Tags:
, view all tags
-- PeterKammel - 15 Feb 2007 * SET ALLOWTOPICCHANGE=Main.MuCapGroup

* SET ALLOWTOPICCHANGE=Main.MuCapGroup

TIIE distortions caused by wrong electron effect

TIIE is determined from the muon drift distribution.

TIIE (muSC+muPCX+muPCY)
Tom analysis rep obsolete
Tom corrected 8.
Steve new analysis rep 3.2

Tom's fast MC indicates a significant start time dependence of the fitted lifetime, which is not observed in the data? Tom pointed out that we don't have enough statistics to see this.

TIIE distortions caused by wall stop effect

The correction due to this effect scales with TIIE, in the same manner as the BB. Thus there relative importance is independent from TIIE.

Let us pessimistically assume TIIE= 8 ppm. The probability that a mu' fakes a good TPC stop after mu is TIIE * 0.63 * 21 kHz 0.024 ms = 2.5 ppm

Thus a contribution P(te-tmuSC)* 2.5 ppm is added to the undisturbed time distribution. According Tom's report, the most dangerous components are P(te-mu)= ... + 0.03 exp(-t/854ns) + 0.08 exp (-t/151ns). The total distorting amplitudes thus are 0.08 ppm for Al and 0.2 ppm for Fe, which should be ok.

TDIE distortions caused by wall stop effect

According to Tom's estimate TDIE=126 ppm. I.e. the wall stop effect is 15x larger than for the TIIE case. Such a contribution would lead to 10 Hz start time sensitivity of the fitted lifetime.

Tom's later studied indicate show that this effect scales with the deadtime for deadtime <200 ns.

But Steve does not see the expected 100 Hz effect in the start time fits with 150 ns artificial deadtime nor does he find a change of the fitted lifetime of more than 3 Hz. Thus the TDIE seems to be at least an order of magnititude smaller than estimated by Tom.

Tom's evidence of deadtime in the drift plots comes from Figures 11 and 12 of his 5/9/06 report. I don't quite understand these figures, but it seems to me that a 8 ns deadtime cannot generate a long step in the spectra. Moreover, it is hard to trust such an analysis anyway, because we don't understand the tail at the end of the drift distribution.

Locally we discussed 3 potential sources for such a tail:

  • TDIE due to mPC in the us range
  • Long drift times for poor field drift paths in the TPC
  • Physically later events (capture ...) misidentified as mu stop.
These speculations are for the record only, no need to investigate that for run8.

Dangerous wall stop fraction

I did a quick study to determine the dangerous wall stop fraction. Assume that, for whatever reason, a fraction f_sup of incident muons stopping on the wall gets accepted. What is their effect on the lifetime?

For the study I used Tom's parametrization of the muSC/muPC1 - eSC 25 us PP time spectrum from his muon detector inefficiency study, add this spectrum scaled by f_sup to the nominal spectrum and fit with a 3 par fit. We should check how Tom's fit changes for impact cut constrained tracks.

The input parameters were: repeat=100 Stat=1.0e+11 fit stop=24.00 acc=1.0e-03

f_sup del_lambda (Hz) del_lambda (Hz)
(E-3) start=0.1 us start= 0.2 us
10 81 67
5 40 34
1 7.8 +- 0.2 7.2 +- 0.2
0.5 4.3 +- 0.2 3.4 +- 0.2

The fit residuals for f_sup=5E-3 are shown below.

c1.gif

For a TDIE effect one has to account for this component (mu-e) and the smeared out one (mu-e'). The latter one is not accounted for in this study. Let us estimate the f_sup, for the case of TIIE and TDIEs.

overall TIIE R (kHz) drift (ms) +MWPC f_sup (ppm)
1.00E-02 21 0.024 5040.0
1.00E-03 21 0.024 504.0
1.00E-04 21 0.024 50.4
|muSC |TDIE deadtime(ms)
  1. 10E+01 21 1.00E-05 0.1 21.0
Topic attachments
I Attachment History Action Size Date Who Comment
GIFgif c1.gif r1 manage 26.3 K 2007-02-16 - 17:43 PeterKammel  
Edit | Attach | Watch | Print version | History: r6 | r4 < r3 < r2 < r1 | Backlinks | Raw View | Raw edit | More topic actions...
Topic revision: r2 - 2007-02-16 - PeterKammel
 
  • Edit
  • Attach
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2020 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback