Re: Gondola effect test to do

[Tom Banks <tbanks@socrates.berkeley.edu>]

Hi Dave,

thanks for your critical thoughts on our current gondola effect
hypothesis.  We (Berkeley) are currently running an Ntuple analysis on
merlin specifically to investigate the possibility that a combined
diffusion+scattering mechanism may be responsible for the gondola
effect.  This analysis is performing some studies that are quite similar
in spirit to what you propose, although they differ slightly in the
details.

In particular, I have implemented upper/lower TPC per-gondola lifetimes.
The lower half of the TPC is closer to the primary scattering centers (the
2 aluminum supports running along the underside of the TPC), so you would
expect a more pronounced effect for lower mustops compared to the upper
mustops.  This is based upon the same idea you have discussed, that the
"near" mustops should see a larger scattering profile from the offending
structure than the "far" stops.

Some other studies: The aluminum supports also have a triangular shape,
and their thickness varies considerably over the length (Z-direction) of
the TPC.  Thus, one would expect a more pronounced gondola effect at
higher Z (the pressure vessel attachment point where the supports are
thickest) than at lower Z (closest to the window).  I have also
implemented lifetimes where the electron tracks *cannot* have passed
through cylindrical regions surrounding the aluminum supports.

Hopefully these will be sufficient to confirm or refute the hypothesis.
But I will certainly bear your idea in mind when the time comes for future
analyses.

Thanks,
Tom