[Hps-ecal] few questions about ECal alignment

[Holly Vance]

I am already working on the resolution in Task 3. I'll check with varying
it by a few mm.

On Fri, Sep 4, 2015 at 8:24 AM, Stepan Stepanyan <stepanya at jlab.org> wrote:

> Dear all,
>
> There was a discussion at yesterday's software meeting about the ECal
> positioning.
> I want to ask if some of you can do quick studies of some issues to
> clarify few things.
> It might be that these questions have been already answered and someone
> knows the
> answers, or someone is in process of getting this resolved, so please
> share whatever
> you have with the group. Here are the questions:
> 1) what is the track extrapolated position resolution at the ECal?
> Basically I want to have have few thousands E=0.5 GeV e+ and e- be
> simulated in groups
> of fixed angles, phi and theta, and for each group distribution of X and Y
> positions
> at the calorimeter been studied. The field map can be anything, as long as
> it has stray
> field distribution
>
> 2) what is the effect of the ECal Y-position on the trigger performance?
> This simply can be the same studies Kyle does with the trigger, but with
> different
> Y-positions of the ECal. Kyle already has one fixed position studied, if
> he can do
> the same by moving top ECal by 1 mm, 2mm, 3mm ... and see how trigger
> efficiency
> to A's changes, then move both the same way. I want to understand how much
> ECal
> should be misaligned to effect our trigger.
>
> 3) what is the effect of the Y-alignment on the ECal energy resolution?
> Here the worry is that when we do sampling fraction corrections, that
> corrections
> depend on the position of the hit. Closer to the edges, e.g. in row 1,
> larger the
> corrections. Of course closer to the edges worse resolution we will have.
> Now one
> can derive sampling fraction correction as a function of hit position in
> row 1 using
> some geometry (nominal will work), then correct cluster energy by applying
> sampling
> fraction correction not for the position that cluster reconstruction
> algorithm is giving
> but shift it by 1 mm, 2mm , 3 mm ..., and look to see what is the energy
> resolution and
> compare to the nominal one.
>
> Please let me know if anyone can take any of these tasks and if there are
> questions
> on what is above.
>
> Thanks, Stepan
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