sPHENIX EMCal discussion

[Edouard Kistenev <kistenev AT bnl.gov>]

Craig, 
here are my couple comments.

- nonuniformity can be factorized into light collection effects (potentially 
affected by fiber to light collector tilt/positioning), fiber density 
depletion on the block boundary, and by sawshape of the detector (difficult 
to factorize - it couples phi and eta coordinates). Data in p.5 confirm just 
this (caveat - with all tilts changed this comparison even for the in-block 
boundaries can be misleading). Subtract (quadratically) in-block 
nonuniformity from on-the-block boundary one and you will get at least an 
estimate to your nearly irreducible problem (saw shape). This problem is not 
in Oleg’s data, the rest are small tricks; 
- the phi boundary is much less affected by sawshape. Adjusting tilt may have 
positive effect but … what should be the tilt value. On the back of the 
envelope you need a tilt allowing shower center to move with respect to the 
fiber for the distance comparable to the width of affected area in your 
picture on one rad length of your active media depth (~50% of shower energy 
around shower max). This is very conservative but close (simulation will give 
better answer);
- are there “mechanical” solution to sawshape related nonuniformity. Maybe 
but first someone needs to try and deconvolute fiber density depletion from 
saw shape effect (can sawshape be approximated as a local change to fiber 
length?). There is exotic and technologically complicated solution to fiber 
density problem - shim the gap with two 0.5mm fiber bands, connect one to one 
tower, second to another tower). As for the sawshape - you know the answer 
only too well - elliptical shape (if 2D is a must) or 1D (with W  absorber 
and jets above pT~20GeV/c should be fine).

                        Edward


> On Apr 10, 2018, at 10:45 AM, Craig Woody <woody AT bnl.gov> wrote:
> 
> Dear All,
>   At today's EMCAL meeting, we will be discussing our readiness for the 
> EMCAL Block Design Review that will potentially take place later this week, 
> and also the status of the Sector 0 design. I've uploaded some slides to 
> the Indico page to guide the discussion so please have a look at them 
> before the meeting.
> 
> Many thanks,
> Craig
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