Interactions Of Cosmic Ray Muons Research Articles

The rise of muon content in extensive air showers after the 3 PeV knee of the primary cosmic ray spectrum according to data of the Tien Shan mountain installation

We put together the experimental results on muon component of extensive air showers (EAS) which were gained with various techniques at the detector complex of the Tien Shan mountain station. According to this comparison, the problem of the EAS muon content in the range of primary cosmic ray energies (1–100)PeV seems to be more complicated than it was usually supposed. Generally, from the models of nuclear interaction it follows that the EAS which have produced gamma-hadron families in the Tien Shan X-ray emulsion chamber did preferably originate from interaction of the light cosmic ray nuclei, such that their muon abundance must be ∼1.5 times below an average calculated over all showers. In contrary, the experimental muon counts in the EAS with families demonstrate a (1.5–2)-fold excess above the average, and this difference starts to be observable in the showers with the energy above the 3PeV knee of the primary cosmic ray spectrum. Later on, the rise of muon production in EAS after the knee was confirmed at Tien Shan by another experiment on detection of the neutrons stemmed from interaction of cosmic ray muons. Thus, the results obtained by the two completely different methods do mutually agree with each other but contradict to the common models of hadron interaction.

Underground neutron events at Tien Shan

The events of multiple neutron production under a 2000 g/cm2 thick rock absorber were studied at the Tien Shan mountain cosmic ray station, at an altitude of 3340 m above the sea level. From comparison of the experimental and Geant4 simulated neutron multiplicity spectra it follows that the great bulk of these events can be explained by interaction of cosmic ray muons with internal material of neutron detector. In synchronous operation of the underground neutron monitor with the Tien Shan shower detector system it was found that the characteristics of the muonic component of extensive air showers which is seemingly responsible for generation of neutron events underground do change noticeably within the energy range of the knee of primary cosmic ray spectrum. Some peculiar shower events were detected when the neutron signal reveals itself only ∼100–1000 µs after the passage of the front of shower particles which probably means an existence of corresponding delay of the muon flux in such events.

Interaction of cosmic ray muons with spent nuclear fuel dry casks and determination of lower detection limit

The potential non-proliferation monitoring of spent nuclear fuel sealed in dry casks interacting continuously with the naturally generated cosmic ray muons is investigated. Treatments on the muon RMS scattering angle by Moliere, Rossi-Greisen, Highland and, Lynch-Dahl were analyzed and compared with simplified Monte Carlo simulations. The Lynch-Dahl expression has the lowest error and appears to be appropriate when performing conceptual calculations for high-Z, thick targets such as dry casks. The GEANT4 Monte Carlo code was used to simulate dry casks with various fuel loadings and scattering variance estimates for each case were obtained. The scattering variance estimation was shown to be unbiased and using Chebyshev's inequality, it was found that 106 muons will provide estimates of the scattering variances that are within 1% of the true value at a 99% confidence level. These estimates were used as reference values to calculate scattering distributions and evaluate the asymptotic behavior for small variations on fuel loading. It is shown that the scattering distributions between a fully loaded dry cask and one with a fuel assembly missing initially overlap significantly but their distance eventually increases with increasing number of muons. One missing fuel assembly can be distinguished from a fully loaded cask with a small overlapping between the distributions which is the case of 100,000 muons. This indicates that the removal of a standard fuel assembly can be identified using muons providing that enough muons are collected. A Bayesian algorithm was developed to classify dry casks and provide a decision rule that minimizes the risk of making an incorrect decision. The algorithm performance was evaluated and the lower detection limit was determined.

Neutron Production by Cosmic Ray Muons at the Sudbury Neutrino Observatory

Neutrons produced by cosmic ray muon interactions can be a significant background in sensitive underground experiments. The Sudbury Neutrino Observatory (SNO) is an efficient and well-calibrated neutron detector capable of measuring the rate and characteristics of neutrons produced by muon interactions in its heavy water target, light water shielding and surrounding rock. The location of the detector, beneath a rock overburden of 2092 m (5890 ± 94 m water equivalent), means that the muon flux is particularly low in rate and high in energy. SNOʼs measurements, with unique target materials and high energy muons, are important for benchmarking Monte Carlo simulations. These simulations will be used to predict the muon-induced neutron fluxes in future low background experiments.

Uranium groundwater anomalies at LNGS: From the neutron flux background to the geodynamic processes

Monitoring of chemical and physical groundwater parameters has been carried out worldwide in seismogenic areas with the aim to test possible correlations between their spatial and temporal variations and strain processes. It is shown in this paper that uranium groundwater anomalies, which were observed in cataclastic rocks crossing the underground Gran Sasso National Laboratory (LNGS), can be used as a possible strain meter in domains where continental lithosphere is subducted. Moreover, whereas at the Gran Sasso National Laboratory only the natural radioactivity in the rock, the concrete, as well as the induced part coming from interaction of cosmic ray muons with the rock or the detector materials itself were considered as possible sources for the neutron flux background, the water-rock interaction and its spatial-temporal variation induced by the hydrological pattern of the Gran Sasso aquifer must be taken into account. Water must be considered not only as moderator in concrete, but also as additional source for neutron flux modulation due to its variable concentration and its radioactivity.

Coincidence Techniques in Gamma-ray Spectroscopy

Abstract In many different gamma-ray detection systems, the events are registered in coincidence, i.e. within short time interval, by two or more detectors. Depending on purpose of an experiment, these events can be rejected (anticoincidence counting) or acquired (coincidence counting). The construction, setup and application of several coincidence systems in Laboratory for nuclear physics of Department of Physics in Novi sad are presented. The anti-Compton shield for HPGe detector based on big annular NaI(Tl) detector and corresponding measurement which proved existing of 283 keV level in Ba-137 populating by beta decay of Cs-137, is described. The application of this system (in addition with NaI(Tl) plug detector) where HPGe detector is actively shielded by NaI(Tl) detector for investigation of double beta decay of positron emitters (Cr-50, Zn-64,) is also shown. The improving of detection limit of HPGe detector by the active shield consisting of five plastic scintillation detectors is presented, as well as the measurements of cross sections for X-ray production, induced by interaction of cosmic-ray muons with massive lead shield. We found that the prompt and delayed coincidence events between plastic veto detector and Ge detector can be sharply divided in two groups. Also, the bremsstrahlung and annihilation events can be time resolved from (n,n’) events, although all these events belong to the group of delayed events.

Rate of germanium-isotope production by background processes in the SAGE experiment

Data on a direct determination of systematic uncertainties caused by the background production of germanium isotopes in the radiochemical SAGE experiment measuring the solar-neutrino flux are analyzed. The result obtained for the rate of 68Ge production is 6.5(1±1.0) times greater than the expected one; the rate of 69Ge production does not exceed preliminary estimates. The above result for 68Ge corresponds to the systematic uncertainty that is caused by the interaction of cosmic-ray muons and which is equal to 5.8% (4.5 SNU) at a solar-neutrino-capture rate of 77.0 SNU. An experiment is proposed that would test the effect of cosmic-ray muon influence on the SAGE systematic uncertainty and which would be performed at the location of the underground scintillation telescope facilities of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences).

Muon-induced neutron and pion production in an organic liquid scintillator at a shallow depth.

The production of fast neutrons and pions by inelastic interactions of cosmic-ray muons in an organic liquid scintillator has been investigated. A detector filled with 190 liters of a 0.09% gadolinium-loaded liquid scintillator was installed in the Stanford Underground Facility, at an underground depth of approximately 20 meters water equivalent. The detector served as the target material for hadron production. Our measurements find a single-neutron production yield of (4.3\ifmmode\pm\else\textpm\fi{}0.3\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ neutrons per muon g/${\mathrm{cm}}^{2}$ and a double-neutron production yield of (1.6\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\pm\else\textpm\fi{}0.5)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ double neutrons per muon g/${\mathrm{cm}}^{2}$. We measured a ${\mathrm{\ensuremath{\pi}}}^{+}$ production yield of (3.5\ifmmode\pm\else\textpm\fi{}0.2\ifmmode\pm\else\textpm\fi{}0.7)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ pions per muon g/${\mathrm{cm}}^{2}$. Nearly all the ${\mathrm{\ensuremath{\pi}}}^{+}$ produced were accompanied by neutrons. These yields were dependent on the energy threshold of the muon trigger, revealing an enhancement associated with hadronic showers initiated by muons. The production yield due to nonshowering muons was lower: 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}5}$ neutrons per muon g/${\mathrm{cm}}^{2}$, with a single-to-double neutron multiplicity ratio of roughly 4:1. The nonshowering muon ${\mathrm{\ensuremath{\pi}}}^{+}$ production probability was 2.5\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}6}$ pions per muon g/${\mathrm{cm}}^{2}$, with about half of these nonshowering ${\mathrm{\ensuremath{\pi}}}^{+}$ events accompanied by neutrons.

Observation of electromagnetic interactions of high energy muons deep underground.

The first experimental measurement of the spectrum of cascade showers produced by cosmic ray muon interactions deep underground in the transferred energy range 0.4--200 GeV has been performed by means of the NUSEX calorimeter at a depth of about 5000 hg/${\mathrm{cm}}^{2}$, the average muon energy being close to 360 GeV. The spectrum of energy transfers is in good agreement with calculations based on the commonly used theoretical formulas for muon interaction cross sections and on a conservative picture of the formation of muon energy spectrum at great depths. The present data do not confirm the deficit of the cross section at low energy transfers for the 1 TeV muon energy recently reported by the CCFR Collaboration. A possible explanation of the difference between the observed and the expected stochastic energy loss distributions presented by the CCFR group is discussed.

Neutron background for a dark matter experiment at a shallow depth site

The neutron flux in the Stanford Underground Facility, a shallow depth site with an overburden of 17 ± 1 m.w.e., has been measured using a moderated BF 3 proportional counter. This counter has also been used to measure the neutron flux inside various shielding configurations required for a dark matter search at this site. These measurements demonstrate that lead shielding, used for photon attenuation, acts as a strong neutron source, with the neutrons being produced primarily by cosmic ray muon interactions within the lead. We have determined the production rate of cosmic ray induced neutrons in lead at this depth. Fortunately, these measurements also demonstrate that it is possible to moderate and capture these neutrons so that the resulting neutron flux is no longer sensitive to the presence of the lead shielding. For a dark matter search, however, care still has to be taken to minimize the inactive mass near the detector.

Inelastic scattering of cosmic ray muons on iron nuclei and the virtual photon shadowing

Hadronic cascade showers originating from inelastic interactions of cosmic ray muons with iron nuclei have been observed in a calorimeter located between two magnetic spectrometers. The separation of those events from the electromagnetic showers has been successfully done in the ranges of the transferred energy v ≳ 50 GeV and its ratio to muon energy v/E ≳ 0,1, by utilizing the difference of their longitudinal cascade developments. The comparison of the obtained μ-Fe cross section with available μ-, e- and σ-proton data as well as μ-, e- and σ-nucleus data indicates that; 1 At v ˜ 100 GeV, the virtual photon cross section on iron nucleus is almost the same as the real photon one, at least Q2 ≳ 0.1 GeV2/c2, and is about 70% of the cross section on proton times the atomic mass number of iron, i.e. the shadowing effect is clearly seen. 2 Up to TeV region, this virtual photon cross section on iron does not increase significantly. contrary to the tendency of the real photon cross section on proton around 100 GeV. This suggests most likely that the shadowing still increases with energy at such high energies.

A calorimeter to study cosmic ray muon interactions

A calorimeter with a volume of 3.6×4×2.4 m 3 has been built in the Institute for Cosmic Ray Research, University of Tokyo to study the interactions of cosmic ray muons of known momenta. The calorimeter is located between the two magnets of MUTRON, a magnet spectrometer built by the same laboratory to measure muon momenta up to a maximum of 17 TeV c −1. In this article, the design of the calorimeter is described and the characteristics of the counters used are reported. The expected number of the interactions and the accuracy of energy determinations by the calorimeter are also discussed.

The electromagnetic interactions of cosmic ray muons in iron

A study of the electromagnetic interactions of muons of energy 7-700 GeV in a thick iron absorber has been made with the Durham spectrograph, MARS. Whilst it is never possible in such an interaction experiment to study one of the interaction processes alone, by classifying the experimental data into various ranges of muon energy and energy transfer it is shown that one of the interaction processes can be made to dominate. The measured interaction probabilities agree within the limits of experimental error with those calculated theoretically for energy transfers of 1-100 GeV from muons of energy 7-700 GeV.

A search for a charge dependence of the interaction cross sections of cosmic ray muons

Using the Durham spectrograph, MARS, a search for a charge asymmetry of the interactions of cosmic ray muons has been made. There is no evidence from the experiment in support of a charge asymmetry; the ratio of the interaction probability for positive muons to that of a negative muons is 1.020+or-0.031 for interactions in which two or more secondaries are recorded.

Study of the charge asymmetry in electromagnetic interactions of cosmic ray muons

The Durgapur cosmic ray spectrograph has been utilised to study the electromagnetic interaction of cosmic ray muons in iron in the momentum range 5–100 GeV/ c. The dependence of the interaction cross section on the charge of the muons for the production of a single electron secondary due to the knock-on process and for two and more two electrons due to both knock-on and pair production has been investigated. The ratio of the interaction cross section for positive muons to that for negative muons in the magnetic-iron has been found to be 0.952 ± 0.045 for the production of one secondary particle. For production of two and more than two secondaries the ratios are 1.05 ± 0.09 and 0.91 ± 0.08 respectively. The present results do not indicate any charge asymmetry of cosmic ray muons in respect of electromagnetic interactions in iron.

Electromagnetic interactions of cosmic ray muons in iron. I. Search for a charge asymmetry

A search for a charge asymmetry in the interactions of cosmic ray muons in iron has been made using the Durham spectrograph MARS. The measurements cover the range of muon energy 6-200 GeV and refer to interaction secondaries varying in number from one to about 20. The ratio of the interaction probability for positive muons to that for negative muons is 1.08+or-0.06 for interactions having two or more secondaries. This value is less than that found in some previous experiments and does not give support to the existence of a charge asymmetry.

Electromagnetic interactions of cosmic ray muons in iron. II. Momentum dependence of the interaction probabilities

For pt.i see Ibid., vol.5, no.12, 1706. The Durham spectrograph MARS has been used to study the electromagnetic interactions of cosmic ray muons in iron in the energy range 6-200 GeV. The interaction probabilities for producing single electrons and electron bursts of various sizes from the knock-on process, direct electron pair production and bremsstrahlung are investigated as a function of muon energy. Reasonable agreement between the measured probabilities and those predicted has been found and it is concluded that significant deviations from accepted theory are not likely.

Electromagnetic interactions of cosmic-ray muons at large zenith angles at sea level

The electromagnetic interactions of cosmic-ray muons incident at sea level in the zenith angle range 50-90 degrees have been studied. The measurements cover energy transfers from 3 to 240 GeV produced by muons in the energy range 34 to 520 GeV. No significant divergence from accepted theory has been found.

Electromagnetic Interactions of High-Energy Cosmic-Ray Muons

The electromagnetic interactions of cosmic-ray muons in the energy range up to 1 TeV were investigated with a spark-chamber calorimeter in combination with the Kiel spectrograph. The purpose was to investigate the different kinds of electromagnetic processes (knock-on, direct-pair, bremsstrahlung, and multiple pion production) in the range of energy transfer from 0.2 to 100 GeV. The production of pions is in reasonable agreement with the theoretical prediction of Daiyasu et al. In the region of high energy transfer (>2 Gev) the experimental results agree with Bhabha's theory of the knock-on process as well as with Murota's theory of direct pair production. However, in the region of energy transfer around 1 GeV there are minor deviations from these theories, in contradiction with accelerator data.

Some Implications of a New Source of Cosmic-Ray Muons

We study implications of the recent experiment by the University of Utah cosmic-ray group, which presents evidence for a new source of cosmic-ray muons. The data imply the existence of a new class of hadrons $X$, produced in pairs with a cross section \ensuremath{\gtrsim}0.3 mb in primary cosmic-ray collisions of energy g${10}^{12}$-${10}^{13}$ eV. The $X$, although stable under strong and electromagnetic interactions, decays with large branching ratio into states containing a muon and with lifetime ${10}^{\ensuremath{-}7}$-${10}^{\ensuremath{-}8}$ sec. The total mass of the produced $X$ pair is estimated to be less than 55 GeV. We examine the possible quantum numbers of $X$. We study possible new interactions of cosmic-ray muons and neutrinos underground. In particular, the muon electromagnetic field should photoproduce $X$; the cross section for this process is estimated to be \ensuremath{\sim}${10}^{\ensuremath{-}32}$ ${\mathrm{cm}}^{2}$ and may lead to observation of pairs of muons under ground with small lateral separation or measurable angular divergence. The hypothesis $X=W=\mathrm{intermediate}$ boson for the weak interactions is considered; the experimental limits on the production of $W$ by neutrinos and muons underground, along the with absence of large $\ensuremath{\nu}\ensuremath{-}p$ elastic scattering at accelerator energies, place strong, and possibly fatal, constraints on this interpretation. The importance of the polarization of the muon beam underground in these considerations is pointed out. Finally, further experimental consequences of the existence of $X$ are discussed.