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-- PeterKammel - 17 Feb 2007
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During the unblinding meeting I expressed my concern about known and unknown potential wall stops, which are not eliminated by the TPC good stop definition (see the slide below).


After fitting simulated m-e time distributions after muSC/muPC in MuDetUpdate, we are in a better position to quantify this effect. We discuss three posibilities as shown in the slide.

TPC misreconstruction

This refers to the situation that the muon stops outside, but still generates a valid muon signal in the TPC. The only physical model we have is the mu+p scattering process, which we have studied extensively.

undetected pile-up

The fit of the generated time spectra indicates that we can tolerate ~100 ppm probablity for this to happen as this shifts the lifetime by less that 1 Hz. The estimates of undetected pile-up effect both due to TIIE and TDIE is below 100 ppm. The TDIE effect was enhanced in Steve's muSC deadtime study.

noise in TPC

We have not analyzed this directly. Let us try to get a rough estimate from the muPC+mPCX+mPCY TIIE= 3-8 ppm. If we assume that the pile-up protection is perfect, than we could attribute this TIIE to noise in the TPC misidentified as good stops. Such a noise contribution would not lead to a Banks Bump, but to an identical wall stop effect as estimated for the standard TIIE. So it is already accounted for.

All the wall stop effects above arise from TPC good stop signals generated not by the muon stopping in the wall, but by other sources. Thus the mu-e impact parameter should supress those. Moreover, wall stops increase the fitted rate. Accordingy, wall stops are not suitable to explain the observed difference between 120mm and no impact par cut fit results.

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