Cut efficiency correction

Efficiencies for the time cuts can be determined by making similar cuts in the full Monte Carlo time spectra. For this purpose, we used the standard SMC input with modified low energy formation rate (the nominal input, see Section 8.3). For the comparison with various Monte Carlo calculations with different physics input, we will be applying the same time cuts between the MC and data, hence the time cut efficiencies cancel out as long as the MC correctly describes the fusion time spectrum (not necessarily the absolute yield).

For energy cut efficiencies, we have used a dedicated Monte Carlo code, APEC-97 (Alpha Particle Energy Computation ver. 1997), featuring a package PEPPER (Profile Evaluation Package for Particle Energy and Range). An example of the APEC-97 outcome is illustrated with and without the use of PEPPER in Fig. 8.13. APEC-97 with PEPPER assumes the fusion depth profile calculated by SMC, while APEC-97 without PEPPER uses a uniform fusion profile.

It is interesting to notice that the simple uniform fusion depth profile (without PEPPER) seem to describe the observed Si spectrum better than the profile derived from a detailed full simulation of the muonic processes leading to fusion (with PEPPER). This might be due to real physics, but from these data alone we cannot exclude other possibilities such as non-uniform target layers (which is only included as the effective average thicknesses, see Section 6.1) or an inaccurate assumption of beam radial distribution.

Nonetheless we take the average of the cut efficiency derived from each depth profile, and take the difference as a measure of uncertainty. The derived energy cut efficiencies, together with various other corrections, will be given later in Table 8.13.