Re: Threshold and Sampling Fraction

[Elke-Caroline Aschenauer <elke@jlab.org>]

On Tue, 29 May 2007, Matthew Shepherd wrote:

Dear all,

I would like to share some of my impressions on our meetings.
I think we have slightly to change something in the format of the meetings
to make them more useful.

I know some people are working already a longtime on the project, but in
the last month you have got three new people (Beni, Sergey and me) and
hopefully we will get more new people very soon.
In general getting new people in a group of people working together since
a long time is always a burden, but there is also the possibility for a
benefit as the new people look to things unbiased and might have
experience which might be helpful.

But to make it at all possible for the new people to participate some
minimum information has to be provided.
I give some examples:

-- what was simulated
-- what are the cuts used
-- what conditions required for a the histogram shown in addition to the
   cuts above
-- which data set was used
-- what have been the conditions/setup
-- what calibrations have been applied and how
-- ....

I think you get the idea some basic information so everybody starts from
the same knowledge.
If discussions in a smaller round happened it would be good to summarize
them for the rest of the audience.

Concerning MC and data plots, I personally think and I have taught that
all my students, it is bad to the final product after all corrections
especially if it shows problems. So I think even if some of you have seen
the basic plots already to often it might help to convince the newcomers
there is not something wrong with the base input.

I would really appreciate a lot if we could follow some of the
suggestions.

bye elke






> Date: Tue, 29 May 2007 16:56:44 -0400
> From: Matthew Shepherd <mashephe@indiana.edu>
> To: Richard Jones <richard.t.jones@uconn.edu>,
>      Zisis Papandreou <zisis@uregina.ca>
> Cc: halld-cal@jlab.org
> Subject: Threshold and Sampling Fraction
>
>
> Hi Richard and Zisis,
>
> It seems we can already take Blake's parametrization for the sampling
> fraction and sampling fraction variance and code this up into GEANT
> to introduce the fluctuations.
>
> The key remaining issue then is how do we set a realistic threshold
> for the MC?  We know from George that roughly 26 keV of energy in the
> fibers gives 1 PE.  So we need to understand what the SiPM readout is
> capable of separating from pedestal, correct?  Any thoughts on what
> this number is?
>
> Of course this involves things such as electronics noise and maybe
> even the specifics of how the fADC processes event buffers to pick
> out signals.  As a starting point, I wonder if it is it possible for
> us to begin to make a reasonable estimate (in terms of "photo-
> electrons") what the fADC threshold is.
>
> I'm not sure if we need a phone conference to do this or not -- maybe
> we should exchange some ideas on setting the threshold through email
> and see where we get.  Others on the halld-cal list may have ideas.
>
> -Matt
>
>
>

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