I added the line numbers.

Chapter 1: Introduction

Link to the intro chapter


Jessop Comment

The intro lacks any context for the LHC and CMS. I think the first paragraph should describe what the LHC is and it significance in particle physics - i.e a discovery machine at the highest energies yet achieved, then some words about CMS - i.e its perhaps the most technologically advanced detector ever so it deserves a few words. Then something about how this thesis is one of the first measurements to be made. I would try to mention that it particularly uses the ECAL which is a detector that you helped build, commission and operate.

The first paragraph you have now should become the second paragraph. Again theres no context for what QCD actually is and why it is so important to understand it - i.e its the theory that underlies our ideas of how quarks and gluons interect so unless we have a good idea that it works at 7 TeV we can not do any other physics. Also its a background to absolutely every search for new physics so again we cannot discover anything until we are pretty sure that we can model the backgrounds reasonably well. Its a lot more than "useful early input" - its essential ! In your remarks about the usefullness of photon processes you should also mention that its vital to set the jet energy scale which is quite critical for evertything else

Again Higgs and SUSY are mentioned without describing qualitatively what they are. You dont need to give a full on explanation but a few sentences of context would help.

Paragraph 2 and 3 are a bit too technical. I think the first challenge you faced was making the detector work properly so you should have a few sentences on that. The details about the isolation versus conversion method should come in the analysis section. The discussion of previous measurements should come later too.



I tried reversing the order of the paragraph p.2.l.12-24, let me know if you think it reads better this way. TedKolberg 14-Jul-2011 - 11:03

"This thesis exploits etc. etc " deos not sound terribly nice. I would invert the order (and way). I would say first what the method is and it would follow well what said in the previous paragraph. While introducting the method you can refer to the what done before by CDF. Then you can say that in CMS this procedure is particularly effective because of the quite massive tracker, the large conversion probability etc. etc. hence a statistical power not negligible leading to a competitive result.

NancyMarinelli 13-Jul-2011 - 18:22

Chapter 2: Theory and previous measurements

Link to theory and previous measurements chapter


Jessop Comment

The first paragraph describes QCD consequences without mentioning some of the basic ideas. That is that it is an SU(3) non-Abelian gauge field theory. You should describe what SU(3) refers to (color charge symmetry) , that the fundamental feature is that the gluons carry color (non-Abelian) which leads to the features you describe and that it is renormalizable (gauge field) and what renormalizable means. You also need to mention that there are 6 flavors of quark and eight gluons

In the lagrangian the notation does not make explicit the sums over flavors and colors. You need a bit more explanation of the Lagrangian - i.e what each of the terms means. You dont described what the running of the coupling constant means and why it occurs nor what the renormalization group is. You dont need detailed expositions but a few sentences to describe what these things are qualitatively.

P6 lines 5 to 9. I am not really happy with this explanation of the division between perturbative and non-perturbative and the idea that the higher order terms are always small (they are not always). I think the point is that generally you cant solve the lagrangian analytically but that in many cases (high and low energy) you can factor the interaction into short and long distance components and use perturbation theory to get at the short distance component. For LHC the quarks are free so theres no long distance component but for say low energy B mesons you can still do this factorization and use perturbation theory but you have to use some other technique for the long distance component such as lattice QCD.

P8 line 2 Before you launch into a description of PDF's I think you need to describe qualitatively the structure of the proton and how it changes at different energies. This provides context for the PDF discussion that follows

P8 line 8 "Various techniques .." is too vague. Give short overview of the techniques. PDF's are quite important to what we do. Also describe at some point (maybe later) you need to mention what PDF's we use at CMS now and how they are being modified by measurements such as yours. Likewise for fragmentation functions.

P 13 line 18. I'd like to see a paragraph about JETPHOX and why we think its a good MC. Its important not to just treat MC as a black box but to consider their validity and limitations.

= I removed some of the historical discussion and replaced it with explicit definitions and examples for the distinction between perturbative and non-perturbative effects.

As for your point (3) below, I tried to solve confusion between "direct" and "prompt" by doing the following

-- Used "prompt" e.g. in the chapter title because it is the most accurate ("prompt" = "not from decays")

-- Removed any reference to "direct" or "fragmentation" except when specifically discussing the separation of the calculation into the "direct" and "fragmentation" part. Let's avoid using these terms in any other context because the distinction is not physical.

NOTE: I am trying not to get biased by personal matter of taste

1) Dear Ted, I went once through this chapter. My first impression was that you tried to write down in few pages what normally would take a book. As a result Sec 2.1 gives little and fragmented information which takes space but does not give finite infromation. I would rather be more factual, drop the attempt of being a historian and enter head on in the description of the direct photon production as described by the QCD. You need to give for granted that something is known and write as better as you can following on that assumption. I would say how a QCD lagrangian looks like, define what perturbative means and what the implications are. Then dive into the single photon cross section applied to pp interaction without naming the LHC because we have no idea at this point what the LHC is.

2) In any case the beginning of Sec 2.1 would better be written as: QCD is a quantum field theory, developed within the framework of the Standard Model, which describes the strong interactions intervening between quarks and gluons, the basic constituents of the hadronic matter. In contrast to other theories (Example ??), QCD is remarkable because it describes well a complex system which exhibits very different properties depending on the energy regime considered.

3) you have to choose between direct, prompt and isolated photon, Direct, as opposed to fragmentation is much better but needs to be defined before starting telling the tale. In this light the title of Sec. 2.2 would become Direct photon production In this chapter you also mix direct and prompt with isolated. The isolation concept needs to be defined well and I am happy if it is done in this chapter at the very beginning so that it can be reprised later when from the theory one moves to the experimental view of it,

4) I wrote down on my copy more detailed comments but the major point is that the organization is not optimal so I decided not to write down the detailed comments.

5) in Sec.2.3 in the first few lines jets enter the game, while talking about photons, without any explanation,

6) Always Sec, 2.3. You wanted to give the history of the experimental history. The tale should stop at CDF (with due references everywhere). ATLAS and LHC are the present , not the history, and they should be named later when you enter in the discussion of your own analysis. Also, at this point, we know nothing about the LHC (will be talked about in the next chapter) and about ATLAS.

| NancyMarinelli | 13-Jul

Chapter 3: LHC accelerator and CMS detector

Link to the LHC/CMS chapter

I added two paragraphs about CMSSW at the end of this section so it does not come out of nowhere later.



Chapter is very good. Only thing to add is some discussion of the run plan - i.e some idea of what amount of data we plan to take and when Jessop 21Jul-2011

I made several major additions in response to Nancy

-- added some paragraph of overview on the LHC physics program, this motivates the sections on design of the LHC and CMS

-- expanded greatly the LHC design discussion, explicitly calling out the features which allow it to reach such high energies and luminosity

-- other small changes to clarify the text, including a picture of the coordinate system next to the detector


0) I believe that in the introduction, when you say what each chapter is devoted to, you should inform the reader that in chapter 3 an overall description is given about the LHC and the CMS detector. Fot the latter special emphays is given to the sub-detectors mostly used in the analysis, the ECAL and the Tracker.

1) Drop the first 3 lines. Those are for later.

2) Collision at the TeV scale is unfair. Tevatron is already at TeV scale. LHC design energy is 14 TeV center of mass enery, now running at half it's design energy which is anyway the largest ever reached. You say all this much later in pag3. 20. All that part should be moved right at the beginning.

3) Protons destined to LHC etc.etc. would sound better as "The acceleration chain of proton beams begins in the Linac2 etc etc. 50 MeV energy. Protons are then injected ...... rings where they are accelerated to 1.4 GeV and accumulated into so-called "bunches". At this stage the (nearly) final transverse and longitudinal size of the bunches is already achieved,

3_1 ) As you anticipated in your warning, I think that the text you resrved to the LHC is really too short. You could spend some text describing the main features/parameters of the machine, what a marvel it is. You should also spend more to describe the definition of the luminosity and why we need a machine running at full blast.

4) Sec. 3.2 The physics program was never really explained. You spoke about the long waited Higgs but there is much more than that. You could spend a few more words about that. "CMS was designed to cover the largest possible range of physics accessible at the LHC" should replace "...for analyzing the particles produced in LHC"

In order to achieve this CMS was designed to meet stringent requirements as: - list

5) I'd replace " good electron and photon energy resolution " with " excellent electron and photon energy resolution "

6) I am not sure that the committee who will examine you will appreciate the south and west direction you give or the name of the Jura mountains wink Would be much better to stick a schematic drawing of CMS with the reference axis showing the orientation together with the magnetig field direction and the angles you decribe in the text.

-- NancyMarinelli - 14-Jul-2011

Following comments are still based to your first version.

7) Sec. 3.2.2 about the Tracker I find it a little disorganized. I get the point that you want to give an overall introduction about the entire system but the result is that there are repetitions (e.g. you repeat twice in 3.2.2 and the size of the pixel cells) and I find it quite cahotic and with no essential content. The 3.2.2 can be reduced to few lines devoted to very schematically describe what the Tracker is made of. First of all in the title do not call it Inner Tracking detector, otherwise one expects to find an outer tracking detector. Just call it Tracking detector or Tracking system. Tell in a more precise way what CMS expects from that device: pt reolution, vertex resolution, hit position resolution in numbers. There are none, even in the sub-sections. Lots of space is spent in describing the hardware but before getting there a few, coincise and precise statements about the performance are needed. Then, you go in the subdivision of the detector saying that it is composed of a Pixel Detector (leave the details to the corresponding sub-section) and a Silicon Strip Tracker detector. The latter is further subdivided into bla bla. You can tell that Tracker overall corresponds to N million channels, N square meters silicon etc. etc. hence the amounf of material etc. etc. In fig3.4 replace with The layout of the CMS Pixel + Silicon Strip tracking system.

8) Sec., page 29 When describing the modules or the type of sensonrs, the most important thing is that you talk about the single sided and the double sided and, even if you do not say where the double sided (3D points) are located, at least say how many 3D points we have along a track. That's what more relevant in the discussion.

9) Half of page 31 spent for cooling ..... it's more than a bit over the top. Cut all those details and concerntrate on the first part regarding what influences more the performance.

10) What is written in the ECAL part is written in a reasonable way. BUT there are lots of details, I believe too many, about the hardware again. But there is not a word about what the poor thing is able (or supposed to be) to do, which is the thing on which you need to put the emphasys. You speak of high resolution. How much ?? THAT's the reason why all what say below was chosen. You're writing a thesis about physics, not about detector. So you need to balance well.

page 32 first line " The CMS Electromagnetic Calorimeter (ECAL) ....etc et.c

6th line: " good resolution " --> high resolution and radiation hardness

page 34, immediately below Fig3.7: during running --> during data taking

page 34, section

line 3. ... a cutaway...

Two lines below: I would write " Each crystal is slightly tapered in an eta-dependent fashion so to be arranged in a quasi-projective etc etc.

Page 35, first line. This off-pointing configuration NB In the TDR or you could ask around, there must be a drawing showing the tilt and how the shower hits the csrystals. Would be nice to stick it in here.

Page 35: 5th line. " .... the crystal size is similar to the Moliere radius ( ) at the front face, broadening to 26 mm at the back " I would say " " .... the crystal size at the front face is similar to the Moliere radius ( ), broadening to 26 mm at the read end "

Off-pointing and not offpointing everywhere.

Page 36: Physics operation would better be data taking.

Page 36, 37. I am not really sure you wish to quote the company names who built the various bits.

Page 37 towrds the end: " The VPT sensitivity can change etc. etc. " and following reads very badly. We can keep note and trying to rephrase it later.

11) Preshower. 6th line. " .... adds additional position resolution etc. etc. ". Vague sentence which adds up to the total lack of knowledge of what the ECAL resolution would be ....

12) HCAL

-- Hcal is designed to complement the ECAl in the measurement of hadronic jets ..... sounds more than a bit funny. HCAL IS the primary dector for jet reconstruction. Ecal gets only the EM component which is by far smaller. Please rephrase.

13) Also for HCAL a few words about the basic priniciples on which the detector is based, and perfromance is mandatory. The reader would be much happier to see a nice, down to earth explanation of why we need a brass calorimeter, what that does to hadrons and what we measure. You would want to show that you understand what is the detection mechanism. Ditto, of course, for all other detectors. Whoever will read your thesis, if interested in the very technical details, can get the ECAL or HCAL TDR and read about them. In the thesis you have to show yourslef and tell people that you know how the detector works.

14) Muon detector: As nowhere else you mention some physics. But out of the blue you speak about more accurate invariant mass than with electrons. You speak about the challenge of muon identification. Why is challanging ? The non HEP member of your committee does not have the least clue.

15) In this chapter I found "acheived" instead of " achieved"

16) DAQ and HLT. The Filter Farm does have NOTHING to do with offline-quality data processing (page 49) The title seems to include HLT but there is not a word about those. If there are issues of length, I would sacrifice a page (or more) of the previous sections to speak about HLT which, as you know, are something CMS cannot live without.

Chapter 4: Photon reconstruction and selection

Link to the photon reconstruction and selection chapter

Split the samples off into their own chapter.

-- NancyMarinelli - 3-Aug-2011

Introduction: The statement " since the conversion electrons can lose energy by bremsstrahlung in the strong magnetic field ...etc. etc." is misleading/wrong. The electrons lose bremsstrahlung energy by interaction with matter no matter what. The presence of a strong magnetif field leads to a large bending of the charged particles. As electrons bend in the magnetic field and radiates the lead to an energy deposit in the ecal largely extended in phy. The same comment applies to what you wrote again in a msielading way in sec. 5.1. Please fix it.

Sec. 5.4.1:

Page 65, Line 11. Not sure what you mean by "relatively constant". Also, Fig. 5.2 might well be a plot done by you for the interesting range of energies.

Page 65 Line 13: .... is based on the electron track reconstruction and on the distinctive etc. etc.

Page 66, line 1 .. secondary vertices from massive particle decaying in flight ... etc. etc.

Sec. 5.4.2. Besides many repetitions of the same concepts in the space of 3 pages, I see again here the wrong statement I commented already before. Lines 6,7 " The CMS magnetic field causes the e+e- tracks to bend along the phi direction and also causes the electrons tro radiate energy as bremmstralung before they reach ECAL. a) I would try to seriously reorganize things not to repeat 3 times the same concept. b) fix this because it might be embarassing.

I also stuck the data/MC samples in here, maybe it's awkward like this...

Chapter 5: Data and simulation samples

Data and simulation samples

I do not think its necessary to catalog the names of the data sets and different triggers. It is sufficient to note any significant changes in the text and just qulaitative note how you deal with them.

-Main.ColinJessop - 27-Jul-2011

-- NancyMarinelli - 20-Jul-2011

Details about the version of the software used are really irrelevant in the thesis. What might need a few words, (need to find the right place where to put it) is a brief description of what the reconstruction sofware does. From raw to reco. Without spending too much time on it though.

-- NancyMarinelli - 26-Jul-2011

Table 4.1. The samples names EG/Run2010A etc etc are of little meaning for the external reader. What EG or Photon means ? I know that you gave details about triger conditions in a previous chapter, but either you repeat here what the triger conditions where of if the sample was skiimed aned how or you re-work things so that you put everything in this section and make it coherent. Certainly the Dec22Rereco name is of little info for a non CMS person.

Tables 4.2, 4.3 Later on, when things are most stable, try to paginate better so that Table 4.1 appears in the text prefererably after you have given already a good part of the Pythia descriptionso that the Z2 tune mentioned in the sample names assume a meaning, Overall, as for data,I would replace the CMS string names for the sample with something more meaningful for a an external reader.

Line 21, page 68.You should improve the introduction of the underlying event. While talking about the generator you start talking about measurements perfromed in data and it sounds odd. I would do something like " behaviour observed experimentally in LHC pp coliisions and the presence of underlying events. Since the majority of the products of the hard interaction falls etc. etc. and give here the additional details.

At the very beginning of this chapter would be good to say that a simulated event is the result of different steps: physics event generation, simulation of the particle interaction with matter and detector repsonse, digitization of the response and finally reconstruction So the reader has already in mind what is going to be described.

Chapter 6: Signal efficiency and background subtraction

Link to Chapter 6

Chapter 7: Systematic uncertainties

Link to Chapter 7

Chapter 8: Results and conclusion

Link to Chapter 8

-- TedKolberg - 11-Jul-2011

Edit | Attach | Watch | Print version | History: r27 < r26 < r25 < r24 < r23 | Backlinks | Raw View | WYSIWYG | More topic actions
Topic revision: r27 - 2011-08-04 - NancyMarinelli
    • Cern Search Icon Cern Search
    • TWiki Search Icon TWiki Search
    • Google Search Icon Google Search

    Main All webs login

This site is powered by the TWiki collaboration platform Powered by PerlCopyright & 2008-2019 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding TWiki? Send feedback