presently available observed ones, it is concluded that the hypothesis for the composition of primary cosmic rays being heavy-nuclei dominant, given from the analysis of gamma-ray family events, is quite consistent with the observed results on the lateral spread of multiple-muon events.

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Riassunto Si effettua la simulazione di Monte Carlo tridimensionale sugli eventi di muoni multipli ad alta energia, basandosi sulla conoscenza della natura dei raggi cosmici primari inferita dalle osservazioni degli eventi della famiglia di raggi gamma con gli esperimenti su larga scala della camera ad emulsione sul Monte Fuji e sul Monte Kanbala. Confrontando i risultati della simulazione con quelli osservati attualmente disponibili, si conclude che l'ipotesi della composizione dei raggi cosmici primari in cui predominano i nuclei pesanti, data dall'analisi degli eventi della famiglia di raggi gamma, risulta del tutto coerente con i risultati osservati sulla diffusione laterale degli eventi a muoni multipli.

     

Relevance of multiple muons detected underground to the mass composition of primary cosmic rays

Summary Calculations have been made of the expected frequencies of multiple muons for the situation of the Soudan underground proton decay detector. Comparisons are made with the observations and it is concluded that with our model for high-energy collisions the flux of heavy nuclei (A>20, principally iron) in the range (10¹⁵÷10¹⁶ eV)/nucleus is at most 25% of the total particle flux in the same range.

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Riassunto Sono stati effettuati i calcoli delle frequenze attese di muoni multipli per situare il rivelatore di decadimento di protoni sotterraneo di Soudan. Si eseguono confronti con le osservazioni e si conclude che con il nostro modello per le collisioni ad alta energia il flusso di nuclei pesanti (A>20, specialmente ferro) nell'intervallo (10¹⁵÷10¹⁶) eV/nucleo è al massimo il 25% del flusso totale di particelle nello stesso intervallo.

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Резюме Вычисляются ожидаемые частоты появления множественных мюонов в суданском подземном детекторе распадов протонов. Проводится сравнение с результатами наблюдений. Делается вывод, что в рамках предложенной модели для соударений при высоких энергиях поток тяжелых ядер (A>20, в основном, ядра железа) в области энерий (10¹⁵÷10¹⁶) эВ составляет, в лучшем случае, 25% от полного потока частиц в этой области энергий.

     

Monte Carlo simulation of quasi-elastic scattering and above-barrier neutrons in the neutron lifetime experiment MAMBO I

Motivated by the strong disagreement of a recent result for the neutron lifetime with the previous world average value we report results of a Monte Carlo simulation of the neutron lifetime experiment MAMBO I, which was carried out some 20 years ago. In addition to all experimental parameters and procedures known to us, the analysis included quasi-elastic neutron scattering on the surface of liquid fomblin oil wall coatings of the UCN storage vessel, and above-barrier neutrons. The original analysis, leading to the published result of 887.6 ± 3 s, did not take into account these effects. For an exemplary set of model parameters we find a negative correction of 6.0 seconds, which demonstrates that these hitherto neglected effects may be very important also in the analysis of other neutron lifetime experiments using UCN storage vessels with fomblin oil coating close to room temperature.     

Verification of the weak equivalence principle with Laue diffracting neutrons: Test experiment

We propose a novel experiment to test the weak equivalence principle (WEP) for the Laue diffracting neutron. Our experiment is based on an essential magnification of an external affect on neutron diffracting by Laue for the Bragg angles close to the right one in couple with additional enhancement factor which exists due to the delay of the Laue diffracting neutron at such Bragg angles. This enhancement phenomena is proposed to be utilized for measuring the force which deviates from zero if WEP is violated. The accuracy of measuring inertial to gravitational neutron masses ratio for the introduced setup can reach ～10^?5, which is more than one order superior to the best present-day result.     

On the capture of muons in atoms

In previous calculations on the capture of negative muons in atoms we used the average energy loss per unit path length as a frictional force in the classical equations of motion. In the present note it is shown that the rare events where the muon, because of its high velocity in the inner parts of the atom, loses an energy which is larger than its total energy, are important for the average stopping power. For the calculation of capture ratios these large energy losses should be treated separately. The results differ significantly from those obtained previously, and are in better agreement with experiment.     

High-energy hadrons and cosmic-ray muons in the atmosphere

Summary The experimental data on fluxes of high-energy hadrons and muons in the atmosphere are compared with the predictions based on the latest information about the properties of high-energy interactions and the primary cosmic-ray composition. It is demonstrated that the expected fluxes are in good agreement with the observations if protons dominate at energies up to 10¹⁵ eV.

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Riassunto Si confrontano i dati sperimentali sui flussi degli adroni e muoni ad alta energia nell'atmosfera con de previsioni basate sulle informazioni piú recenti sulle proprietà delle interazioni ad alta energia e la composizione primaria dei raggi cosmici. Si dimostra che i flussi attesi sono in buon accordo con le osservazioni se i protoni dominano ad energie fino a 10¹⁵ eV.

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Резюме Экспериментальные данные для потоков высокоэнергетических адронов и мюонов сравниваются с предсказаниями, основанными на последней информации относительно свойств взаимодействий при высоких энергиях и составе первичных космических лучей. Показывается, что ожидаемые потоки хорошо согласуются с наблюдениями, если протоны доминируют при энергиях вплоть до 10¹⁵ эВ.

     

Single domain generation in YBCO textured samples

This paper discusses the partial melting technique applied to texture cylindrical YBa₂Cu₃O_6+x samples with Y₂BaCuO₅ additions and the experimental procedures developed for obtaining large single domains. The thermal texturing methods produce liquid migration which hinders the stable and continuous solidification process. In the present work different methodologies for avoiding capillary liquid absorption are discussed. The mechanism of single domain selection is studied and an interpretation proposed explaining the oblique angle that the (001) plane of the single domain forms with the sample axis. This mechanism is also compatible with the shape of the recrystallization front shown by the samples studied. In order to impose axial orientation of the (001) crystallographic planes, solidification experiments with textured YBCO seeds are carried out.     

Temperature variations in the flux of high-energy muons

The flux of high-energy muons (threshold energy, 220 GeV) as a function of atmospheric temperature is measured using data from the Baksan Underground Scintillation Telescope (BUST). The temperature was measured every 12 h by radiosonde at different levels of observations. The results from studying the correlation coefficient between the counting rate of muons and the temperature of the atmosphere at different altitudes are presented.     

Multiple scattering of muons in beryllium

The defocussing and the depolarization of a high energy muon beam in a beryllium filter, often used to eliminate accompanying pions, have been studied. The quantum mechanical transport equation of Waldmann, which can also be used to describe the multiple scattering of Dirac particles, is solved with a distorted wave Born approximation. Calculations are done for both the Thomas-Fermi and the Hartree-Fock potential of the beryllium atom. It is shown that the Hartree-Fock potential leads to a less divergent beam. The depolarization of a longitudinally polarized muon beam in passage through a thin beryllium foil is also studied.