Charge Ratio Of Cosmic Ray Muons Research Articles

Measurement of the cosmic ray muon charge ratio with the OPERA detector

The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the cosmic ray muon charge ratio Rμ=Nμ+/Nμ− in the TeV energy region. Rμ is shown as a function of the “vertical surface energy” Eμcosθ. A fit to a simplified model of muon production in atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.

The OPERA experiment at Gran Sasso

OPERA (Oscillation Project with Emulsion tRacking Apparatus) is a long baseline neutrino experiment aiming to detect for the first time the appearance of tau neutrinos in a pure muon neutrino beam. The OPERA detector is exposed to the CNGS beam (CERN Neutrinos to Gran Sasso), a high-intensity and high-energy beam of muon neutrinos produced at the CERN SPS and directed toward the Gran Sasso underground laboratory (LNGS), 730 km away. The LNGS laboratory is situated under an average depth of 3800 meters water equivalent, making OPERA the deepest experiment able to measure cosmic ray muons with a magnetized detector, e.g. the cosmic ray muon charge ratio. Cosmic ray events were observed, together with the first neutrino beam events, during the 2007 and 2008 CNGS runs. This paper reviews the experimental apparatus, presents the first results for neutrino data and describes the analysis of cosmic ray data.

A compact detector for the measurement of the cosmic-ray muon charge ratio

A compact sampling calorimeter is developed and used to measure the ratio between positive and negative muons in the cosmic-ray flux at momenta below 1 GeV/ c. The delayed coincidence method is used, based on the reduced mean lifetime of negative muons due to nuclear capture in matter. It is shown that aluminum is a good choice as a capture medium for negative muons and suitable for a simple detector set-up. The muon charge ratio is found to be 1.30±0.05 for a mean momentum of 0.86 GeV/ c and over a zenith angle acceptance with Θ mean=26°.

New interpretation of the charge ratio of Cosmic-Ray muons

The charge ratio of cosmic-ray muons at sea-level is calculated by using recent experimental results on cosmic-ray primaries and hadron (lepton)-nucleus collisions. It is shown that the charge ratio agrees with the observed ratio up to 10 TeV if a fraction 0.05 of quark-gluon plasma state in nucleus-nucleus collisions is included.

Scaling parameters in inclusive reactions p+p→c+X at ISR energies and the charge ratio of cosmic-ray muons

Scaling parameters in inclusive reactions p+p→c+X at ISR energies and the charge ratio of cosmic-ray muons

Dependence of the cosmic ray muon charge ratio at sea level on kaons produced as a consequence of neutron interactions

An important refinement to a calculation of the dependence of the muon charge ratio on muon energy is reported. The refinement is concerned with the manner in which kaons produced in neutron-nucleon interactions in the atmosphere are considered in the model. The predicted variation of the muon charge ratio is in good agreement with the experimental observations, although the predicted absolute magnitude of the ratio is approximately 7.5% too high.

Charge ratio of energetic cosmic-ray muons as a function of zenith angle

A summary has been made of all the available data on the charge ratio of cosmic-ray muons at energies above 50 GeV. The data have been combined into zenith-angle bins and average values have been plotted for mean angles of approximately 0°, 60° and 80°. Following the method outlined by MacKeown and Wolfendale an approximate analysis has been made to determine limits on the ratio of kaons to pions (K/π) and K+/K− for energetic secondaries produced in the interactions of primary particles in the energy range (500÷10000) GeV. It is shown that there is no evidence for a dramatic change in these quantities over the next decade of energy above that available at the Intersecting Storage Ring experiment at CERN.

Muon Charge-Ratio Measurement and Comparison with Prediction from Hadronic Scaling

The cosmic-ray muon charge ratio has been measured for muon momenta 0.7-4.5 TeV/c. It has also been calculated for a constant primary composition by applying scaling to nuclear-target data. The measurements, together with those at lower energies, are in good agreement with our predictions for primary collision energies up to 40 TeV.

Measurement of Cosmic-Ray Muon Charge Ratio at Sea Level Between Energies of 10 and 1500 GeV

Measurement of Cosmic-Ray Muon Charge Ratio at Sea Level Between Energies of 10 and 1500 GeV

The muon spectra near the geomagnetic equator

The vertical momentum spectrum and the charge ratio of cosmic-ray muons have been investigated in the range 0.3–25 GeV/c at a geomagnetic latitude of λ = 9 °N at sea level. The investigations have been performed by means of a magnetic spectrograph using the spark chamber technique for track location. The measured spectrum in the low-energy region is about 20% smaller than the spectra at high geomagnetic latitudes. The integral intensity for particles which penetrate more than 15 cm of lead is 7.25 × 10−3 cm−2 s−1 sr−1. The theoretical spectrum after Olbert is in agreement with our results.

The interpretation of the charge ratio of cosmic-ray muons

From a survey of all the available experimental data on the charge ratio of muons in the cosmic radiation a best estimate of its energy dependence is presented, both in the vertical direction and at large zenith angles. A discussion is given of the relevant parameters for its interpretation and the predictions of various models of particle production are investigated. It is found that pionization alone is unable to explain the data, even allowing for fluctuations in inelasticity and multiplicity to the extent observed in other high-energy experiments. The parameters of models involving kaon and pion production needed to explain the ratio are determined. At present, explanation in terms of kaon production is slightly more probable.

Measurements of the charge ratio of cosmic-ray muons

Results are presented of two independent determinations of the charge ratio of cosmic-ray muons, at energies up to several hundred GeV. In one case the data are based on 19 235 particles collected in a smaller angular range about the vertical, and in the other case measurements refer to the range of zenith angles 77.5°-90° and comprise 10 832 particles. The various factors relevant to a transformation of the observed charge ratio to that at production are considered, after which a comparison is made both between the two series and with the result of other authors.

On the charge ratio of cosmic-ray muons at sea level

An attempt is made to explain the charge (+/-) ratio of cosmic-ray muons at energies ≿ 40 GeV observed at sea level on the basis of the production of pions in the normally considered inelastic interactions of nucleons as also through the decay of isobars produced in thequasi-elastic scattering of high-energy nucleons.