M R Whalley

Precise measurement of the vertical muon spectrum in the range 20-500 GeV/c

The 300 ton cosmic ray spectrograph (MARS) has been used to measure the vertical momentum spectrum of cosmic ray muons in the momentum range 20-500 GeV/c at sea level.

Mars II: The operation and elements of the spectrograph

Abstract The method of operation of the spectrograph - MARS - is described. The limitations of the triggering system, and of the method of storage of data from the flash-tubes are discussed. The momentum selector incorporated in the spectrograph is considered in detail, and it is shown that there is no rejection of events by the device due to the production of bursts in the iron blocks or to air showers incident upon the apparatus. The events are also considered by equipment which, if the data in the event is suitable, calculates the deflection of the particle traversing the spectrograph using the information available from the momentum selector.

The sea-level muon spectrum and charge ratio and their relationship with high-energy accelerator data

The sea-level muon spectrum and charge ratio have been calculated using the available high-energy accelerator data. The calculated muon spectrum is inconsistent with a primary nucleon spectrum of the form AE- gamma but is consistent with a spectrum of the form A(E- gamma 1+X0E- gamma 2). Consideration of the sea-level muon spectron and the primary iron spectrum suggests a primary nucleon spectrum 1.73 (E-2.70+or-0.05+1.35* 10-3*E-2.00+or-0.10)s-1 sr-1 cm-2 GeV-1. This spectrum is in better agreement with the observed muon charge ratio than a spectrum with a single exponent, but the predicted ratio is 7%in excess of the measured ratio at a sea-level momentum of 10 GeV/c, and this is attributed to a breakdown in the limiting fragmentation hypothesis or a difference in the charge distribution of secondaries between nucleon and nucleus targets. The predicted and observed variation of the ratio are in good agreement assuming that the spectrum of nuclei (Z approximately 26) cuts off in the region of 104GeV.

MARS I: THE GEOMETRICAL CHARACTERISTICS OF THE DURHAM MAGNETIC AUTOMATED RESEARCH SPECTROGRAPH.

Abstract The new 300 t vevertical spectrograph of the University of Durham are described. The spectrograph utilises neon flash-tubes for particle trajectory defining purposes and the data from the tubes are fed directly into an on-line computer. The m.d.m. of the spectrograph is 5850 GeV/c, and the ratio of the rms scattering angle to the magnetic deflection is 10%. A momentum selector is incorporated in the instrument with a low momentum cut off of approximately 200 GeV/c. The value of ʃB d l is 8.09×10 6 G cm , and each of the two sides of the spectrograph has an acceptance of (408±2) cm2sr for particles of infinite momentum. The rate of transversal of muons through each side of the instrument is in excess of 2×104 per day.

ABSOLUTE INTENSITIES OF COSMIC RAY MUONS ABOVE 3.48 AND 7.12 GeV/c.

The new Durham spectrograph MARS has been used to determine absolute intensities of cosmic ray muons in the near vertical direction with momenta above 3.48 and 7.12 GeV/c. The intensities are found to be close to those previously reported by Aurela and Wolfendale in 1967, the present intensities being higher by some (7.7 ± 1.3)% and (1.7 ± 1.4)%, at the respective momenta. Comparison is also made with the results of other recent measurements.

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.

Interpretation of the charge ratio of cosmic ray muons

An examination is made of the charge ratio of near vertical cosmic ray muons at energies up to 2*1012 eV in the light of recent accelerator results. The results can be understood if the charge ratio of pions emitted with energy in the region of 20% of the primary proton energy is smaller for p-air nucleus than has been measured for p-p interactions. This result appears to contradict the strict application of the fragmentation hypothesis.

Particle location along the length of a neon flash-tube

Abstract Measurements have been made of the time delay in arrival and the amplitude of the digitisation pulses from both high and low pressure neon flash-tubes. The velocity of propagation of the digitisation pulse is 3.6 × 10 6 m s −1 for the low pressure tubes and 6.7 × 10 6 m s −1 for the smaller high pressure tubes. A qualitative explanation of the delay time is given. The results show that it could be possible to locate the initiating particle of the flash tube along the axis of the tube by timing techniques to approximately ± 10 cm.

Multiple scattering of cosmic ray muons in the range 10-70 GeV/c

The new Durham spectrograph, MARS, has been used to study the Coulomb scattering of cosmic ray muons in iron in the momentum range 10-70 GeV/c. The observed root mean square lateral displacement agrees well with that predicted to within the statistical errors, which range from 2% at the lowest momentum to 17% at the highest momentum. Averaged over the whole momentum range the ratio of observed to expected root mean square scattering displacement is 1.023+or-0.019.

An improved measurement of the charge ratio of cosmic ray muons in the range 10-300 GeV/c

The MARS instrument at Durham has been used to study the charge ratio of near vertical cosmic ray muons in the momentum range 10-300 GeV/c. No significant structure is seen and there is no firm evidence to favour a significant deviation from the mean value of 1.284+or-0.004. Including the results from the Utah detector, which correspond to muon momenta in the range 1000-2000 GeV/c, there is the suggestion of near constancy from 10 GeV/c to 2000 GeV/c.