Knockon Electrons

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Cosmic Ray Observatory Project University of
Nebraska - Lincoln
Mount Michael High School
Knock-on Electrons
Brett Stempel David Levy Dan Olson
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Experimental Results Spring 2001
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Experimental Results Spring 2002
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Why the change in slope?
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A muon with sufficient energy knocks an electron
knocks out of its path. The knock on electron
may also have enough energy to be ionizing.
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Conservation of Energy mmc2/ ?(1 v2/c2) mec2
mmc2 / ?(1 u2/c2) mec2 / ?(1
w2/c2) Conservation of Momentum mmv/ ?(1
v2/c2) mmu/ ?(1 u2/c2) mew / ?(1 w2/c2)
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Maximum kinetic energy transferred from an
ionizing muon to an electron
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Average energy of a muon produced by cosmic rays
at the earths surface is 4 GeV. So knock on
electrons might be expected to have a maximum
kinetic energy of about 1 GeV.
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Knock on electrons appear to have limited lateral
range. Dr James Cronin suggested the following
experiment to detect knock on electrons
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Double Coincidence Side by Side
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Double Coincidence Side by Side
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Double Coincidence On the Diagonal
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Double Coincidence On the Diagonal
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Diagonal - EF Mean 77.9 GH Mean
84.7 Side by Side - EF Mean 201.6 GH Mean
166.7
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Conclusion
Detectors connected side-by-side see about twice
as many counts as detectors connected diagonally.
Knock on electrons are responsible for increased
counts at small detector separation.