The Tkr hit multiplicity has been observed to exceed significantly that predicted by the Monte-Carlo simulation. This effect has been attributed to low-energy secondary electrons
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of the spectrometer in the beam amounting to more 10% X0 (red, run 811), for a run with the arm out of the beam (purple, run 916) and for the Monte-Carlo simulation (blue, run 122).
The three panels correspond to total hit multiplicity (top), hit multiplicity for thin (middle) and thick layers (bottom). The beam is 5 GeV electrons.
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