Eic-dsg-l mailing list

["Lajoie, John G [PHYSA]" <lajoie AT iastate.edu>]

Dear EIC LOI Writing Group:

    First of all, my thanks to the detector study group that has put a great deal of work into producing the draft as it stands right now.

    I realize the amount of effort that goes into producing a document like this, but the current draft is very rough and incomplete.  In fact, language and editing issues get in the way of trying to evaluate the scientific content of the draft. Because of the important nature of this document, I believe it will require a revised release to the collaboration before it can be submitted to lab management.

    A few general comments:

-> It would help in offering comments and suggestions if the line numbering didn't restart in each page but you could refer to a unique line number in the document.

-> Some of the figures are not reproducing well or are of low quality (I'll try to note where below). In general when another editing pass is done the appearance and quality of the figures should also be checked.

-> I think the document, in general, need to take into account a better idea of who the average reader might be. Right now the document seems very squarely aimed at detector-builder types, but I think it needs to be fleshed out with a little more detail on the physics of the day-1 measurements and their relevance to the overall EIC program. In the detector sections, a little more detail on how a detector operates would help those who are not so detector-inclined. I think the right audience is something like the average BNL PAC member, which means it needs to me rather broad be effective.

-> Although it was painful, in sPHENIX we always tried to tie detector performance back to physics requirements in a way that was very explicit (the reader couldn't miss it). I think this was very successful, and something like that might help here.

My more detailed comments follow below.

Regards,
John Lajoie

Executive Summary - it's fine this is blank now, but the collaboration should see the ext of the summary at least once

Section 1 Title - "The Electron-Ion Collider EIC" is redundant, what about just "The Electron-Ion Collider"?

Between Lines 6-7 - It seems to me there is some "connecting tissue" missing here. The first paragraph starts very broadly describing the EIC, I would expect that a second paragraph could expound more on the goals of the complete scientific program at the EIC, and then narrow down to the physics that could be done in the first five years of operation.  As it is right now I don't know what this introductory section is trying to do.

Section 1.1 Title - "the EIC"

page 2 line 15 (and elsewhere in the document) - Table, Figure, Section and Chapter should be capitalized ( I won't list all the rest in what follows)

Table 2 - would it make sense to list the sqrt(s) for each beam energy configuration as well, maybe in parenthesis or as a separate column? I'm supposed to tie Table 1.2 and Figure 1.2 together only lists center of mass energies.

Section 1.2 Title - " Key Early Measurements"? or "Key Day-1 Measurements"?

page 2 line 21 - "...allows one to constrain..."

page 3 line 7.  "... but due to limited coverage at low-x, a large uncertainty remains (see Figure 1.3).

Figure 1.3: caption ".. at the 10 GeV x 250...", I have a real problem with this Figure and I suspect so will many people outside of sPHENIX. Just showing DSSV08 and the ePHENIX projection is misleading as there have been/will be additions since DSSV08.  In particular, in the RHIC Cold QCD Plan (https://arxiv.org/abs/1602.03922) Figure 1-5 shows DSSV 2014 and the anticipated reduction with RHIC 2015 for the running integral of delta-g.   (There is also Figure 3-7 in the RHIC spin plan https://arxiv.org/abs/1501.01220.) I don't think it negates the impact of the EIC to present a more complete picture of what is known/will be known prior to the EIC and it looks better to acknowledge the work in the field properly.

Figure 1.5 - First of all, this figure is too faint and small to see the figures properly. Is this a generic EIC projection or an ePHENIX projection? I believe it is the former, which runs the risk of confusing the reader.  If at all possible we should only show ePHENIX-specific projections in this document. If we show a more generaic projection, but we believe it is representative or ePHENIX then we should label it "a projection compatible with ePHENIX expectations".  Basically, any projection that is shown should be something we believe ePHENIX can do to avoid confusion.

Figure 1.6 - There is a big disconnect between the text in this section and the figure. Explain geometric scaling and what it means that most of what ePHENIX would cover is above the solid red line?

Section 2.1:

page 8 line 6 - "Statement is that..."  If you believe it is try just say "TPC dE/dx resolution ca be recovered...", otherwise remove it from the list

page 8 lines 10-11 - leave a space so it is clear these are separate lists

It would be very interesting to have a rough number (to the nearest $1M) of the total sPHENIX investment that could be re-used as a part of ePHENIX at this point.  It should be straightforward to get this number from the sPHENIX resource loaded plan, and I think it would have a real impact.

page 8 lines 25-26 - The stated goal of the collaboration is to have an instrumented iHCAL as part of sPHENIX.  If you want to go with it as just a frame for this discussion then I wouldn't really mention it as a separate item but lump it into the EMCal extension (it would be a nominal part of the cost).

For completeness, I think it would also be useful to also have a list of new detectors components that would be added to create ePHENIX.

page 9 line 5-6: the ".. and therefore.." clause just doesn't fit in this sentence. Leave it out and the sentence is still fine, or say something like "...as well as to provide wide acceptance for jet reconstruction"

Section 2.2.2 - Hadronic Calorimetry needs to be fleshed out. Christine has asked me to do this and I will get to work on that next, after completing these notes

Section 2.3 - This section needs to be written!

Section 2.4 -

page 13 line 11 - check kinematic coverage

page 13 line 12 - update reference

page 13 lines 17-18 - If the fast TOF is an option, this would presumably be in place of the DIRC (and discussed as such)?

page 13 line 23 - "... taking essentially all of the momentum...."  This can't be true? Or do you make kinematic cuts that biases you towards this?

page 14 line 1 - "...with 6-7 GeV/c..."

Section 2.4.1 - This section launches into a discussion of the DIRC without an introduction to what it is and how it works. Maybe a better Figures 2.4 (and referring to it) would help? I'm not a PID expert so I was left a little confused here.

This section seems to be very specific about the size and makeup of the quartz bars - would these come from the BaBar DIRC? If so, can we say that?

Figure 2.4 seems almost useless to me - it's fuzzy and hard to see, the caption is useless, the LHS tells me nothing about how a DIRC works and I don't know what I am supposed to conclude from the RHS.

page 15 line 22 - looks like two sentences run together here?

page 15 line 29 - "... to not add ..."

Figures 2.5-2.7. - poor resolution, useless captions. I don't think they are actually referenced in the text? If they don't support the text then they should be removed as superfluous.  If they should support the text then they need to be properly integrated.

page 16 lines 5-8 - run-on sentence linked with multiple "which" - rewrite

page 17 line 4 - remove the second "reasonable"

Section 2.5  -

page 18 line 8 - missing reference

page 18 line 9 - confirm numbers

We have been talking about the integration of Roman Pots for some time. I think we need to work with CAD to show a beamline diagram with a likely location for Roman Pots.  We've talked so much about this that without showing some work in this direction I think we open ourselves up to criticism.

page 18 line 18 fix citation

page 18 line 19-20 - work with CAD to get Roman Pot parameters

page 18 lines 21-22 - yes there should be a paragraph on ZDC's

Section 2.6 - this section just needs a good editing pass for English, typos, etc.

page 18 line 24 - remove Jin Huang

page 19 line 3 - "A hardware..."

page 19 line 7 - "...access to all ..."

page 19 line 8 "... to improvements in both..."

page 19 line 10 - "... to design a ..."

page 19 line 12 - "...allows a software..."

page 19 line 20 -  delete "as the one accessed by analysis"

page 19 line 14 "... have a long response time..."

page 19 line 29 collisions

page 19 line 19 - "..inheriting and evolving..."

Figures 2.9 - 2.11 Other than showing that these distributions were studies in simulations, what is the point of these figures? The figures themselves don't communicate anything. Are they necessary?

Figure 2.12 - x-axis labels should be larger.  caption "...which is then converted..."

page 22 line 3 - "...through a high-throughput..."

page 22 lie 14 - "...with modifications to firmware and DAQ software..."

page 23 line 10 - space between J/Psi and mesons

Section 3.1 - Tracking performance

Figure 3.1 - the figure should be larger and more legible. the second sentence in the caption should be deleted.

Throughout this section - consistent use of the GEANT4 macro so that it is in the same font everywhere.

There are many parts of this section that just list REF - proper references should be added.

Figure 3.2 - What does "Detectors are drawn in scale" mean? (sp) cylinder

Figure 3.3 - vertical axis would be better as hits/event. What type of event is this for? DIS?

page 26 line 2 - drop A

page 26 line 10 - what is "-.-" for?

page 26 line 12 - sections

page 26 line 16 - missing figure ref

page 26 lines 23-25 - be consistent and just say "muons"

page 26 line 26 - "large radius"

page 26 line 27 - our best

Table 3.1 - 100% efficiency and 0% noise?? Really?

Figure 3.4 - (and others) be consistent in how you call out parts of figures throughout the document, and don't use all capitals!

What do I learn from the top set of histograms? There is no z-scale? What type of events?

Figures 3.5-3.6 - What am I supposed ot take from these plots? That you can do simulations? Without the vertical axis for hit density those are useless to extract some sort of occupancy or per-event yield. The deviations plots tell me nothing unless you are telling me that this is different than the resolutions in Table 3.1? Reconsider what these plots are for. What type of events?

page 29 line 5 ".. a large improvement in the resolution due to the large extension of the FGEM."

page 29 line 9 - should be Figure 3.7?

Figure 3.8 - I think these plots are useless.  A table of  the fit parameters for the different eta regions would be better?

page 31 line 2 - "Jets are a powerful too in particle physics..."

page 31 line 4  - capitalize Collider, jets->jet

page 31 line 7 space between PYTHIA and eRHIC

page 31 line 16 shows

Figure 3.9 - (E_reco - E_true)/E_true is just E_reco/E_true  - 1 so in the sPHENIX Jet ToG we typically plot E_reco/E_true. I think in general this is less confusing an easier to interpret. What am I supposed to take from the bottom set of plots? The raw energy output of the barrel calorimeters has a JES>1 while the forward calorimeters has a JES<1?  Of course we will calibrate the jet response in the end to bring both closer to one, so I think this plot seems to indicate an "issue" that doesn't exist?

page 32 line 4 - detector noise. What does this mean? What noise was included in the simulations? For sPHENIX calorimeter jet simulations it is typical to have a 100MeV cutoff on the towers to avoid detector noise. In the simulations the detector noise for the CEMC is properly done and matched to test beam, but not so for the HCALs and I'm not sure what is done for the forward calorimeters, but 100MeV should be good in all cases.  If you don't have this cut then the CEMC noise is likely why the JES>1 for the barrel.

In general we do the simulations, and we shouldn't say "likely" but should offer a definitive answer since it is under our control.

page 33 lines 8-13 - I've shown that using the tracking + calorimetry a much better JES and resolution is possible because the tracking resolution is really quite good out to high momentum; this is true even before trying to combine clusters and tracks in a particle flow approach.  It would be good if this statement could tie back to some sort of simply-stated requirements on jet energy resolution. It is a stronger statement to say that the performance meets the physics requirements

page 35 line 1 the photon

page 35 line 15 - missing section reference

page 35 lines 11-19 - so I assume the electron ID is all done by E/p? Is that correct?

page 35 line 26 - missing equation reference

Figure 36 - fraction of charged particles is different than electron purity? Caption should match figure

page 37 line 2 In the forward

page 38 line 2 - missing reference

 

page 38 line 8 missing equation reference

page 38 lines 13 - 17 - I'm confused by this - we can't use a BEAST parametrization when claiming the performance of ePHENIX!  These simulations need to be updated with an ePHENIX parametrization before submission to the laboratory

page 40 line 4 missing figure?

Section 3.3.3 - conclusion? Do you need a new EMCal? Would seem to argue no?

page 40 line 12 - a high resolution

Section 3.4 - maybe some more details of the simulations are needed here? Is what is shown in Figure 3.24 all DIS events?

page 44 line 18 - use pythia macro

page 42 line 2 - missing Chapter and Table reference

page 44 line 27-34 - why this limitation of the smearing package? This seems to not showcase ePHENIX to its best advantage if you can't make use of the overlap (and begs the question why have the overlap at all? ) Can this be addressed?

Figure 3.25 - in the text there is a pseudorapidity cut -2.5<eta<2.5 (covering the majority of pions produced) but the figure doesn't go out to -2.5 it would be nice to have the figure consistent with the text

Section 3.6 -

page 47 line 4 - the exchange

page 47 line 23 Q^2

page 47 lines 21-29 - All the more reason to showcase better integration with CAD and the Roman Pots - is parallel point focusing possible for our beamline? The less we assume and the more we state is possible (in consultation with CAD) the firmer ground we will be on. 

page 50 line 2 to demonstrate

page 50 line 23 Figures

page 27 line 27 use proper LaTex symbol for >~

Conclusion - the collaboration should see a draft of this as well.

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu