Since the Si data contains counts from non-fusion events as seen in the previous sections, subtracting appropriate background is important in the yield and spectrum determination. It is one of the advantages of our multi-layer film targets that the process of interest can be controlled, i.e., ``turned on'' and ``turned off'' without much affecting other processes (e.g., by simply depositing a thin layer), hence providing rather reliable means of background subtraction. Thus our strategy generally is to use the data from the target, in which the particular processes is turned off, for the background subtraction whenever possible (with both the signal and background data normalized to the number of muons GMU). For a given measurement, nonetheless, there were sometimes more than one possibility for the choice of the background runs, or no one best choice, in which case different methods were compared to see the systematic effects. Summaries of background runs used are given in Table 8.2. As we will see, in some cases further corrections were necessary to account for a residual background.
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