sPHENIX is a new detector at RHIC.

[Aaron Angerami <angerami AT cern.ch>]

Hello Dave and Gunther,

I have a few  general remarks and some comments on some of the details. 

-The studies were the best that could done within the current constraints, but at the present time.  I think there is still a lot of uncertainty regarding how these changes will impact our ability to do jet measurements and that an acknowledgement of this fact should be included in both the executive summary and the last section. Right now, the take-away message is that there is a reduction in performance but that it is manageable. I suggest an adjustment of this message to say that this is what our current studies indicate but more detailed studies (lower pT jets, in Au+Au collisions, w/ more realistic relationship between GEANT output and calo energies) are required to understand the full impact of these detector modifications. I think it is important to articulate such a risk to the ALD in response to this charge.

-We show a quantitative impact on performance, but it would be helpful to first explicitly state why the descoping scenarios result in reduced performance. The natural place would be before L67. There is both the impact of reducing the interaction lengths as well as losing information about longitudinal profile of the energy deposition. The latter will be a limiting factor in how much we can achieve (improved JER) with a more advanced calibration procedure have a tangible impact on our ability to separate contributions from the UE vs those from a jet. 

Some specific comments:

L87:  I don’t know what quoting the JES values accomplishes here. The reduction in the JES can, and in practice is, always be fixed with an overall energy scale calibration. In this case the reduction in the JES is only significant insofar as it means a larger calibration would be required, this may translate into a larger JER or larger systematics, but that depends on the details of the calibration.

L88: “uncertainty” -> “statistical uncertainty”, unless I’m misunderstanding something here.

L94: As discussed in the jet TG meeting, the efficiency is a strong function of the minimum pT cut used to select jets; inefficiency arises because the low side of the response distribution causes jets to be measured below the nominal cutoff and the efficiency is the integral of the response distribution above this cut. I thought the conclusion of that discussion was that the apparent lack of an effect in Fig. 1.3 was because there was no minimum pT cut applied. If a cut is applied, it should be stated in the text. To demonstrate the fragmentation dependence, a plot of the JER vs leading z would be far more general and effective.

Best,

Aaron

From: Jamie Nagle <jamie.nagle AT colorado.edu>
Date: October 23, 2017 at 12:42:52 PDT
To: "sphenix-l AT lists.bnl.gov" <sphenix-l AT lists.bnl.gov>
Subject: Re: [Sphenix-l] [sPH-GEN-2017-002] Collaboration comments on 2017 descoping document

Hello Dave and Gunther,

I think the document reads well and makes the key points clear.   I have just a couple of remaining suggestions.

Sincerely,

Jamie

1.    One might want in the Executive Summary to state what the charge is and a date for that charge...  The charge is specific to address the $38M baseline as shown in the August 2017 review and present a re-scoped baseline of $32M.   Then you can say that the $38M baseline is shown in Table XX, and the re-scoped option at $32M in Table YY.   Including the dates is important.

2.   On the jet performance, I realize we have gone back and forth on this quite a bit so I want to include a positive request.   The sentence starting on line 89:

"Further studies indicate that the lost performance can be recovered (or even 

improved compared to the calorimeter-only jets in the nominal configuration) through an optimal combination of calorimeter and track based information, following, e.g., the particle flow algorithm used in CMS and ILC jet reconstruction."

I believe the statement is not factually correct, since only an algorithm without pulling truth information can demonstrate this point.   I have a sentence suggestion below.

"Future studies utilizing an optimal combination of calorimeter and track based information follow, e.g. the particle flow algorithms used in CMS and ILC jet reconstruction, may recover (or even improve) the calorimeter-only jet performance in the nominal configuration.    This avenue is particular important to pursue as removing a longitudinal segment of the calorimeter reduces key cross checks such as a jet response as a function of longitudinal center-of-gravity of the shower."

I think it is important to not leave a sentence that can be used to undermine recovering the full scope in sPHENIX.

Sincerely,

Jamie 

On Mon, Oct 23, 2017 at 10:37 AM, John Lajoie <lajoie AT iastate.edu> wrote:

Hi Martin,

    Good eye - the fragmentation plots have been updated with additional statistics at high-z since they were shown at the last GM. That makes the statistics kind of funny, so I think it's better plotted with the errors - see attached replacements for Fig. 1.3 with the error bars shown.  I think these show more clearly that any deviations from the SS310 efficiency as a function of leading z are small in both configurations.

Regards,
John

On 10/22/2017 9:44 AM, Martin Purschke wrote:

All,

nicely written document! Some remarks...

I cannot claim that I have been at every meeting, but I don't recall
seeing the 15%-ish *increase* in efficiency in Fig 1.3 (right) at low z
values. This large difference just between the instrumented and
non-instrumented setups (where no instrumentation seems better) is
somewhat counter-intuitive to my eye.

Rosi presented John's distributions in slightly different form at the
Oct 6 fortnightly meeting, and there it looked less pronounced (in both
cases the green curve). Also there the low-z enhancement was in the
charged leading particle plot, neutral was flat, opposite of fig. 1.3.
Is there a simple explanation why one would expect that?


In line 114 the arrow in Y-> e+e- points the wrong way.

My 5cts,

	Martin


On 10/21/17 00:02, Gunther M Roland wrote:

Friends,

As discussed at the General Meeting today, we are forwarding draft 1 of our document outlining the detector scope for a $32M cost cap. The pdf file can be found at 
https://www.dropbox.com/s/5wyutbndogozm5q/sPH-GEN-2017-002_v1.pdf?dl=0
(we'll provide another link tomorrow for those that can't access dropbox)

Please send your comments in reply to this mail, keeping the [sPH-GEN-2017-002] tag in the subject line***. Comments received by close-of-business on Monday, 10/23, will be most useful. 

Cheers,

Gunther and Dave

***we will move future reviews to an sphenix-notes-l AT bnl.gov list, but the list couldn't be generated in time for this note.
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John Lajoie

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Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie

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