[Clas_cascades] Comments to Sigma*- analysis note

[Haiyun Lu]

On 08/14/2011 05:58 PM, Elton Smith wrote:
> Hi Haiyun,
>
> I have just now had time to take a look at your analysis note. 
> Generally, it is well organized and readable. Here are my comments:
>
> General:
> 1. It would be nice if you could add readable legends to your 
> postage-size plots. Otherwise indicate direction (left to right, top 
> to bottom) and also the bin widths, e.g. 0.25 GeV energy bins in the 
> caption
> 2. You should add a section in the introduction to define your 
> variables. For example you use t (=(p_gamma - p_K+)^2?), but never 
> define it. The same can be said for t', etc. Sometimes variables can 
> be used differently in various contexts, so you should not assume that 
> a particular variable is unambigious. It can also help make the text 
> cleaner, if you can refer to specific variables.
> 3. I suggest you move Section 7.1 and 7.2 into the introduction, 
> perhaps breaking 1.1 into two subsections, one on Sigma*- and one on 
> Sigma*0. First, this makes sense, because the introduction discusses 
> previous experiments and the theoretical context. But also, it clearly 
> separates the other experiment from your data. At the moment Figs 62, 
> 63 and 64 could easily be assumed to be your data, unless one reads 
> the text carefully.
> 4. Generally, the reference section is very meager. I have suggestions 
> below where references are needed.
>
I agree on all of them and I will do the modification.
> Specifics:
> p. 5 middle last paragraph, after two categories:
> Suggestion: One group comprises particles listed in the PDG and the 
> other group includes quark-model predictions for "missing states," 
> which have note yet been observed experimentally.
> The PDG should have a reference to the particular paper you used. For 
> example, some properties change from volume to volume, so you should 
> have the specific reference.
>
will do.
> p.6 event selection
> It is good practice to have an appendix with all the precise run 
> numbers you use (instead of giving instructions for how to obtain the 
> golden runs. Five years from now, these might not be available. It can 
> also be divided into before and after Christmas.
>
will do.
> p, 13. My understanding is that you choose the pi-,p combination with 
> the mass closest to the central Lambda mass. Does this affect your 
> final answer? Can you estimate the systematic error induced by this 
> selection?
>
I don't think this affect my result. The reason is that I didn't extract 
anything from this combination. This combination is only for selecting 
events. After that, the invariant mass of proton and both pi- is used to 
extract the yield.
> p. 16 Tagger correction
> You should reference Paul's thesis.
>
will do.
> p. 21 Section 3.6
> References to CALDB and GPP?
>
will do.
> p. 21 Section 3.7, last sentence. You say that the 0.45 GeV cut is 
> generated. Is this Monte Carlo, data or both? Is the generated 
> distribution similar to the measured one? I don't quite understand why 
> the cut is 0.45 and not 0.25 or higher?/
>
Both. The simulated distribution is similar to the measured one. The 
momentum spectrum is the shape that rises first to peak and then drop. 
If the cut is applied on the peak, that's too much. If the cut is before 
the rising, that's too little. The idea is to apply the cut on the 
inflection point of the rising edge. I will put a section studying the 
effect of this cut.
> p. 22, 3.8 last sentence, clarification:
> ... process, we require the MM to be less than 0.4 GeV.
>
will do.  "the missing momentum to be less than"
> p. 24.
> You make a cut on the K* events. I did not see any discussion on how 
> this affects your final results. Is there a systematic associated with 
> it?
You are right. I did the study and I will put a section on it.
>
> p 25. 4.1
> What event generator did you use? You should also write down all the 
> parameters (or the critical ones) that go into the generator. Define 
> you t variable
> In this section you should also state that you use a t-slope of 2 GeV-2
>
will do.
> p. 27. 4.2
> Again in GPP it is useful to specify the resolution parameters used 
> for tof and DC detectors.
>
will do.
> p. 27. Trigger simulation
> Did you look into the correction for Lambda's decaying outside the 
> start counter? We added a correction in the pentaquark paper (I 
> believe the estimate was 5%?) This was necessary in our case because 
> we required 4 tracks with ST hits.
>
I thought about it and I don't think it's needed in my case. The reason 
is that I normalized the trigger efficiency to the prescale 
factor-corrected rate with trigger bit 5. Even Lambda decays outside the 
start counter, the K+ and pi- produced via strong interaction could make 
the trigger.
> p. 27, 4.4 , first line
> ... can be found in Ref. [1].
>
will do
> third line suggestion
> photons, which are not necessarily selected by the trigger, to 
> calculate...
>
will do
> p. 29, second line
> ...system, even though all T-counters are on.
>
will do
> p 31 4.6
> Trigger efficiency correction section could use clarification.
> first sentence:
> ...discrepancy in the observed yields of various EG3 run periods.
> 4th sentence
> studied the pentaquark [needs reference].
> last paragraph
> You need to define your sample. Graphs say 4-track events. Are they 
> the same sample as your Sigma*-? Is it a less restrictive sample? Are 
> they a Lambda sample with two additional tracks?
>
will do.
They are the same sample as Sigma*- passing Lambda selection. No other 
cuts and not yield extracted.
> On Fig 36 and 37, I don't see the "discrepancy" near the 60th run. Do 
> you mean discontinuity?
yes, will do that
> I am also confused about Figures 38 and 39. Are these the projections 
> of figures 36 and 37 in different units?
>
yes. will add clarification.
> p. 32. Are the 1.58 and 2.56 number coming from Figs 38 (mean 2.619) 
> and 39 (1.657)??
> The procedure needs clarification.
>
yes, will do.
> p. 35.
> Instead of using "top left to bottom right" on these plots use "left 
> to right, top to bottom". Also add bin widths (0.4 GeV?)
>
will do.
> p. 37. 5.2 Integration over the Breit-Wigner
> The integral is infinite, so you need to define the range of 
> integration (in units of the full width Gamma)
>
from -2 Gamma to +2 Gamma
> 37, 5.3 Side band extraction...
> The discussion in this section would be helped tremendously if you 
> take a single energy bin from Fig 41, 42 and 43 and replot so that all 
> information can be visible. You can then use that series of plots to 
> explain the procedure and give specific numbers for that bin. The 
> discussion is sufficiently convoluted that without being able to read 
> any information from the small plots, the discussion is difficult to 
> follow.
>
Good idea, will do.
> 3rd line second paragraph p 38
> " Cut away the invariang mass peak according to the PDG": Do you mean 
> : Fit do data outside the mass range of 1385 - Gamma to 1385 + Gamma? 
> Give specific numbers for these (not just refer to PDG).
>
Yes, you are right. Its actual used numbers (peak and width) are photon 
energy dependent. They will be listed in a table.
> p. 40 5.4 last sentence
> use "measured" instead of "real"
>
will do
> p. 45 5.7
> Define t'
>
will do
> p. 46 t plots
> It seems like the fits do not include the last data points in the 
> first series of plots. Did you omit them, or does the fit just not 
> plot that far? If omitted, why?
>
You are right. It is omitted. There are several reasons on that.
The top reason is that in my opinion, t slope behavior is valid only in 
t channel production. The t channel production dominates in the most 
forward angle corresponding to the region with small t prime. Other 
reasons include low statistics, large error on acceptance due to low 
momentum of k+.
> p. 47, 6.1 & 6.2
> If the event sample is the same for the fiducial volume and pi 
> momentum studies, the statistical errors are not independent, so 
> comparing the extracted data points to the statistical uncertainties 
> is not valid. You should also attempt to extract an quantitative 
> number from the plots. One possibility is to take the average (over 
> energy) deviation between extractions and quote that as your 
> systematic uncertainty. But you need a number.

I don't quite understand the first part. I didn't compare fiducial cut 
and pi momentum cut. There is no cut on pi- momentum in fiducial cut either.
I can get a number from those.

> p. 52 Table
> Reference -> See Section
>
will do
> p. 56 -58 Figs 62-64
> See general comments.
> Also: Instead of just citing [3] at the end of the sentence, you 
> should state "Data taken from Ref. [3]" to make it clear.
>
will do.
> p. 56 following eq 3
> Next to last sentence, use variables
> The angle distribution for Sz=1/2 should behave like the first term, 
> alpha, and the Sz=3/2 state should behave like the second term, beta, 
> of Eq. 3.
> You need to add a comment about gamma. What does this represent? Is it 
> an interference? [Note that you change notation to mz in the figure 
> captions. You may wish to make them consistent.
>
will do on gamma.
Which figure? Is the figure from Lei Guo?
> p. 58, before 7.3
> The "preliminary" data of Guo? I thought these data were published?? 
> If not you need a better reference than "private communication"
>
I don't think it's published so far as I know. It may be wrong. He 
published the cross section in NStar05 (hep-ex/0601010) and these 
figures were not there.
> p. 58. Results, last two sentences first paragraph
> ...the distribution is fitted TO EQ 3 and plotted in Fig. 64. The 
> ratios beta/alpha and gamma/alpha (?) for different photon energies 
> are shown in Fig. 65.
>
will do.
> p. 59 Fig 65 caption
> I believe the first sentence refers only to the red data. You should 
> add a description of the blue data points.
>
will do.
> p. 59 first sentence
> Again, use variables beta/alpha, gamma/alpha to make the text cleaner.
> The discussion about the Chi2 is unclear to me and the discussion 
> should be amplified, with a reference to Fig 66 (currently missing).
>
will do and discussion about Chi2 is to describe the way of extracting 
errors.

>
> p. 61 Summary
> second line, should this be 1.5 GeV?
> first line second paragraph
> On the other HAND, the production....
>
You are right. It's from 1.5 GeV although the first bin center is 1.75 GeV.
will replace way by hand.
> middle second paragraph:
> In case of more than one possibilities, the ratio of them is the same 
> instead: I do not understand this sentence.
>
We had trouble of describing this idea clearly. I will think about it again.
> I suggest you add two plots combining data from 62 and 65: Plot 1: 
> Ratio beta/alpha for Sigma*- and Sigma*0, Plot2: Ratio gamma/alpha for 
> Sigma*- and Sigma*0. That will highlight any differences between the 
> two reactions and will make it easy to discuss, compare and contrast 
> them in the text.
>
will do.
> Generally, it will help to amplify the discussion somewhat and attempt 
> to draw some crisp conclusions. You will need a few sentence 
> highlights for the paper abstract.
>
> Let me know if you have any questions about these comments.  Cheers, 
> Elton
>
Thank you, Elton

Cheers,
Haiyun