http://cms.cern.ch/cds/HIN-13-003
Ernesto
Type B
My understanding is that the result on the integrated double ratio is a kind of groundbreaking achievement in the field of the heavy ions physics. In that respect I have few comments on some of the extra results which are presented in the paper.
- it seems that the comparison with PbPb results is suboptimal. We understand the convenience of using for the comparison the results from 2011 data-taking already published by CMS, but given the large uncertainty in translating the “2011” to “2013” results (e.g. the correction factor mentioned at L153 has a 25% uncertainty) one can think that using PbPb results form 2012-13 dataset would substantially improve the quality of the comparison.
- a relevant fraction of the paper (L239-284) is devoted to the discussion of the differential results of Fig.5 but the conclusion is a bit vague. Do you think that this section should be really maintained as such? I would at least shorten the paragraph with the possible interpretations (L270-284) as it has not a firm conclusion.
Type A
Abstract:
It looks a bit strange that what we think is the main result of the paper (the integrated double ratios being smaller than 1) comes after the discussion of the single ratio vs. the event activity.
\|eta_cm|\ < 1.93 → \|eta_{CM}|\<1.93 “CM” is capital case elsewhere in the text
remove double quotes around “event activity”
The cut on the muon pT>4 GeV could be omitted in the abstract
Text:
L5 should the references “[3-5]” be put at the end of the sentence (e.g. after “state” in L7)?
L42 “characterizing Y family” → “characterizing the Y family”
L50-L51 remove “1)” and “2)”
L61 “sensor elements” → “channels” (“sensor” usually indicates the silicon chunk)
L72 “The direction of the higher energy proton beam” → “In pPb collisions, the direction of the proton beam” (“higher energy” suggests we had also asymmetric pp collisions…)
L86 I think it is confusing to quote an “effective luminosity” (4.1pb-1) as the result of some event selection. Just quote the efficiency of this selection (4.1/5.4 isnt't it?)
L92 “the EVTGEN [21] package” → “EVTGEN [21]”
L93 “Final-state bremsstrahlung” → “Final-state radiation” (unless bremsstrahlung is used to indicate explicitly QED radiation
L98 “passing several quality cuts” → “passing the quality cuts”
L123 “center-of-mass colliding energy” → remove “colliding”
L149 “cold nuclear matter”: not being expert of HI physics, this definition comes a bit out of the blue…It could be probably anticipated in the introduction at the beginning of the paper.
L181-185 there is a quite detailed description of the choice of the binning but it is not clear which is the physical motivation for this choice (e.g. the bins do not have the same fraction of events nor there is a simple proportion between the average measures of the event activity in subsequent bins)
L186 “corrected for detector acceptance” I guess to have values integrated in \|eta_CM\|<1.93(and no other restrictions) . If my understanding is correct one should detail it in the text.
L188-189 why the systematic errors on the Y(3S)/Y(1S) fit are twice those on the Y(2S)/Y(1S) fit. In particular 30% syst. refers probably to a single point (pp N_track>31, rightmost “orange” point in Fig.3/right): Can this fit be improved any further?
L193 “midrapidity track multiplicity” could have been introduced earlier
L195-197 and Fig.3 what are the predictions for these trends in absence of the effect you are looking for?
Fig.1 (right): L_int=5.1 pb-1 → shouldn't it be 5.4 pb-1 as in the text?
Figs.2,3,4,5: the title of the y-axis should have “Y(nS)” instead of “Y(ns)”. What is the convention for the boxes, error bars around the data points? Statistical only and total uncertainty?
Fig.4: these plots seems to be a bit overcrowded… Are the Y(3S)/Y(1S) points really relevant for the discussion, since the corresponding data from PbPb are not available?
Stefano
Type B
The paper, to my understanding, presents new effects that deserve the attention of the HI community. However, these new results need to be presented in a much clearer way, especially in the description of the effects we are seeing. The discussions about possible interpretations are hard to follow and not straight to the point. Several paragraphs need to be reworked.
In particular, with respect to readability, the paper would greatly benefit from sectioning. In facts, according to CADI, this work is aimed at JHEP, which recommends sectioning.
In the discussion of systematics related to fitting, nothing is said about the uncertainty on the parameterization of the signal. That is, CB parameters are derived from a fit, with their errors. How is that error reflected in the estimate of the yields and ratios ? Roofit provides the machinery to vary parameters according to their error matrix.
The fits seem to systematically present one or more high points in the valley between the Y1S and the Y2S. Have you tried a double-sided xtal ball ?
Type A
- When printed, figures show a grey-ish background. Please check and in case remove grey background in favor of plain white. Remove “Preliminary”
- Abstract: “Upsilons, which decay into muons of transverse momentum above 4 GeV etc”. Consider something like “Upsilons detected via their mu+mu- decay, in the kinematical region etc …” , or simply “ where both muons have transverse momentum etc.”
- “as a function of two measures of “event activity” ” → no quotes in “event activity”. Consider changing to somewhat like “ studied as a function of event activity”, which in turn is quantified using two observables: etc.. “
- “yields normalized to their event average” - remove “normalized by their event average”: it's in the formula, and can be explained later. I don't know what an “event average” is.
- remove : “different amount of particles accompanying the production of Y”, it's already said in the previous sentence.
- “the ratios .. show a smaller variation” → consider changing to something like “ratios are more stable if measured as a function …”
L18-29: the word “states” is repeated at least 9 times L 34 : “it is noted that … could be accompanying different quarkonium states”. Consider reworking as “it is noted that different quarkonium states could be characterized by distinct event signatures”
L42: “characterizing the Y family” → add “characterizing the production of the Y family ”
L42-54: this paragraph is very important and needs to be written in a clearer and more linear way. Avoid storytelling (“first .. then”) in favor of a more direct approach, f.i. “we have measured single and double ratios of the yields” and then explain exactly what the ratios are.
L49: “corrected to full single-muon transverse-momentum coverage”. Meaning unclear. No hyphen in “transverse momentum”.
L55: “integrated over all event activity”. How does one integrate over “all event activity” ? Seems difficult to integrate over an abstract concept.
L74 :“after 18 nb-1 were taken” → “after an integrated lumi of 18nb-1 was collected”.
L84: “simultaneous collisions” add qualifier (per event, per bunch xing, per trigger ? )
L90 : “Simulated Monte Carlo” : remove “simulated”
L129: “down to a level which is negligible …” → consider replacing with “within our uncertainties”
L130: “to assess the latter” : “latter” refers to .. ?
L135 : “from the above-mentioned signal extraction” → “from the signal extraction procedure described above”
L137 : “two energies ” → “two center-of-mass energies” L140 : “stronger” → more strongly (or something better) L145 : remove “CMS” 154-156: consider shortening by a good amount : “normalized by the lower-statistics pp … in 2011. Normalization to 2013 data was not considered because of the large systematic uncertainties it would imply, due to the different trigger and reconstruction algorithms”.
L169: “the single ratios signal the presence” L171, 172 “one Pb ion .. two Pb ions” → do we really need to specify ?
L181-185: it's not clear why this complicated binning is devised.
L210: Remove “the effect reflects itself” → “The pp sample contains on average two extra tracks per event”. Consider giving right a way a hint to the fact that this is due to feed-down
L204: “one artificially lowers the number” : not understood
L209: “typically assumed feed-down fractions” → “the feed-down fractions retrieved in literature [ref]”
L212: “converted-photon reconstruction efficiency is too low” → “photon conversions cannot account for the observed increase in multiplicity.”
L221: “narrow correlation” → correlation is either weak or strong I believe.
L265: “as well as by the absence of sensitivity of … observable to a modification that is flat versus event-activity” → please rephrase
Giacomo
Type B: The paper presents some new and interesting results, that clearly have a large impact on the HI community as provides important results on the initial state effects estimates. I think such results deserves some further improvement in how they are presented. The flow of the text can be largely improved by rephrasing and reorganizing it. As it is now, there are arguments that are presented, then abandoned and then discussed again in some other part of the article, as well as some repetitions. It kind of looks like a copy-and-paste of different texts. It would be better reorganize the text in some “smoother” way. Some more sectioning (and referencing to the sections inside the text) of the text would as well help the reader, as several topics are discussed.
Type A: 8 “at stages […] bound state,” ⇒ this phrase looks redundant and imo shifts the reader attention from the main point (which is that initial/final conditions can affect the yields as well as QGP)
56 “elsewhere” → “in” 56 “central”→“main”
121 Why is it “conservative”? From the explanation it looks to me that the systematic uncertainty is properly evaluated, and therefore is not conservative. I would remove this adjective, or explain why the systematics is overestimated.
fig. 2: pp markers have a different colour between legend and plot. Should be corrected in the final figure [optional]You may also consider to explain explicitely the arrow in the caption
171-172 Remove ”(one Pb ion)“ and ”(two Pb ions)“. At this point of the paper you used this notation several times already.
169-173 Is there any reference that is worth to add in this paragraph to explain the physical meaning of the single ratio measurement?
197-199 “The Y(2S) … upper limit” This part discusses fig2. I think it will help the reader to move it to before, and if you feel it's really needed put a simple reminder in line 194.
At line 214 you conclude that the decreasing trend of Y(nS)/Y(1S) vs Ntracks can't be explained by selections or feed-down. Then the issue is abandoned until line 270, thus forcing the reader to go back and forth in the paper. It would be better to reorganize a bit the discussion moving lines 270-284 after line 214, or (worst, in my opinion) anticipating in line 214 that the effect is discussed later in the paper if you want to keep it as it is.
Riccardo
Abstract Overall, I think it needs to be reworked out. It gives too many details, while on the other hand does not really explain in a convincing way what is the actual measurement. The results have been put down as factual, while their are the actual measurement, e.g. (but it is only _one_ example), it is written: “the ratios of the excited to the ground state decrease with […]”, I would rewrite underlining that it is a result, to sound something like: “we found that the ratios of the excited to the ground state decrease with […]” (this is one example).
Going also point by point to the abstract text: - I suggest to remove the quote from “event activity”, quotes in general gives an idea of approximation (meaning that what is quoted is not the appropriate term to describe something). - The sentence “The Y yields normalized by their event average” is actually not meaningful - ”[…] on the three states“, at the first readings, one wonders what these “three states” are, as they are never introduced before. Rephrase such that it is clear that we refer to 3 different Y states. - ”[…] measured as a function of the transverse energy.“, transverse energy of what? It is unclear from the abstract only.
General Comment
I must admit that having the text written as a unique section makes uneasy the reading, make sections would be of great benefit from the reader point of view.
Line by line comments:
L19: “long after”, I do not like it, we have not a time measurement to support that.
L19-20: remove the quotes
L23: as it is written the sentence, it seems that “their” refers to processes. The sentence should be rewritten.
L25-L29: With the amount of information given in the previous 24 lines, it is not clear what conclusion one should drive from L25-29.
L48: Not clear what you mean with “corrected to a full single-muon transverse-momentum coverage”.
L50: Transverse energy of what? Total? Not clear with the info available at this point of the paper.
L52: “a central region” –> “the central region”
L53: individuals –> Y(nS)
L54: you want to sue the construct “both … and …”, but then you put in parenthesis part of it. Remove the parenthesis.
L54: the sentence “normalized … activity” is hard to read. Please rephrase it (perhaps, it just need to drop the word collision).
L86-89: I do not understand. The selection make a bias in the computation of the event-activity variable, then you apply it for that specific analysis? Are you sure that the “It” which starts the sentence has the meaning that you want?
L88-89: What do you mean? That you did not removed the high-pu _events_? Otherwise I cannot see how you would lower the size of your sample, by removing pu collisions (which written like that means additional collisions in the same event as the one of your interest).
L88: “lose statistics” is jargon, either refer to the size of the sample or to the statistical uncertainty, not to the statistics itself.
L92: remove the pythia version from the text
L94: it is a bit reductive. I would rephrase to sound like: “The detector response is simulated with GEANT4[23], interfaced with the CMS Software. The simulated events are reconstructed using the same algorithms as for the data”.
L98: why 1.93 and not 1.9 or 1.95?
L100-101: Not clear what is the symmetry you write about.
L121: “taken as a conservative” –> “taken conservatively as”
L188: remove ”(described below)“
L219-229: It is unclear if you make directly use of the PbPb data too. If so, it should be stated in the list of the used samples in the analysis.
TYPE B like: L230-238: I was convinced (L9-13) that pp and pPb can explore different physics mechanisms than PbPb. Now here you put everything together, and one naively expects differences that at least can be partially explained by the models you describe in the introduction. I think therefore that L236-238 is a bit inadequate as comment to the differences between the three systems.
L244: “does not cancel” –> “does not cancel out”
L255: “J/psi measurement”, I do not think exist a “J/Psi measurement”, do you mean “measurement with J/psi” or “measurement of j/psi yield” or ?
Figures:
- All (or almost) y-axis labels need a bit more off-set to not overlap with scale labels.
- In several figures (i.e., 2,3,4 and 5), Y(ns) –> Y(nS) in the y-axis labels
Caption Fig.1: “black circles” –> “black dot” or “black solid circles”
Fig.2 left: the Y(3S)/Y(1S) bin has different marker styles that what reported in Y(2S)/Y(1S) bin, please make use of one style only, also to be consistent with the legend
Fig.3,4,5: it is not described in the caption what are the shaded regions around the points.
Fig.3: right plot reports twice the word “preliminary”. Btw, isn't it for paper? Sure that we have to use the word “preliminary” at all in the plots?
TYPE B like: Fig.3,4,5: Why the error on x of the points is not displayed?
Fig.4: the eta region fiducial cut is displayed twice. Can you put |y|<1.93 below the first column of the legend, more or less in the same position as |y|<2.4?
Tab 1: what is the uncertainty on the <N> and <ET>? We shall write them and also put the relative bars in the relevant plots (see above).
Stefano C.
TYPE B
- The title does not match exactly the content of the paper
- I think that using the 2011 PbPb results as a reference is not 100% fair and the justification given at L150-159 still leave me doubtful, given that there seems to be some tension between the pp single ratios measured in 2011 and 2013
- In general the article reads fine to me (even though I am far from being an expert of the topic). Still I think it can be improved:
- -maybe it's too long, and it can be shortened first of all by avoiding repetitions
- -since the content it's clearly divided into 3 measurements, maybe dividing it in sections accordingly would be good for the readibility
- where available and if feasible: overlay theoretical predictions in the plot
TYPE A
L 44: maybe the list of the cuts can be dropped, since it is repeated at L98
L 80: “electromagnetic” what?
L 85-86: why quote the luminosity after the cuts? I think it is misleading, even though there is no “absolute” measurement in the paper
L 102: no need to say this IMO
L 111-112: has it been checked that the resolution does not depend on the event activity? If yes maybe it is wort mentioning
L 162: “global” → “other”?
L 169: “and/or”: I don't like it
L 175: I don't like the abbreviation for variable 1) since it is at the me time difficult to read and does not exactly match the eta coverage which is > 4 but also < 5.2 Consider something like E_{T}^{fwd}
Figure 3: consider dropping it and leave only figure 4
L 181-185: the binning is discussed in details but I cannot see a justification for this “complicated” choice. If there is one please mention it
L 262-265: the statement is not clear to me (probably my fault)