Meters Water Equivalent Research Articles

Muon intensities and angular distributions deep underground

Recent measurements of the intensity of muons below 3000 m.w.e. (metres water equivalent) underground have been combined to give an estimate of the depth-intensity relation and the angular distribution for atmospheric muons down to a maximum depth of approximately 9000 m.w.e.

The intensity and angular distribution of cosmic rays far underground

An apparatus incorporating scintillators, Geiger counters and neon flash-tubes has been operated at three locations underground in the Kolar Gold Fields, India, to measure the vertical intensity and angular distributions of penetrating cosmic-ray muons. The intensities at the three depths (816, 1812 and 4100 metres water equivalent of rock) are, respectively; (2.39 ± 0.15) × 10-6, (2.00 ± 0.12) × 10-7 and (4.63 ± 0.57) × 10-9 cm-2 sec-1 sterad-1. The angular distributions are well represented by expressions of the form I(θ) = I(0)cosnθ, where θ is the zenith angle, and the values of n at the successive depths are 1.93 ± 0.22, 3.03 ± 0.16 and 5.12 ± 0.82.

Decay of a Tau-Meson Underground

THE decay of heavy cosmic ray particles underground has been reported by Higashi et al. 1, and L. and M. Avan1. Higashi found a neutral V-particle in a multiplate cloud chamber at a depth of 40 metres water equivalent underground. The V-particle was produced by a shower secondary from a large interaction in the chamber. Avan, using glass-backed emulsions at a depth of 300 metres water equivalent, reported the decay of two K-mesons, one of which was produced in the glass backing of an emulsion.

The Momentum Spectrum of -Mesons at a Depth of 40 Metres Water Equivalent

Scattering distributions, obtained in two lead plates, each 2 cm thick, placed in a cloud chamber situated at a depth of 40 metres water equivalent, have been used to determine the momentum spectrum of μ-mesons in the range 0.22-1.0 GeV c-1. The spectrum is in good agreement with the spectrum derived from the sea level data of Holmes and co-workers.

On the interaction of μ-mesons with matter at high energies

The production of penetrating showers at depths of 50 and 200 metres water equivalent by high energy μ-mesons has been studied with a counter hodoscope. The values of the cross-section found (in lead) for events of this kind are consistent with those expected assuming an electromagnetic interaction mechanism, according to which the penetrating showers can be initiated by the photoproduction of a π-meson or by a high energy recoil nucleon. The agreement between the measured and calculated cross-section is very good, if it is assumed that the total photonuclear cross-section, σγtot = 3·10−28 cm2/nucleon, remains unchanged even at the high energies concerned at the depths considered. Therefore it seems unnecessary to invoke a new interaction in order to explain the experimental results.

On the interaction of cosmic rays with matter under 50 metres water equivalent

The production of penetrating secondaries by cosmic rays at 50 m w.e. has been investigated by means of a counter hodoscope. The cross section (in lead) for events which can be interpreted as pairs of associated penetrating particles (a.p.p.) is not larger than (13±3)·10−30 cm2/nucleon. Such a value is deduced from measurements of the corresponding differential cross section as a function of the penetration of the secondary particles produced (section 4·3 table V). A value of the same order of magnitude is found for the production ofa.p.p. in rock (section 4·5). Furthermore it is shown that the events that can be interpreted as showers penetrating 15 cm Pb, have a frequency that can be explained, at least in part, as due to purely electromagnetic interaction. Therefore one can establish an upper limit of a few units in 10−30 cm2/nucleon for the cross section for production in Pb of penetrating showers by μ-mesons. Finally we discuss those events which appear to be due to a few penetrating particles coming from the rock and it is shown that they can be accounted for, by considering besides the production of penetrating showers in rock the penetrating particles present in the vicinity of the core of extensive air showers.

Cosmic-Ray Intensities at Great Depths

A fourfold Geiger-M\"uller tube telescope was employed to count the relative number of cosmic rays under different thicknesses of rock. Each Geiger-M\"uller tube consisted of a 0.125 mm tungsten wire anode and a cylindrical copper cathode 9 cm in diameter and 71 cm in length sealed in a glass envelope filled with hydrogen to a pressure of 9.6 cm of mercury. The experiment was performed in a mine whose shaft was inclined at an angle of 34\ifmmode^\circ\else\textdegree\fi{} from the horizontal. Counts were made at thirty-nine different stations at depths from zero to 1408 meters of water equivalent, where the rate was 5.7\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ as great as at the surface. When the intensity is plotted against the depth, the resulting curve shows no points of inflection. The effective absorption coefficient decreases from 0.07 per meter of water at the surface to 0.0025 at the greatest depth. If the logarithm of the intensity is plotted against the logarithm of the depth, two straight lines, one from 20 to 250 and the other from 250 to 1418 meters water equivalent from the top of the atmosphere, represent the data well. Shower counts were also made at ten of the stations. These also show a bend at 250 meters. This suggests that there may be two types of very penetrating rays both capable of producing showers. It may be that one of these consists of "heavy electrons" and the other of "neutrinos."