[Gdh_lowq2] comments on your ND3 analysis notes

[Xiaochao Zheng]

Hi Krishna:

I finished reading your analysis notes. I have the following comments, divided into two groups. The first type of comments are a little more "substantial" and may be relevant to others involved in the analysis, and some are just for my understanding. The second type are "finicky" details that others can safely ignore.

First type:
a) I thought for the deuteron we used 14ND3?  What's the reason to use 15ND3?  The extra proton can only add to the background of the D measurement.

b) In addition to lattice and XPT, can Stan Brosky's light-front model predictions for any of the moments measured?  I was at his talk last week at the GHP workshop and it looks like his model can calculate many things. (One interesting thing he mentioned was that the whole nucleon spin is from quark OAM in his model.)

c) footnote on page 13: "the pion poroduction" -> should this be "the pion photoproduction"? (Is the threshold different for electroproduction?)

d) line 413 - Is Nt the total number of the target or just the mass-thickness, which is density*thickness? (dimension not right)

e) line 420 E_detector does not look like an "efficiency". Maybe should use "eta_detector"

f) same line, I think you are missing Delta E' which is the detector's momentum acceptance in Eq.(3.1), or maybe Edetector contains it (but see above comment e). Otherwise how do you get the dsigma/dOmegadE'?

g) Section 3.2. I thought EG4 used delayed reporting. This should be included.

h) link 527-531 -> "we could not make our simulation match perfectly with our experimental data. Therefore..." -> This could be particularly alarming because you did not explain why they do not match. Even though you have a solution, you should explain the possible reason of non-matching can be avoided by choosing different cuts, which justify your solution.

i) line 544: Etot/p is about 0.25 for electrons. Why is that? I thought CLAS EC is a total absorption calorimeter which means this ratio should be 1, unless if Etot is defined not in GeV?

same line, pion are below 0.2 -> Is this consistent with what we expect from MIPs?

j) Fig.3.5: What are the two peaks other than the MIP? And why are they there?  And why did they become only one peak at 0.25 in all panels in Fig.3.6? They appear to be exactly the same data.

k) line 574: I thought the noise is not just from "thermal noise". There can be particles hitting the PMT directly and there can be secondary electrons (which you did discuss in a later section).

l) line 996-997: If I remember correctly, the use of tau for theta><pi/4 did not make sense. Is that true?  I think nobody knew why these are used besides that they were in the code used by all previous experiment (???)

m) line 1057 the error in the CC efficiency: I recall we had an extensive discussion on how to evaluate the error on N2/N1 if N2 is a subset of N1, see https://www.jlab.org/Hall-B/secure/eg4/xiaochao/index_pion.html#04092009

I have not found a solid proof in textbooks. So I think it will be useful if you can add an Appendix to prove the formula used. 

n) Eq.(4.3) I don't know why the normalization sigma_tot is on the RHS. The cross section in the simulated N is what you need, right? So it shoudn't be there (otherwise you take th ephysics out).

Even if it should be there, which you have to explain to me why, shouldn't it be sigma_tot-plus/minus?


-------------------------------------------
Second type (that others are welcome to read, but can also safely omit):

1) Throughout the note you sometimes have "D" for the deuteron, such as "g1D" in the title, sometimes "d", such as all symbols in the Results chapter. -> should keep these consistent.

2) Throughout the document, all "sin", "cos", "tan" should be non-italic. In equations these are \sin, not sin, for example.

3) Need to be consistent how variables appear in text, such as x, W, Q2, etc. They should ALL be in math form (such as $W$).

4) line 238: remove "more so in the very low Q2 region" because this paragraph is for real photons. (right?)

5) line 244 "in order to have the : -> "and thus can have" (cause/effect reversed in original text)

6) footnote on page 13: "the pion poroduction" -> "the pion photo production" (since the threshold different for electroproduction?)

7) line 309 - why the latter polarizability is not considered here?  Perhaps should add "because we did not measure the transverse target configuration".

8) line 320 "The first measurement of this quantity" -> not clear -> change to "the first measurement of gamma-0" 

9) page 17 you should add a EG4 CLAS overall figure, such as the EG4inCLAS figure linked at
 https://www.jlab.org/Hall-B/secure/eg4/xiaochao/index_pion.html#07052016

10) line 413 - Is Nt the total number or just the mass-thickness, which is density*thickness?

11) line 498 "The remaining sample..." -> can remove because it is obvious from the cut list given just below.

12) line 540. Is Etot (and everything in this section) in GeV?  If so, should say so. Same for Ein, etc.

13) line 549 "Q2 bin dependent" -> "Q2-dependent"

14) line 551-554: One might question if you can estimate the pion contamination by fitting to the pion peak and look at the tails under the electron cut. Was this done? And what was the result?

15) line 596. I think instead of "the CC plane" you should say "the plane at which the CC PMTs reside as reflected by the CC mirrors."

16) In Fig.3.8 (and others immediately follow), you can add "ofs" and "sig" in the panel refer to \mu and sigma, respectively.

17) line 618 "because the energy is shared between the two" -> "because the Cherenkov photons are shared..."

18) Fig.3.9 caption. The cuts on the last 3 lines are not clearly defined. You can say in more details "If theta<mu-3sigma but PMT=1, or if theta>mu+3sigma but PMT=-1, or if ... but PMT=0."

19) Fig.3.10 there is a small peak at +3ns. I think these are particles hitting PMTs directly (see comment k above). If so, you may want to explain this in the caption (otherwise people will ask).

20) line 633 what is this "electronic background"? First you have thermal noise, which in my opinion should really be just the general "background". Maybe should sjust say "background" here.

21) line 637 the cut at nphe=25 -> the cut nphe>25 (one could misunderstand it as nphe<25)

22) line 645, any reason why pmin=0.2*Ebeam is used? Is it referred to in previous CLAS papers?

23) line 653 I thought you used the empty cell data to determine the z center. If so should add the plot. Otherwise people wonder where does the -100.93 comes from.

24) line 657 reasonably typo, line 658 loose->lose

25) Fig.3.16 COuld it be possible to add the axis labels directly to the figure?  If not, add in the caption "Itor/2250p(vertical axis)" and "thetaDC1(horizontal axis)"

26) Fig.3.17 caption. "some dead wires" -> remove "some"

27) line 731 spin spin?

28) line 733 "the difference of the count differences"?

29) below Eq.(3.3), no indent here 

30) Eq.(3.3) The use of DeltaN is confusing because one may take it as event count. But then these show up as a very small number because of the large arbitrary values of FC. Maybe you should use a different symbol on the LHS of (3.3).

31) Line 743-753. Do we have explanation for the long-term fluctuations? Related to the target, possibly? Should explain and make it clear that it will not affect the final results because of the method described in later sections.

32) line 764 analysis -> the analysis

33) line 766 "no need to use "C"->"c"

34) line 777 you can be consistent and say "EG1-DVCS-TN-004" (as you do below)

35) line 788 "due to various reasons" What reasons?  SHould explain. If unknown, say unknown.

36) line 793. You mentioned Bosted author name on line 778 but no author for TN-002 here.

37) line 808: shoud say each of the four missing components (px,py,xxx)_miss be less than 0.1GeV

38) line 851 what is "targsign"?

39) line 937 "bee"?

40) page 64. You gave all numerical results for the tracking correction but not the numerical results for the momentum correction?

41) Fig.3.26 should explain and show the region used to normalized Carbon to NH3 yield.

42) Fig.3.27 caption "fron"?

43) line 995 "this quantity" (which quantity?) -> "The total effective mass thickness $\tau$ is calculated..."

44) line 999-1001 should explain these are in cm (otherwise I interprete the 0.4, 0.6 as fractional contribution). Also you may want to add the explanation to each line here (such as line 1001: , which means no ND3 traversed by the particle.etc..)

45) line 1002: have you defined z_target_center and z_ave?

46) line 1012-1013: should you add the equation used to re-evaluate the  momentum components?

47) line 1018 "see 2"???

48) I don't see Fig.3.28 referred to in the text (or maybe i missed it)

49) Somewhere in Fig.3.28 caption or end of section 3.5, you should add "As you can see from .... the momentum correction works as expected because ... (the peak of Delta E is now zero...etc)".

50) line 1023-1024: why the quotation marks?

51) Line 1026: Is it really an assumption or is true? It is the real theoretical prediction, right?

52) line 1063: "we find that the functional form is pretty close to..." you meant "the intrinsic efficiency is pretty close to...", right?

Also, I could not derive why the functional form in line 1063 converges to the theoretical prediction on line 1060 (by Taylor expansion). Did you use Taylor expantion to prove these two are the same for certain range of Npe?  Or is line 1063 purely empirical?

53) line 1084 "to discriminate" -> "to identify"

54) line 1102 Fig.3.7.1?  Where is that?

55) line 1122 "less than 1%", do you have a plot to illustrate this?

56) line 1148: "data f the"?

57) line 1152: "in somewhat the same fashion as pion contamination". Sorry, I don't see how these can be done in the same way because positrons behave the same as electrons. Maybe you should explain the method in a few more sentences.

58) line 1190 "cuts events each with a"-> "cuts, events with a"

59) line 1194 "If the event is one of the above two types" - sorry, I can't find the "two types" definition

60) line 1195 "two types following" -> "two types, the following"

61) line 1205 "Delta " -> "Delta [Eq.(3.13)]"

62) line 1213: again need to define the "shoulder" for C/NH3 matching.

63) Eq.(4.2) similar to comment f) above, where does the detector solid angle and E' acceptances come in? Is that in "Acc"? If yes, should explain on line 1263 such as "Acc is the geometric acceptnce of CLAS that includes both solid angle and momentum acceptance"

64) line 1280: experimentalists, not experimenters

65) line 1290: here, should explain that we need AccEff from simulation for el/QE as well

66) line 1294 how do you estimate bg? Maybe add "see section..."?

67) line 1299 "input" -> "inputs"

68) line 1303: "This choice" -> "However, this choice"

69) line 1318 there is an extra space before ","

70) page 88-89: there is section 4.1.1 but not 4.1.2. Maybe just use bold text for "Outlin of the method" rather than starting a subsection

71) Also, this section does not seem to describe the whole procedure. You should add the whole procedure down to how g1 is extracted. 

And following each step descirbed in 4.1.1, you should add "see Section..."

72) line 1398 How is the external corrections handled?  YOu already did the kinematic/momentum correction that accounted for at least some of the energy loss. Somewhere you should explain clearly that this effect is not double-counted.

73) line 1415 "STEG" appears here but is spelled out only on line 1442.

74) line 1435 "(radiated)" does it refer to only "internally radiated"?

75) line 1448 remind people what the 4 variables are in the two 2D maps

76) line 1563 "make make"?

77) Fig.4.4 show or explain the region used for carbon normalization

78) line 1599 "That should be good enough for practical purposes". Why?  Be careful to never make a statement without backing it up.

79) line 1610 "turned of" -> "off"

80) below line 1613: this paragraph is not numbered. Also, I don't see how you can simulate separated two cased for dsigma>0 and dsigma<0. My understanding, from reading your earlier descriptions, is that you simulate separately for different target/beam helicity combinations, so should be helicity(beam)=+1 and -1.  Because, if you simulate for h=+1,-1, then deltasigma could be either positive or negative, right? But then I don't understand why you store dsigma><0 separately not h++1,-1

81) Also, up to here, I don't see how these paragraphs fits into the outline of 4.1.1 (see comment #71 above).

82) two lines below line 1616: "outlined in the introduction" did you mean "in 4.1.1"? - but it's not there (see #71 above). If you meant step 1 in 4.1.1, then that's misleading because that step is how you eventually get g1 from DIS data.

83) line 1617-1618 "since we assume the ... in this region is reliable" should be "since the physics of QE is known (from form factors etc), we expect the simulation in this region is reliable."

Also how is QE calculated?  Should the QE cross section and the related form factor fits be given?

84) line 1632, need to point out the Delta model is quite reliable too.

85) line 1630, you give two reasons for the fall off at small Q2, but no proof to back it up. If the CC efficiency is evalauted well, then it shold not cause the fall off, right?  So you mean the CC evaluation is not good at high p and low Q2?  And why?

Similarly, what simple cross section model?  is it QE model? (see #83 above). Why does it not work at low Q2?

86) line 1637 should you say the SF should be stable, close to each other, AND approximately be 1?

87) below Eq.(4.7) (line 1670), you should also write that 
B=(dn(non-std)-dn(std))/(dA1*F1*(nu^2/(nu^2+Q^2))).

88) Beginning of Chap.5, before eq.(5.1), you need to give an equation that 

thus, g1std+(dn_data-1.0*dn_std)/1.0B - g1_data = g1_std+delta g_1-g1_data, thus =0 [from Eq.(4.8)]

This equation will be the foundation of all systematic evaluations, Eq.(5.1), (5.2), ..., where you vary the factor 1.0

89) line 1721: I suggest putting everything below as section 5.1 "Evaluation of Experimental systematics". Then Section 5.1 becomes 5.2, etc.

90) line above Eq.(5.4): nphe > 2.5?

91) paragraph above Eq.(5.6): "But to simply the sitation, we increased the RADA parameters in ... by 20%...". So, how do you know RADA has the same size effect as RADB?  In other words, what is the justification of not doing RADA and RADB separately at 10%?

(besides convenience, of course)

92) move the upper half of page 119 (definition of choices) to before line 1747.

(particularly true given that you say "After the simulation data for above four cases" on page 119. And the "four cases" are not directly above, but on the previous page.

93) page 120, move defintion of sum2, i, Delta to before line 1793

94) lines 1805 thru 1811: I don't think any of the brackets is necessary here.

95) Ref. 29 on line 1814, priv. comm. with Sebastian, is it necessary to reference it here? Isn't he a coauthor of this note?

96) line 1818: "with with"

97) line 18920 remove "in separate columns (one row is for...)."

98) Fig.5.1 caption: add "Left" at the beginning, and explain at the end "Right: extracted g1 vs...."

same caption, you have "see Sec.5" too many times. Also, these should be 5.1 (or 5.2 if you follow comment #89 above). Use "see Sec 5.1" only once after you list all systematic factors.

99) Eq.(5.13) is not necessary. You can just say Sum2 is in Eq.(5.10), or add a line "which is the same as Eq.(5.10)" (I looked back to see if these are the same as before.)

100) Eq.(5.16) you have k=8,10,11 -> typo?

101) line 1839: "as before" -> "as Eq.(5.10)"

102) line 1841 "linearly"-> "linearly, weighted by statistcis".

103) line 1845, near end: "taking the sqrt of the sum." -> "taking its sqrt."

104) line 1847: The figures -> Figures

105) line 1858 missing period. Also you have been using Figs. not figures

106) line 1873-1874: remove brackets.

107) Throughout Sect.6 you have "extracted from the two different beam energies". If these are the ONLY two energies of EG4 ND3 run, then can remove those.  Otherwise, everything I see this, I ask "where are the other beam energies?"

same for most figure captions in Section 6, line 1890, etc.

108) line 1883: the sign change is also present in the exlcusive results. You could refer to the exclusive paper here.

109) line 1890, even if you have to poitn out the beam energies here, why so many significant digits?  

110) line 1911, I suggest use a separte equation to present delta x, and define it as \Delta x(W)

111) line 1925, use "delta x(W) instead of "Delta x" in the summation. (to show clearly that summing over W bins is integrating over x)

112) line 1946 "well" -> "well with data"

113) throughout Sect 6 you have only "Gamma1" etc in Figure axis. If this is for the final publication, I suggest adding "d" as subscripts in all figure axis labels. 

114) line 1960-1961:  It's not clear what thes "higher order terms" mean or used. Did you mean higher order terms in XPT calculation? What type of higher order? "additional unknown constants" -> can you provide examples "constants such as..."?

115) Fig.6.11 caption: there are at least 3 models in the graph, but only "a xPT prediction" is mentioned in the caption.

116) cpations for Fig.6.12, 6.13, 6.14, 6.15, no need to say "with a ... scale used for Q2". YOu can say "Extracted Itt for the deuteron vs. Q2, compared with...". (People can tell whether it's lin or log scale).

117) line 1982, add "using two beam energies 1.3 and 2.0 GeV after "ND3 target)".

118) line 1984: unit for W is GeV, not squared;

119) 1986 "in the overlapping region". Was EG4 more precise in ALL overlapping region?  If not, say "in the overlapping region below Q2=...".

120) line 1987: "unmeasured lower Q2 region" -> "unmeasured region below Q2=0.5".

121) line 2000: (or cross section) you meant the cross section difference or polarized cross section, right?

122) line 2004: "(up to now)" -> "before EG4" (remove brackets too).

123) line 2018 remove "i.e for"

124) line 2032: add at the end "for all 3 moments"

125) line 2035: remove "and results expected to come very soon"

126) line 2036 "the near future"

127) line 2037 "the free .." -> "free"

128) line 2040: "particularly" 

129) line 2042: "nucleon spin" -> "the nucleon spin"

130) line 2043: "functions" -> 'functions and their moments"

131) line 2049: "the future".






----- Original Message -----
From: "Elena Long" <ellie at jlab.org>
To: "gdh lowq2" <gdh_lowq2 at jlab.org>
Sent: Monday, January 30, 2017 9:53:17 AM
Subject: [Gdh_lowq2] No EG4 Meeting This Week

Good morning,

This is a reminder that we won't be having an EG4 meeting this week.

As Alexandre already noted, please use this saved time to finish reading 
the second version of the deuteron analysis note, which should be send 
in a few weeks to the review committee. Krishna posted it at 
https://www.jlab.org/Hall-B//secure/eg4/adhikari/Analysis/Pass2/AnaNote/PDFs/analysisNoteV2.pdf

Take care,
Ellie

-- 
Elena Long, Ph.D.
Post Doctoral Research Associate
University of New Hampshire
ellie at jlab.org
elena.long at unh.edu
(603) 862-5312
http://nuclear.unh.edu/~elong

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