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The nature of statistical fluctuations with applications to cosmic rays

Evans, Robley D. and Neher, H. Victor (1934) The nature of statistical fluctuations with applications to cosmic rays. Physical Review, 45 (3). pp. 144-151. ISSN 0031-899X. doi:10.1103/PhysRev.45.144.

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I. The square of the mean deviation D of the combined effect of several random processes releasing an average of x, y, z ... particles per unit time and producing a, b, c ... ion pairs, respectively, per particle, is D2=a2x+b2y+c2z+..., regardless of whether the separate effects are added or subtracted by the experimental arrangement. For tube-counters, point-counters, scintillation screens and particle counting chambers, a=b=c=1; for ionization chambers a, b, c ... are unequal. II. From the standpoint of statistical fluctuations, the use of two identical instruments in a differential circuit is inferior to the use of a single instrument. III. The natural observational limit for the measurement of x particles against a background of y particles is x=0.67(y)1/2. IV. The statistical fluctuations in the ionization produced by cosmic rays in a spherical ionization chamber are treated rigorously and the fluctuations due to heterogeneity of range and to showers are derived. V. Application to existing data shows that the showers observed in cloud-chamber photographs of the cosmic radiation are also present in the ionization chamber in about the same frequency and multiplicity as indicated by the cloud-chamber results. The tube-counter investigations of the cosmic-ray flux are also in agreement with the deductions from the statistical fluctuations in the ionization chamber. An upper limit of 70±10 ion pairs per cm in air at 1 atmosphere is set for the total ionization along the path of an individual cosmic-ray secondary. The size and the relative frequency of occurrence of showers is appreciably greater at 14,700 feet elevation than at sea level. These showers are quite distinct from the ionization bursts or Stösse observed by Hoffmann, Steinke and others.

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Additional Information:©1934 The American Physical Society. Received 27 November 1933. The theoretical work was done by the first of the authors, the experimental work on cosmic rays by the second. The authors record their thanks to Professors H. Bateman, R. T. Birge and J. R. Oppenheimer for reading the manuscript and to Professor R. A. Millikan for permitting us to use the facilities and the data developed and accumulated by himself and his associates, through the aid of a grant made by the Carnegie Corporation of New York, administered by the Carnegie Institution of Washington, for the support of his cosmic-ray researches. [R.D.E. was a] National Research Fellow.
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5388
Deposited By: Tony Diaz
Deposited On:16 Oct 2006
Last Modified:08 Nov 2021 20:25

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