sPHENIX discussion of physics

["Sickles, Anne M" <sickles AT illinois.edu>]

Hi,

As promised yesterday, here is some text for the EMCal segmentation 
discussion:

—

table 1.1: replace EMCal 2x2 ganging item with: "reduction in EMCal 
granularity (either through larger EMCal towers or 2x2 ganging of reference 
configuration towers)”

—

A.2 EMCal

suggest to combine A.2.1 and A.2.2 into a section “Reduction in EMCal 
Segmentation” with text as follows:

Cost delta: -$1.7 — -$1.8 M

We have considered two options to reduce the electronics cost associated with 
the EMCal by reducing the segmentation.  One is ganging together groups of 
2x2 towers in the reference configuration tower size (0.024 x 0.024, leading 
to an effective segmentation of 0.048 x 0.048) and the other is to make a 
permanent reduction in the EMCal granularity by making the towers bigger (one 
such configuration could be 0.033 x 0.028 in $\Delta \phi x \Delta \eta$).  
Larger towers would reduce the cost of the read out electronics, but would 
likely require increasing the number of SiPMs per tower to preserve the light 
collection uniformity. The advantage the second option is that this would 
provide a finer segmentation than the ganging option, however it would not 
allow the reference configuration segmentation to be recovered. The EMCal R & 
D to this point has focused on the production of towers of the 0.024 x 0.024 
size in the reference configuration.  Increasing the tower size introduces 
potential production issues in the tower construction and performance. 
Additional R & D will need to be done to determine if larger towers can be 
made as efficiently and uniformly as in the reference configuration and that 
the light can be collected from larger area lowers with sufficient uniformity.

Both reduction in segmentation options are estimated to be approximately the 
same cost savings and if this option is pursued we would like to pursue basic 
R & D on the larger size towers to address the concerns described above and 
based on those finding to decide which option provides the most feasible 
construction option.  This R&D would delay the overall EMCal schedule by 
approximately six months and might require additional prototyping beyond that 
which is currently in the schedule.

--

There is currently no text in A.2 about the EMCal reduced acceptance.  I 
propose adding a subsection:

Reduction in EMCal $\eta$ Acceptance

Cost delta: -$2M 

The reduction in EMCal acceptance would save the money associated with 
building the higher $\eta$ towers and their electronics cost.  The cost 
savings here is associated with reducing the EMCal coverage to $|\eta|<$~0.7. 
 This is an arbitrary choice and could be changed to achieve larger or 
smaller savings.

This is a potentially recoverable change, but it has schedule, design and 
engineering impacts.  If this change is to be recovered it must be 
anticipated enough into advance to preserve the feasibility of the recovery. 
The most time critical part of an acceptance recovery is to preserve the 
ongoing R&D for the two dimensional projectivity.    The motivation for the 
2D projectivity is the $e/\pi$ separation at high rapidity.  This R&D is 
making good progress and is the planned goal of the anticipated 2017 test 
beam.   Additional concerns to assure the feasibility of an acceptance 
recovery are ensuring that the EMCal support structure can support the weight 
of the full acceptance EMCal and ensuring that module production begins early 
enough that the full amount of modules could be constructed on a timescale to 
install them with the rest of the detector.

—

Best,
Anne





> On May 31, 2016, at 9:51 PM, Gunther M Roland <rolandg AT mit.edu> wrote:
> 
> Friends,
> 
> We have compiled "Draft 0" of the response to the ALD's charge. The 
> document can be found at:
> https://www.dropbox.com/s/ix032ws53rz3fhu/ALD_response_v0_20160531.pdf?dl=0
> 
> Please note that this is "Draft 0" and a lot of work remains to be done, 
> some trivial, some not. We expect that we will distribute new iterations of 
> the document every 24h, based on feedback and new information received, 
> with a final discussion at this Friday's fortnightly meeting. 
> 
> For this iteration, we are particularly interested on comments about the 
> general structure, key statements and, most importantly, careful checks of 
> the factual content, both in terms of cost savings and the description of 
> the performance studies. Careful spell-checking OTOH may be premature at 
> this point. Please keep in mind that the basic structure of a short 
> overview and extended appendices with details was requested by the ALD. 
> 
> The current document contains a large number of "FIXME" labels, where new 
> numbers or cross-checks by experts are required. Also, the tracking team is 
> running simulations with the VTX pixel and 2-layer MAPS inner tracker 
> configurations to be included in section B.4 and the HF topical group is 
> going to supply corresponding b-tagging performance plots.
> 
> We will meet with the ALD tomorrow afternoon, and expect to call an EC/TG 
> coordinator meeting late tomorrow afternoon to discuss comments, questions 
> and the final approach.
> 
> Please don't hesitate to send comments either to the list or privately, if 
> necessary.
> 
> Cheers,
> 
> Gunther and Dave
> _______________________________________________
> Sphenix-physics-l mailing list
> Sphenix-physics-l AT lists.bnl.gov
> https://lists.bnl.gov/mailman/listinfo/sphenix-physics-l



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Anne Sickles
Assistant Professor, Department of Physics
University of Illinois at Urbana-Champaign
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