Self correlations are effects where either the electron causes a change in the muon detection efficiency or the muon changes the electron efficiency. The largest effect of this type is that of the muon affecting the electron track within the TPC. Long tails after the muon track and the muon track itself can greatly alter the efficiency to find the 200 times weaker electron tracks. Even if we restrict electron tracks to angles which greatly reduce this self interference, secondary muon tracks and other electrons will cross on top of or near the electron track of interest and change the efficiency.
Though we have made electron tracking algorithms which
are near 100% efficient, we would need to guarantee that this
efficiency does not change by more than
to
achieve our goals. For this reason we have moved all electron
tracking outside of the TPC to achieve almost complete
muon-electron independence. Now for muons that have stopped in the
fiducial volume, the only way they could affect the detection
of their own decay electron is, if there would be some kind of
cross-talk between the TPC electronics and the electron
detector electronics (discussed below). We did not completely
dispense with electron tracking within the TPC, we still use
the reasonably high electron efficiency to assist in crucial
studies of diffusion, electron scattering and certain checks of
the external tracking.