Cosmic-ray Muon Spectrum Research Articles

The momentum spectrum of muons at sea level in the range 5-1200 GeV/c

The momentum spectrum of sea level cosmic ray muons has been measured for near vertical incidence in the range 5 GeV/c<p<1200 GeV/c by the Durgapur cosmic ray spectrograph. The measured spectrum compares well with that predicted from the pion diffusion model based on the assumption of 100% pions as the parent of muons. The exponent of the pion production spectrum has been determined to be -2.61-0.02+0.03. The present results are compared with the results of other workers.

Energy spectrum and angular distribution of cosmic ray muons in the range 50-70 GeV

The energy dependence and angular distribution of the sea level muon intensity have been determined from measurements made inside the second pyramid at Giza, Cairo. It is concluded from these measurements that the sea level muon integral spectrum may be represented in the energy range 50-70 GeV by the power law I(E, theta )=KE-2.09(cos theta )-0.02 where E is expressed in GeV, theta is the angle to the vertical and K is a constant. The above values of energy and cosine exponents are found to be in agreement with those calculated using the CKP interaction model if pions are assumed to be the parents of the majority of muons reaching sea level with energies in the range considered. Calculations made for various energies using this model also show general accordance with the experimental results of other authors. This indicates further support for the application of the model to primary interactions at high energies.

Cosmic-ray propagation in the atmosphere

An essentially analytical theory of atmospheric cosmic-ray propagation is developed on the basis of a phenomenological model of hadron-nucleus collisions. This model correctly predicts the sea-level cosmic-ray nucleon, pion and muon spectra, the cosmic-ray ionization profile in the atmosphere, and neutron flux and density profiles in the atmosphere. It is concluded that the large-scale properties of atmospheric cosmic rays can be accurately predicted on the basis of a purely nucleonic cascade as a result of which all secondaries are mediated by pion production. Implications for energy independence of cross-sections, the recent 70 GeV results from Serpukhov, and nucleonic relaxation rates in the atmosphere are discussed.

Cosmic-ray muon spectra near 1000 GeV at large zenith angles

Measurements have been made of the cosmic-ray muon spectra at large zenith angles using an optical-spark-chamber magnetic spectrometer with a maximum detectable momentum estimated to be 830 GeV/c. Absolute values of energy spectra up to 200 GeV were obtained at 75°, 80° and 85° zenith angles; differential and integral energy spectra approaching 1000 GeV have been evaluated at a zenith angle of 80°. The results are in reasonable agreement with previous magnetic-spectrometer data, and with expected variations in energy and direction for muons arising chiefly from pion sources. No evidence was found for dominant kaon or « X-process » muon sources in the 1000 GeV region. There is also no evidence for any elongation of pion lifetime which would be expected if special relativity broke down at distances less than 10−16 cm.

The dependence of muon intensity on the geomagnetic latitude

The vertical momentum spectrum of cosmic-ray muons has been determined by a counter controlled neon-hodoscope in the spectral region (0.2–3) Bev/c at geomagnetic latitude 12 °N. The observed spectrum agrees satisfactorily with the calculated spectrum of Olbert for muon momentum above 1.8 Bev/c. Below about 1.8 Bev/c, the measured spectrum exceeds slightly the theoretical spectrum of Olbert, calculated for the same geomagnetic latitude. The measured spectrum agrees with the experimental spectrum of Allkofer at 9 °N, but is somewhat below the spectrum obtained by Hayman in the low momentum region at 57.5 °N. This shows that there exists a latitude dependence of the low momentum muon spectrum.

Momentum spectrum and charge excess of cosmic-ray muons at large zenith angles

A large-momentum spectrograph with 100 cm2 sr aperture was used to measure the momentum spectrum and charge excess of cosmic-ray muons at zenith angles close to 75°. Preliminary results based on a small sample of events agree well with available data.

Spectrum of High-Energy Cosmic-Ray Muons at a Zenith Angle of 75°

The energy spectrum of high-energy cosmic-ray muons was measured at an angle of 75\ifmmode^\circ\else\textdegree\fi{} from the vertical. The results show that the direct muon production inferred from underground measurements of muons with energies over 1000 GeV is not observed in these spectrograph measurements at energies up to 300 GeV.

Das Impulsspektrum der Ultrastrahlungs-Muonen und das Ladungsverhältnis in 5200 m Höhe

The momentum spectrum of cosmic ray muons and the charge ratio at 5200 m above sea level have been measured. To separate the spectrum of muons from the total spectrum a lead absorber was used. From theoretical models the spectrum of muons is calculated. Good agreement is found between the calculated and measured muon spectrum.

The spectrum of high energy cosmic ray muons

A variety of studies have been made of the energy spectrum of cosmic ray muons. For energies up to 1000 GeV magnetic spectrographs have been used and at higher energies indirect measurements have been made. Inconsistencies between the results of the various experiments have been reported and these are the subject of the present paper. The differences are resolved and an estimate of the spectrum is made for the energy range 20-7000 GeV.

Energy spectrum of cosmic-ray muons at sea level

The integral energy spectrum of cosmic-ray muons at sea level in the energy range (200÷7500) GeV is deduced from the results obtained by us (as reported in an earlier paper) on the variation of vertical cosmic-ray intensity with depth in the range (800÷8400) m w.e. In doing this, the effect of fluctuations in the energy losses of muons is taken into account. The deduced muon energy spectrum is compared with direct magnet spectrograph observations and with the muon energy spectrum deduced by the Bristol group from their observations on γ-ray cascades at high altitudes. The exponents of the integral production spectra of parents of muons are given and an upper limit to the energy losses of muons in nuclear collisions is set.

The rate of energy loss of high-energy cosmic ray muons

The rate of energy loss of muons is examined by com paring the observed depth-intensity relation with that predicted from a knowledge of the sea-level energy spectrum of cosmic ray muons. The evidence for each of the parameters entering into the analysis is assessed and estimates are made of the sea-level muon spectrum up to 10000 GeV and the depth-intensity relation down to 7000 m.w.e. The effect of range-straggling on the underground intensities is considered and shown to be important at depths below 1000 m.w.e. Following previous workers the energy loss relation is written as -d E /d x =1.88+0.077 in E ' m / mc 2 + b E MeV g -1 cm 2 , where E ' m is the maximum transferrable energy in a /i-e collision and m is the muon mass. The first two terms give the contribution from ionization (and excitation) loss and the third term is the combined contribution from pair production, bremsstrahlung and nuclear interaction. The best estimate of the coefficient b from the present work is b = (3.95 + 0.25) x 10 -6 g -1 cm 2 over the energy range 500 to 10000 GeV, which is close to the theoretical value of 4.0 x 10 -6 g -1 cm 2 . It is concluded that there is no evidence for any marked anomaly in the energy loss processes for muons of energies up to 10000 GeV.

The Momentum Spectrum of Cosmic Ray Muons at an angle of 80 to the Zenith at Sea Level

A magnetic spectrograph making use of deflection in a `solid iron' magnet has been used to measure the differential momentum spectrum of cosmic ray muons at sea level for zenith angles close to 80° over the momentum range 1.5 to 40 GeV/c. The measured spectrum is close to that expected if all the muons come from pions. An analysis is made of the spectrum expected on the basis of muons being derived from charged kaons and conclusions are drawn about the rate of production of charged kaons under certain restrictive assumptions.

Measurements of the Momentum Spectrum and Charge Ratio of Cosmic Ray Muons at Sea Level in the Momentum Range 10 GeV/c-1000 GeV/c

The momentum spectrum of single cosmic ray muons arriving at sea level in the north-south plane at 57° N geomagnetic latitude has been measured for near vertical incidence. Results are given which cover the momentum range 5 GeV/c<p< 1000 GeV/c, and together with the earlier work of Owen and Wilson form a continuous spectrum from 0.5 GeV/c to 1000 GeV/c. The high momentum work is based on 1800 particles of momentum greater than 10 GeV/c.