Si1-Si2 symmetry

Generally, higher count rates were recorded in Si2 compared to Si1. This is presumably due to the higher background rates, as Si2 was geometrically slightly closer to the beam axis. However, as was seen in Tables 8.4-8.6, the background subtracted yields are mostly consistent with the Si1-Si2 symmetry, except when the signal-to-noise ratio is low as in 3 T$\cdot l$ TOF measurements where we observed up to 30% asymmetry. We note, however, that while the individual detector yield can be sensitive to a slight shift in the beam position, this effect is cancelled in the averaged yield to first order. For example, in the limit of a small beam size, a 5 mm shift in the beam can cause some 40% asymmetry in the individual detector yields, yet the averaged yield is affected only by a few percent. Therefore it is crucial to have two detectors particularly for the absolute yield determination.