An instructional laboratory experiment to measure the muon mass is described. Using coincidence-anticoincidence detection, the decay of a cosmic-ray muon into an electron (or positron) is observed in a multiplate spark chamber, and recorded with a triggered CCD detector. The energy of the charged decay-product particle is quantified by counting the number of spark gaps it traverses before being stopped by the chamber’s aluminum plates. By running this apparatus under computer control for several hours, the number of product particles with various -values is obtained. The muon mass is obtained by a least-squares fit of the experimentally observed to simulation values predicted for this distribution by the Fermi description of muon decay via the weak interaction. We present our results for the muon mass and discuss the simulation we developed to account for the observed skewing of due to the various directions the spark-producing product particles move as well as the escape of some of the higher-energy particles from the chamber.
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January 2010
PAPERS|
January 01 2010
Determining the muon mass in an instructional laboratory
Benjamin Brau;
Benjamin Brau
a)
Department of Physics,
University of Massachusetts, Amherst
, Massachusetts 01003
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Christopher May;
Christopher May
Department of Physics,
Reed College
, Portland, Oregon 97202
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Robert Ormond;
Robert Ormond
Department of Physics,
Reed College
, Portland, Oregon 97202
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John Essick
John Essick
b)
Department of Physics,
Reed College
, Portland, Oregon 97202
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a)
Electronic mail: bbrau@physics.umass.edu
b)
Electronic mail: jessick@reed.edu
Am. J. Phys. 78, 64–70 (2010)
Article history
Received:
June 26 2009
Accepted:
August 26 2009
Citation
Benjamin Brau, Christopher May, Robert Ormond, John Essick; Determining the muon mass in an instructional laboratory. Am. J. Phys. 1 January 2010; 78 (1): 64–70. https://doi.org/10.1119/1.3230034
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