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Re: Attenuation length for GEANT
Hi Elke,
See answers below:
On Jan 29, 2008, at 6:51 PM, Elke-Caroline Aschenauer wrote:
> But I have a question which I have asked several times already if we
> run
> muons through the detector and compare the results we get for the
> geant
> based simulation for energy and timing resolution, do we come close to
> what was measured in the bcal test beam or for the current cosmic
> tests
> in regina.
Zisis, Alex, or George would probably be best to answer this. Note
that in the mainstream simulation we haven't yet incorporated light
yield and threshold information from the current, most accurate,
cosmic tests done with SiPMs into the simulation mainly because this
info is quite fresh. After the review, we plan to go back and do all
of this, but it seems like the changes aren't quite so drastic.
> The attenuation length of the FCal has a big impact on the light
> output
> and such what the lowest energy photons we can see. Can we really
> neglect
> all this issues if we have a final design review and want to show our
> detector has the performance we need.
Changing attenuation length from 166 cm to 90 cm as suggested by
Richard's notes according to my estimate corresponds to a degradation
in light yield of about 10% for showers that peak in intensity in the
middle of the block. Seeing as how Mihajlo recently changed the per
block threshold in the FCAL from 100 MeV to what we think might be a
better estimate of 30 MeV (although admittedly still under
investigation) and noticed only small effects in reconstruction
efficiency for physics channels such as eta pi0. I think these
changes are at the level of other uncertainties in our current
understanding of the FCAL simulation. For instance, we are proposing
a light coupling that increases the light yield by a factor of 2-3
from RadPhi, but again, this is based on study and simulation with
some notable systematic error. I'm not dismissing the need for a
better understanding here, but I don't necessarily think that the
attenuation length itself is the most pressing issue. In other words,
yes, I think it is safe to lump this issue in with others that need to
be addressed regarding FCAL performance. A full scale prototype with
the actual proposed light coupling and readout and/or a beam test
would be an excellent way to try to address these issues. This is why
we are enthusiastic about pursuing prototype and beam test studies.
Cheers,
Matt