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Re: comments on the resolution floor term



Dear all,
let me add my thoughts on the floor term.First of all I think that
additional material upsteam will add to it (it is not clear to me that
this will scale with root(E))>but probably not relevant for our case at
the test beam.
Other very important factors which really shows up in the floor term are
the mechanical imprefections.For example a 1%variation of the thickness of
the Pb-plates in ATLAS (which are 2.2mm) leads to a 0.7% of response
drop.So in ATLAS the thickness was kept to within a sigma of 9microns!!How
accurate was ours?Were they made by the same company as KLOE's??etc
etc.How uniform was the gap kept?
                       Cheers,Christine
 > Hi Elton:
>
> While the leakage to the back of the BCAL and KLOE are indeed nearly
> identical, during the tests we used one module that allows approximately
> 2.5-3% leakage from top and bottom (in reality out the sides).  KLOE has
> not such problem because in beam tests of single modules they have the
> advantage of much bigger modules while from the performance of the KLOE
> as a detector, this of course does not play a role.
>
> I see this as the only difference in conditions that may raise issues.
> The gain matching of the PMT's and the response of the light guides do
> not introduce variations that may justify larger floor terms for us.
>
>
> Cheers,
>
> George
>>>> Elton Smith <elton@jlab.org> 05/08/07 12:31 PM >>>
>
> collaborators,
>
> A couple of comments occurred to me after the meeting this afternoon
> regarding the resolution floor term. In comparing our results to KLOE we
> have been making the implicit assumption that we expect similar
> resolution. This should be expected for the shower fluctuations, because
> it is dominated by geometry and the GlueX and KLOE calorimeters are very
> similar. However, the expectation for the floor term may be different.
> This term is dominated by systematic contributions to either the energy
> or
> the timing. However, most contributions to the floor term (e.g.
> electronic
> noise, gain non-uniformity, etc) could in fact be quite different
> between
> the two detectors and we should not make that assumption. [See note 1].
>
> Cheers, Elton.
>
> [note 1] The exception is the shower leakage contribution to the floor
> term should be similar because of similar geometry and thickness (about
> 15X_0).
>
>
>
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite # 16
> Newport News, VA 23606
> elton@jlab.org
> (757) 269-7625
>
>