CEPC Physics and detector regular meeting
Wednesday, July 18, 2018 from 15:00 to 17:10 (Asia/Shanghai)
at IHEP ( A415 )

Attending: Joao, Huirong Qi, Zhaoru Zhang, Jianbei, Haijun, Mingrui Zhao, Meng Wang,  Jianming Qian, Zhijun Liang, Hongbo Zhu

1. Introduction from Joao
1) Next CDR editorial meetings:
• Tomorrow, Thursday 9 pm —> Overview of physics and performance chapters
• Monday, 2 pm —> Muon detector and magnet discussion
• Wed, 3 pm —> Plenary meeting at usual meeting time
• Thu 26, 9 pm —> Update on physics chapter discussion
2) Joao ask people to provide questions regarding any issues you see with ANY of the sections. We should not wait for external reviewers to point out to us problems that we can solve ourselves.
3) Each detector group should carefully examine the corresponding performance section for any issues, which need to make sure we describe the same detector everywhere. Detector groups please provide feedback to Joao that this has been done — Deadline Monday 23
4) Joao go through the structure of CDR for Jianming, then Jianming pointed out several comments:
    •    Jianming suggested to change the chapter 10 “Physics performance ” to “combined detector performance”
    •    For Vertex detector chapter, there are too many sub-sections, it is better to merge some of them, for example, chapter 4.1.7 critical D&D and 4.1.8 Future R&D can be merged.
    •    For physics chapter, it was suggested to add a sub-section for flavor physics. Joao agrees but it is too late to have it in the benchmark chapter. This will go better in the physics case introductory chapter. Joao will contact Liantao and possible Lars Eklund regarding this.   

2. TPC status from Huirong
1) Huirong said that there are 3 person helping with editing. Huirong will revise and re-write the chapter based on the comments. Wang Zixu, a graduate student from Dutch Univerisy, will help to revise the sentences. Deng Zhi will revise the electronic part.
2) For TPC section, Charlie’s comments are mainly for the sentences improvement. Huirong said they will try to implement the comments by Friday, and have a completed new version on Monday (see below).
3) For the comments regarding the operation at high luminosity and the comparison with Alice TPC, the new performance tests will be updated by Monday.
4) Joao asked about the performance for TPC in 2T, Huirong said that with 2T, the geometry may be enlarged for 2 times, or the resolution will be worse than 30%. This results is coming from the formula 4.4. People discussed whether we should add this statement in CDR. Huirong prefers not to add any statement regarding operation of the TPC at 2 Tesla in the CDR since this is probably not a feasible solution for 2 Tesla -- the TPC is the baseline for a 3 Tesla detector.

3. Go through the Charlie’s comments for silicon tracker with Meng Wang
1) For the geometry definition, we should not directly point out the parameter without any explanation. We could say that because we want to achieve a certain resolution, we need the new geometry from physics requirement mentioned in chapter 3. In this way, the chapter 3 should have a unified the physics requirement for each sub-detector.
2) “The CPS provides better single-point spatial resolution and solves the problem of multiple hits.” —>  "...resolution and reduces the ambiguitity caused by multiple hits in a single strip".

3) Charlie marked the statement for air-cooling without any comments, Meng will ask him if he has a specific comments for this part.
4) For chapter 4.2.6, change the title to silicon tracker performance, to make it clear this only refers to that part of the track, i.e. it does not include the TPC.
5) For figure 4.8-4.10, change the name of “purepixel” to a more suitable name, also make font size large. If figures available in PDF, this should be feasible without having to remake the plots.  If it at all not possible, add a note for “purepixel” in caption. 

6) We also had a long discussion about the essence of this plots. Zhijun notice these don't seem to be for long-pixel sensors, but rather small square pixels. He asked for the pixel dimensions to be provided. Wang Meng replied that the study only used the resolution, not a real strip size, so that is not avaible. We can derive the size of the pixels from the resolutions. Joao commented that the small resolutions indicate spacing between strips, or pixel sizes of the order of 34 micron, at most. Such small pixels would not be feasible due to high cost. We need to discuss further to decide if such plots could be added to the CDR.

4. Calorimeter status from Haijun
1) Haijun will go through Charlie’s comments for calorimeter by this weekend. The deadline for calorimeter chapter is next week on Tuesday. We will discuss the calorimeter chapters again on Wednesday and by then it has to be in very good shape. Text should follow the direction of the DR chapter which had very few comments.
2) Don’t mention the ILD, CEPC-v1 and pre-CDR, for example, we should say the number of layer is the optimized geometry.
3) There are too many details for this chapter, try to shorten some text. We can introduce the baseline in details and other options can be shorten.
4) The detector performance from simulation should be coincident with detector chapter, talk with Manqi to unify the results, for example the photon resolution with 3% need to be accepted by detector people.