In our stopping fraction measurements, most or all of the hydrogen was
placed on the upstream target, while the muon can stop in gold at both
upstream and downstream targets. The relative geometrical acceptance for
the electrons from hydrogen and gold is expected to be similar for the
counters at the sides (Ege, En1), but can be different for the downstream
counters (En2). Taking this into account, the expression for the stopping
fraction Eq. 6.5 should read:
If the beam momentum width is larger than the corresponding thickness of gold foils and the hydrogen layer, one would very roughly expect for the beam momentum optimized for the maximum stopping in hydrogen. can be roughly estimated to be about 1.3 for En2 from the fact that target spacing between the upstream and the downstream layers is some 12% of the detector distance. Assuming a point source, this would make about a 10% upward correction to SARH (from 25% to 27.4%) for the downstream counter pair En2.