GEM TDR

Overall Comments:

Currently I have read only the chapters 1 and 6 and my comments will be constraint to this part. The case for strengthening the muon triggering and reconstruction using GE1/1 in this region is a good one, although with the current results (absence of section 6.4) it’s very difficult to judge the cost benefit ratio.

-Valid for all pictures (in chapter 1 & 6): When printing the document in black and white it’s impossible to follow the text since the text is referring to the different colours.

KH: what is the general policy for the TDR? For the trigger rate plot, the mentioning of colors can be dropped from the text (DONE). I would have left it in the fig. caption but noticed that it had disappeared from other captions. Therefore I removed it from the trigger rate plot as well.

-In many cases statements about results are made without a reference. Can be good to add them.

Anna: please note that, since the main physics gains come from the fact that we are able to control the rate in the forward region and keep low trigger threshold (with high trigger efficiency) in all pseudo-rapidity range, we have decided to include the physics results in the following sections (NO SECTION 6.4 ANYMORE):

6.2.2 Muon trigger performance in Phase 1

6.2.3 HL-LHC trigger performance

For phase 1, the main argument, as we said, is H->tau tau->mu+tau+Met, where it would be good to keep low PT, inclusive, single muon trigger, since the pt of the muon is very loose. In L1 trigger TDR the offline threshold is set to 22 GeV, which correspond to the 95% of L1 trigger efficiency plateau. So we considered three different thresholds around that value (15, 20, 25 GeV) and we have demonstrated that we are able to gain 35% in final selection efficiency for each 5 GeV of reduction in pt threshold.

For phase 2, the main argument is to keep high sensitivity of the standalone muon trigger to signatures with displaced leptons where L1 track trigger cannot help. We thought that putting these results after the reconstruction, section 6.3, would have interrupted the flow of the argument.

We thought that putting these results after the reconstruction, section 6.3, would have interrupted the flow of the argument.

Anna: please also check, for expected background and signal yield at 13 TeV, comparing to 8 TeV results, the following strategy studies for Htautau at 13 TeV https://indico.cern.ch/event/363307/session/20/contribution/22/material/slides/0.pdf

Specific comments:

-Section 1.1: In this section sometime you refer to the HL-LHC. I found this a bit confusing since here you would like to make the case of the important of GE1/1 to be anticipated into LS2.

KH: there is indeed some confusion. I changed in particular L163. This is an important modification, CHECK. Also changed eta range to 1.5-2.2 which should be the "official" GE1/1 numbers. Now it reads:

The GE1/1 installation is part of the general plan, described in Chapter~4 of the CMS Phase 2 Technical Proposal\cite{CMS-PHASE2-TP}, to improve the forward region $1.5<|\eta|<2.2$ of CMS muon detection so as to maintain high triggering and reconstruction performance in the face of HL-LHC conditions. Besides GE1/1 (foreseen installation in LS2), this plan includes installation of a second station of GEM detectors (GE2/1), and third (RE3/1) and fourth (RE4/1) stations of improved RPC (iRPC) detectors during LS3.

In addition, in this version is little bit weak the part related to the physics improvements. May be will become stronger as soon you provided the updated version with section 6.4.

see results in 6.2.2

-Section 1.2:

-L257: you refer to analog and binary readout. But the results sounds all related to binary readout. May be it’s something to be clarified and eventually you would like to insert reference to these results.

KH: I think diff VFATs were tested. Anyway, we don't compare the performance analog-binary though. Dropped this sentence.

MH: In Ch.2 we actually do show plenty of results from BOTH binary and analog readout. SUGGEST TO RESTORE THE SENTENCE. Otherwise the following sentence does not make sense (can't measure detector response uniformity with binary readout)!

-L265 onward: there are several acronyms not defined, like GEB, GBT and so on. Many of these are defined later like in Section 1.3 starting from line L312. I suggest a re-edit of these 2 sections.

Done for GBT and GEB. VFAT, MP7 and AMC are not defined but I think it is not necessary (name).

GLIB not defined yet.

CHAPTER 1 finished here

-L1805: large datasets. What you meant?
we have removed

-L1818: Fig 6.1 (right) is this for PU140 or PU50. The text sounds refer to PU50 while the picture mention PU140. Since here you would like to motivate GE1/1 after LS2 may be better to have PU50. Or I am missing something?
. It is for PU140. GE11 it is a Phase2 project with an early installation in Phase1 (when we can gain a lot already). We will show plots both for the post-LS2-scenario and LS3 scenario, to make it clear that GE1/1 will not stop operating after LS-3.

-Section 6.1.1: May be this section can be removed since it’s unclear why you are including these details. If instead there is a specific reason need to be clarified.
we have removed

-Section 6.1.2: While I can understand from the text why GEANT is NOT used to study the background, need to be clarified when you use FLUKA and when GARFIELD. Finally you may merge section 6.1.2 and 6.1.2.1. In this way you will avoid several repetition that I currently see.
RH: The results from the standalone simulation with GARFIELD have been used as an additional crosscheck for the individual detector characteristics as cluster size, efficiency and minimum amount of ionization. They are not used directly for the evaluation of the background. In order to avoid an ambiguities the related sentences are removed in the new text version.

-L1931. When you mention validity of FLUKA with Run1 data. Can be good to add a reference.
Anna: done

-Figure 6.2 (left and Right) in both cases you refer to HL-LHC. Since we are asking to include GE1/1 after LS2. It’s better to put these results for 2*10^34 cm^-2s^-1.
Anna: The important point we make there is that rates that GE1/1 will see even at highest luminosity are well within the margin of safe operation for GE1/1. We show the post-LS3 plot to make it clear that GE1/1 will not stop operating after LS-3. (A.S.)

-L1957: Are these studies done using a standalone geant 4 version. If this is the case, may be should be specified.
AM: Done

-Section 6.1.2.2 In these section there are some repetition with the rest of the sub-section 6.1.2. Can be good to have an overall re-editing to simplify the concept.
We did a significant cleanup of these sections to avoid repetitions. (A.S.)

-L2015: put a reference to the test beam results.
RH: Done

-L2057: May be good to put a value when you menation from the margin of safe and reliable operation for the GEM-based detectors.
Anna: This has ben described in detail in Chapter 2 and we have added a reference to that

-L2069: These statements are repeated several times along the document but we need to make sure that we have the results. I suspect that will be in section 6.4 that is currently missing. So I am waiting for that.
We believe H->tau tau results address this. (See section 6.2.2) We have to repeat it a few times as this is the key element of motivation for GE1/1 (A.S.)

-Section 6.2.2 This section sounds little bit generic. Do we have some specific study? May be some of the study that you are mentioning should be done using CMSSW or at least Delphes in order to demonstrate the real benefit.
In section 6.2.2 results for Htautau are provided at the end of the full simulation (Anna.)

-Section 6.2.3 I am not sure that this section should be included since we are requesting to include the GE1/1 during phase 1. In addition this section is making the comparison between the general phase 2 muon upgrade and tracker upgrade and not just GE1/1.
The reason for this discussion is to ensure that people understand that GE1/1 will not become useless just a few years after its installation. This is a reasonable question to ask and it has been persistently coming in each and every review we went through until today. It is more than likely that this question will come again and we want to have a firm answer to that in the TDR (A.S.)

-Figure 6.13 from the text sounds like that should be 3 curves while I see only 2. So may be need to be clarified.
Archie: Caption corrected

-Section 6.3.3 in figure 6.14 (left & right) you refer to 50 and 140 PU with Gem 2019 configuration. Why? Which is the main message that you would like to pass throght?
Anna: Since GE11 will operate both in postLS2 and HL-LHC we would like to show that the new detector is useful in different operation conditions. In the plots that both at the low and high Pile-up 50 and 140, same behaviour is seen: efficiency is improved with GE11 and fake rate is not increased

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-- MichaelTytgat - 2014-12-17