28 December 2010 - version 4.0 PionHbtInPP_v4.0.pdf
6 April 2010 - version 3.2 PionHbtInPP_v3.2.pdf
This is the version submitted to PRC.
27 March 2010 - version 3.1 PionHbtInPP_v3.1.pdf
Our responses to the comments from the Collaboration review
7 January 2010 - version 3.0 PionHbtInPP_v3.0.pdf
This is the one sent out of the GPC to the collaboration.
28 December 2009 - version 2.3 PionHbtInPP_v2.3.pdf
Our responses to GPC comments to v2.2
Finally, there were a few other changes, most related to figures, that were made in going the final step from v2.2 to v2.3, that are not in direct response to GPC comments. These may be found here.
16 December 2009 - version 2.2 PionHbtInPP_v2.2.pdf
Our responses to GPC comments to v2.1 from
Small changes needed in figures. I want to collect these small changes and then ask Zibi to implement them all at once.
30 November 2009 - version 2.1 PionHbtInPP_v2.1.pdf
Our responses to GPC comments to v2.0 from
Updates needed for next version:
July 14,2009 - version 2 - PionHbtInPP_v2.pdf
Our responses to comments to v.1.2 received from:
July 6, 2009 - version 1.2 - PionHbtInPP_v1.2.pdf
Minor updates:
June 29, 2009 - version 1.1 - PionHbtInPP_v1.1.pdf
Updates of figures:
Text updates:
June 16, 2009 - version 1 - PionHbtInPP_v1.pdf
Here are the comments from the collaboration to version 3.0 of the pion HBT paper from p+p collisions, and the PA responses:
From the BNL group - (they sent in a pdf file of comments; we paraphrase their feedback, here)
1) suggest changing title to "PION femtoscopy in p+p collisions at RHIC"
-- we agree. Done. In fact, as per IOPP suggestion (below), we also replace RHIC with 200 GeV.
2) Why don't we normalize the correlation function to unity, but leave it at 0.82?
-- the main reason is that there is no "flat region" at large q, over which to normalize the CF. This is one of the main themes of this paper. We could normalize the plot so that the CF comes "near" unity, but this is really arbitrary. Very important: this normalization issue does NOT affect HBT radii or other fit parameters, since the overall normalization is an overall parameter. This is true for all HBT analyses.
3) <Pz>=0.32 seems too high for pions.
-- this comment is concerned with the EMCIC parameters listed around line number 532. Please note that it is the average value of Pz-squared that is 0.32. Probably even more important to this comment, please note also that this number is not for the measured pions, but for all particles emitted from the effective source. Take a look at the discussion and formalism in [44]. (See e.g. Tables 1 and 2 from that paper.)
4) Why does Figure 6 show fit parameters from zeta-beta fit, but Figure 7 does not?
-- The zeta-beta fit is only applicable for three-dimensional correlation functions. Figure 6 shows parameters to a fit to 3D correlation functions, while Figure 7 is only for one-dimensional correlation functions.
5) Figure 12 is missing a label on the y-axis of the lower panel.
-- thanks, this is fixed.
6) Clarify which formula-- equation 7 or 8-- is used to get the parameters plotted in figure 14.
-- thanks for catching it. it is Eq 8, and it says so now in the paper.
7) Explain the x-axis on Figures 13 and 14. Why <pT> and/or sqrt(2/3)|p|?
Yes, these x-axes were a big mess. We've cleaned it up; please take a look now. The issue was simply that NA22 and NA27 reported the total momentum (not transverse) of the pair. In order to compare it to ours, we assumed isotropic emission, and as a proxy say pT=sqrt(2/3)|p|. Not ideal, but it seems the best we could do, or?
8) make usage (italic versus roman) consistent, when writing "Au+Au", "p+p" "e^++e^-" etc.
-- done
9) When starting a sentence, use "Figure," but otherwise use "Fig."
-- okay done.
Comments from Spencer Klein 18 Jan:
This is a very nice paper, presenting a very carefully done physics analysis. Nice. Although I have no comments on the physics, I do have a few comments on the presentation. I acknowledge that many of these comments are a bit 'squishy;' feel free to ignore them if you don't like them.
Line 131 - 'soft sector' is pretty slangy.
Okay, now we have removed that term until we mention Pythia in the Discussion section. There, "soft sector dynamics" is discussed explicitly in the reference given.
On line 177, it's not clear what you mean by 'reconstruction system.' If this refers to tracking software, etc. say so.
Yes, this is essentially it. We say "reconstruction software," now.
There are a few spelling mistakes: 'measurements is misspelled (differently) on lines 139 and 204, 'briefly' is misspelled on line 395, and 'resonance' on line 750.
Thanks. Fixed.
Line 184+ seem a little overblown.
Hmmm, okay we have slightly toned down, replacing "We hope that our results may eventually lead to a deeper understanding..." with "These results may play help in understanding..."
Line 336 says 'we will use the name '\delta-q' when the above formula...' Is this Eq. (12) or Eq. (13)? This should be clarified.
Well, we use Equation 12 for 1D correlation functions and 13 for 3D correlation functions. This is clarified now in the sentence following the formulae.
Since this is not a letter, could you add a little bit about the trigger conditions to Section III? You later show that multiplicity affects the measured radii, and multiplicity can depend on the trigger conditions.
Okay, we have added some information about the trigger, based on BBC coincidence, at line 450.
Likewise, could you say something about how diffractive events are handled? Our trigger is sensitive to doubly-diffractive events (i.e. where both nuclei break up diffractively); previous STAR pp papers have accounted for the diffractive events, at least crudely. If I remember correctly, they were between 10 and 20% of the cross-section. Could you say a little bit about how these events affect the radii? It seems to me that, at least, this is a systematic uncertainty.
Actually, we do not correct for doubly-diffractive events in our earlier papers, but only say that they could give a contribution on order 11% for the yield integrated over all rapidity. At midrapidity, the contribution to the yield is significantly less, and the contribution of pairs at midrapidity will be much smaller yet. But the point is that we are measuring the radii for NSD, just as in previous papers (e.g. R_AA) we measured spectra for NSD. To the extent that DD contributes, it is included.
Line 437 'it was only a 1% of the femtoscopic radii' isn't very clear. Can you rephrase, with a little more clarity about what 'it' is, and where the 1% comes from?
Now we say in particular what was done, which was that we played around with PID cuts (cutting on dEdx, or nsigma), being very "strict" or opening up the cuts all the way, and saw very little change in radii (1%).
I would suggest looking at the section that compares our pp results with the worlds pp data, to see if it can be shortened, and if the promises that are made early on can be toned down - the conclusions to that comparison are (necessarily) not very crisp, and people may be left a little bit disappointed. The analysis is beautiful - very detailed - but it unfortunately doesn't lead to a clear conclusion.
Figs. 11, 12 and 15 cover a rather wide range of experiments. I'm wondering if a sentence or two about them would be worthwhile (I recognize that this contradicts my previou comment).
Line 679 'experiments did not follow a standard method of measuring and reporting multiplicity...' I don't think that there was a standard method than; this sounds a little negative toward the experiments. Can you rephrase?
We did tone down somewhat the promise at the beginning ("hope it leads to deeper understanding" etc); hopefully people don't feel too disappointed after that, but who knows. I guess I see what you mean about negative tone regarding past experiments, but, between you and me, I am really shocked when I look at these old measurements. I mean, did they not talk to each other at ALL? Did they not want to compare to each other at ALL? But okay, who knows what people will say about our papers in 20 years; indeed, who knows what they are saying now?
We have moderated the negative tone; I hope it's better.
LEP ran at several different energies, most notably at the Z^0 peak (~ 91 GeV) and above W^+W^- threshold (> 180 GeV), and, I believe, published HBT radii at both. Can you add the energies for the points to Fig. 15?
All of the radii shown are indeed at 91 GeV. We've updated the figure to include that information.
A few references - 33, 56 and maybe others, that appear to merit a collaboration label.
Hmmm, well we are trying to use "standard" bibtex directly from SPIRES, and for those papers, the collaboration (E735) isn't listed for whatever reason. But okay we have added them by hand. (I am thinking though that they will disappear again after it goes through the journal.)
Comments From Institute of Particle Physics (Huazhong Normal University) 18 Feb
1) Title: Femtoscopy in p+ p collisions at RHIC ->
Femtoscopy in p+ p collisions at \sqrt_{s} = 200 GeV ?
Okay good idea. In fact, as per the BNL group's suggestion, we preceed it with "Pion Femtoscopy..."
2) Abstract: line 1 and line 4, p+p -> $p+p$
line1/2 at 200 GeV -> at \sqrt_{s} = 200 GeV
Okay, done.
3) Line 111, up to 200 GeV -> up to \sqrt_{s} = 200 GeV
Line 112, d+Au -> $d+\mathrm{Au}$
Line 131, in the soft sector-i.e. at low pt. ->
in the soft sector, i.e., at low pt.
Okay, done.
4) Line 193, The paper is organized as follows ->
The rest of the paper is organized as follows
Well, we see your point, but prefer the wording as it is, so we didn't change it. Let us know if you feel very strongly.
5) Line 221, $Q_{inv}$ -> $Q_{\mathrm{inv}}$, everywhere,
$R_{inv}$ -> $R_{\mathrm{inv}}$, everywhere
okay done.
6) Line 228 and 236, “o,” “l” and “s” ->
“$o$” “$l$” and “$s$”
done
7) Line 430, 439, ... MeV/c -> $\mathrm{MeV}/c$, everywhere
done.
8) III Analysis details, are there any nhit, dca cuts in your analysis?
We have left most of the cut details to reference [49] (our long HBT paper), since a main point is that we do identical analysis. However, we now mention explicitly that we require at least 10 hits and a DCA less than 3 cm.
9) Line 481, GeV/c -> $\mathrm{GeV}/c$, everywhere
done
10）.In line 689, is it "pT-dependence" or "mT-dependence"?
Well, since we only discuss one particle species, they are equivalent.
11) Line 749, 808, $Au + Au$ -> $\mathrm{Au} + \mathrm{Au}$
Line 782, 803, 805, p+p -> $p+p$
Line 803, A+A -> $A+A$ or $AA$
done
12) Line 812, 813, why we need "-" here?
Now that you point it out, that sentence wasn't very good. We've reworded it, without any "-".
13) Fig 1, could we make the label "q_{o, s, l} [GeV/c]" larger? The
label size for different Fig are different, Should we make them same ?
We have made the label larger on Figure 1.
For the other figures, we think they are readable, so can remain for now.
14) Fig 3 and 5, $A_{22}^{RE}$ overlaped with data points.
Okay fixed.
15) Fig 7, caption, $R_{inv}$ -> $R_{\mathrm{inv}}$. Same thing in the
table V, VI, VII.
Okay fixed.
16) Fig 8, try this if PAs used root,
<dNch/deta> -> #LT dN_{ch}#/deta #GT, also, $R_{inv}$ -> $R_{\mathrm{inv}}$.
Nice, thanks on the #LT, etc!
17) Fig 9, $Au+Au$, $Cu+Cu$ -> $\mathrm{Au} + \mathrm{Au}$, \mathrm{Cu}
+ \mathrm{cu}.
Done.
18) Fig 11, 12, <dNch/deta> -> #LT dN_{ch}#/deta #GT. same as Fig 8.
Done.
19) Fig 14, the label for the x axis should be a little bit far away
from the axis.
Done.
20) reference [1] - [4], the journal information should be added.
(Please check all references.)
Okay, done. There were a few more that needed journal info added.
Actually, it seems we don't need the arxiv
number if the paper has been published.
well, we are doing straight bibtex from spires. The arxiv info can be included, or not, according to the style file. PRD has their own style file, so will format it all at once.
reference [14], why we need website here?
beats me! I've removed it manually. (spires bibtex had it included, for some reason!)
Comments from JINR (Jan Fedorisin, Peter Filip, Richard Lednicky and Stanislav Vokal for JINR)
Abstract: What about to put "200 GeV" in one line?
Done.
109: "The extraordinary flexibility of the machine"
Since e+A and p+A collisions are not yet possible,
it can better be reformulated as:
"High flexibility of the machine"
Hmm, usually I'm not much for cheerleading, but in this case, I strongly want to keep the wording. With such a range in energy, polarization possibility (transverse and longitudinal), and asymmetric systems, RHIC deserves to be called "extraordinarily flexible."
139: measuresments -> measurements
fixed. Thanks.
There are many comments on the term "HBT," which I collect here:
144,398: "HBT radii" -> femtoscopic radii
There is a huge amount of "HBT" garbage which, in most cases,
can be removed or substituted:
199,246,396,531,550,611,
689,701,710,760,774,787 : HBT -> femtoscopic
247,551,567,574,602,613,
614,629,636,667,675,716,
719,732,740,748,766 and
caption of fig.9 : remove "HBT"
675-676: lower HBT radius, at a given multiplicity ->
lower radius obtained by E735 at a given multiplicity
162: HBT correlations -> Femtoscopic Bose-Einstein correlations
I am certainly a subscriber to the "femtoscopy" nomenclature to describe two-particle correlations arising from the spatio-temporal proximity of particles at freezeout, especially when one is discussing such correlations in general, i.e. for various particle types. However, I see no reason to entirely expunge the term when discussing pions in particular, when this term has seen historical use for pion correlations and when our paper connects to historical data. After all, it's not like "HBT radius" is "wrong." It's just a term. We even explicitly acknowledge this early on, by using the term in quotation marks.
Furthermore, there is another reason why wholesale replacement of "HBT" with "femtoscopic" is a bad idea in this paper. In this paper, we frequently make the distinction between "femtoscopic" and "non-femtoscopic" correlations, a distinction which is not often discussed and about which significant confusion can arise. We mention the radii frequently in the paper, and if we start calling all "HBT radii" as "femtoscopic radii" when we are at the same time referring to "femtoscopic" and "non-femtoscopic" correlations, it will be simply too much.
For both of these reasons, we argue to continue the liberal use of the term "HBT" in this paper.
144: the mass -> the transverse mass
done
146: [13] -> [13,10]
done.
165-166: "less clear and well developed" perhaps should read
"less clear and not well developed"
Good suggestion, thanks.
181-183: into the context both of ... and
(as much as possible) into the context of previous ->
into the context both of ... and
(as much as possible) previous
Okay, except we preserved the "of"
224-225: Pratt-Berttsch "out-side-long"
coordinate system [23,24] ->
"out-side-long" coordinate
system [gra'77,pod'83, 23,24]
add earlier references:
gra'77: P. Grassberger, Nucl. Phys. B 120, 231 (1977).
pod'83: M.I. Podgoretsky, Sov. J. Nucl. Phys. 37, 272 (1983).
(particularly, see eqs. 12,13 in [pod'83])
We have added the Podgoretsky reference, but it not actually clear to us that the Grassberger reference is relevant here. Probably I just missed it, but does he really propose an out-side-long (or equivalent) coordinate system and a fit with three radii? I do see some discussion of q transverse to P and q parallel to P, and cigar shapes, but that's kind of a tenuous connection. There is no (or?) suggestion to analyze in that frame.
283: separation distribution. ->
separation distribution [led'79].
add pioneering reference on the topic:
led'79: R. Lednicky and MI. Podgoretsky,
Sov. J. Nucl. Phys. 30, 432 (1979)
done.
301: vanishes. ->
vanishes [cso'91].
add pioneering reference on LCMS:
cso'91: T. Csorgo and S. Pratt,
Proc. Workshop on Heavy Ion Physics,
KFKI-1991-28/A, p.75.
You are right, we need a reference there. But actually, we found an even earlier one, which is even published and available:
S. Pratt, T. Csorgo, and J. Zimanyi, Phys. Rev. C42, 2646 (1990)
Probably the conference talk was based on that publication.
314: points. ->
points and over the angles of the relative
three-momentum \vec{q} in the pair rest frame.
done.
380: C_F(q). ->
C_F(q), especially taking into account their
rather small values of the radii in p-p collisions.
done. We actually word it "...especially considering the small radius values in p+p collisions."
395: breifly -> briefly
done
431: their the -> their
oops, thanks. done.
481: ...[0.00,0.12] GeV/c.
Why such a range? No comment in text.
Well, there's no reason. It's just to make a picture. In heavy ion papers, one usually projects over a region of 35 MeV or 50 MeV (often without even mentioning it). It's just that's where the bump is.
492: to present -> of present
No, we really want it to say "to present." But we see the confusion-- it wasn't well worded. We have changed "...the determination to present results..." to "...the desire to present results..."
509: ... Black dotted and purple dashed curves ...
and
511: ... Red curves
Colors are OK in the online text,
but how it will be seen in the paper copy?
Well, mentioning colors doesn't harm anything, but you are right--we agree that there should not be ambiguity. Hence, we have changed the one about red curves to "Solid red curves..." That way, the reader who really only uses a B&W printer can cue on the words "dotted" and "dashed" and "solid."
574: R_{inv},extracted -> R_{inv}, extracted
done.
566-591: Perhaps it should be explicitly mentioned why
dNch/deta=7 is chosen to select the events in
low and high multiplicity classes
Okay. Now we say "The choice of the cut was dictated by the requirement of sufficient pair statistics in the two event classes."
652: STAR's -> of STAR's
done. thanks.
651-657: this paragraph requires an improvement,
description of figures 11 and 12 is not very clear.
Okay, we've reworded that paragraph somewhat; hopefully it is better now.
680: Nch -> N_{ch}
fixed.
694-700: Please explain why <mt> and Sqrt(2/3)|p| variables
can be used on the same horizontal axis to compare
Tevatron and STAR data.
Yes, these x-axes were a big mess. We've cleaned it up; please take a look now. The issue was simply that NA22 and NA27 reported the total momentum (not transverse) of the pair. In order to compare it to ours, we assumed isotropic emission, and as a proxy say pT=sqrt(2/3)|p|. Not ideal, but it seems the best we could do, or?
706: lonngitudinal -> longitudinal
oops. fixed.
727: "Additionally Alexander's explanation ..."
sounds too personal. Please replace by
"Additionally, the arguments from [64,65] ..."
Yes, much better, thanks.
736: HBT -> Bose-Einstein enhancement
done.
750: resonannce -> resonance
fixed.
759-764: The sentence starting with "With a very similar ...."
is significantly emotionally NEGATIVE.
The same content can be expressed by a more
appropriate and more neutral statement:
"With a very similar model, Humanic [71] was able to
reproduce femtoscopic radii measured at the Tevatron [34]
only with strong additional hadronic rescattering effects."
Wow, we didn't mean to be emotionally negative, but we see your point. Your suggestion is much better and is in now.
832: remove "Russian Ministry of Sci. and Tech." (no more exists)
Okay, except you need to tell this also to Liz (I guess), since it comes directly from the official STAR acknowlegements document which one gets from the author tools page:
http://www.star.bnl.gov/central/collaboration/authors/
Comments to figures:
Fig.1: Offset of horizontal axis title should be enlarged.
It touches label 0.3.
Ok, it is better now.
Perhaps add links to Eqs. used for the
fits directly on the figure:
measured CF
standard fit (11) \Omega=1
\delta-q fit (13)
\xi-\beta fit (14)
EMCIC fit (15)
In a way it's a nice idea, but we'd rather not put in equation numbers (which may change) into the plot.
Figs.1-5: Fonts in X/Y- descriptions should be larger
and unique;
offset of horizontal axis titles should be enlarged
Ok, it should be a little better now.
Fig.7: Offset of vertical axis title should be enlarged
(it touches label 1.5).
Okay, it is not touching now.
Fig.9: Zeros on vertical axes of the upper plots
overlap with 8's of the lower plots.
fixed.
Fig.10: Y-descriptions should be larger (as on Fig.9.)
They are a little bigger now.
Fig.12: on the left vertical axis (upper half)(lower half)
substitute R_G by R_B/2
and on the left vertical axis (lower half)
add R_G [fm]
on the right vertical axis remove R_G=R_B/2 and R_G
and move up the descriptions of the points
Actually, you got confused because we neglected to put on the axis title on bottom panel. It is tau*c. So, the top panel has the radii (RG or RB/2 if only RB is available), and the bottom has the tau parameter if it exists. Sorry about that. It should be less confusing now.
General suggestions to figures:
1) increase little bit labels offsets for vertical axes
in almost all the figures, especially small ones. Seems the labels
touch the axes in some cases, when small zoom is used. This concerns
also label offsets on horizontal axes in Figures 2,3,4,5.
done.
2) use italic font for writing math symbols on the plots;
Okay.
3) If it is possible, improve the organization of the sections
(mainly IV) containing figures and tables could be improved.
Sometime figures are placed too far (even two pages) from the
text where they are referred to.
What about to put together Figures 2,3,4,5 as well as
Tables I,II,III,IV and V,VI,VII? Firstly, they are related and,
secondly, it would make comparison among them easier.
well, we will play around with it a little bit, but as you know, LaTex has a mind of its own and any little games you play to put figures on a particular page will get all messed up when someone else uses a different style file or some text gets added or something. We'll do a little bit, but mostly it is for the journal to do that formatting.
Some questions:
1) There is not much information in the paper describing the
fitting procedures.
Okay, now we have put into each table, the chi2 and ndf for each fit. We also mention (just before Section II.A) that maximum-likelihood was used, though chi-square fits give almost identical results.
2) It is mentioned at the end of section III that the
systematic errors consist about 10% (for STAR data).
10% of what (in femtoscopic radii ?) ?
Yes, it is the radii. In the manuscript, we say this explicitly now.
3) Were some systematic errors included in fitting process or
only statistical errors were used?
Only statistical errors were included in the fitting process.
4) Which fitting method was utilized? Chi-square, maximum
likelihood, or something else?
5) If chi-square method was used, what are chi-square values
of the fits?
It was max-likelihood (which we say now just before Section II.A), though chi-square give essentially identical results. We now include the chi-square of all fits, in the tables.
6) The number of parameters varies significantly mainly in
non-femtoscopic parts of fitted functions as described in
section II, subsection C. It would be interesting to see and
compare the quality of the fits (chi^2/ndf) and see
covariances (correlations) of the fitted parameters.
The chi-square values are now given in the tables. We don't plan on making covariance contour figures.
7) Are the non-femtoscopic effects taken into account
when obtaining values shown in Table IX?
Ah, thanks. In those fits, Omega=1, consistent with all previous fits of this kind. We say this now in the caption.
8) Why the centrality classes 0-5% and 50-80% are chosen for
the data presented in Figure 10?
No special reason to choose precisely those two. Choosing a central one and a peripheral one gives the message that the ratio is flat for all centralities.
From Bedanga - email 22 Feb 2010
I have read the nice paper and have only
few comments as noted below.
1. Abstract:
two-pion correlation functions from p+p collisions at 200
GeV.
--> may be good to add $\sqrt{s}$
two-pion correlation functions from p+p collisions at $\sqrt{s}$ = 200 GeV.
Okay done.
2. We say:
Our results are put into the context of the world dataset
of femtoscopy in hadron-hadron collisions.
--> however in Fig. 15 we also do comparison with e+ e- data.
Unless we want to focus only on hadron-hadron collisions here.
Well, yes, you are right, we put the e+e- data there just since it was available. But it is not our focus, so we don't need to mention everything in the abstract.
3.
Line 165 &166 :
although the theoretical interpretation of the results is less
clear and well developed.
--> This seems to be not very clear.
It Sounds like it is less clear and at the same time well
developed. Is it want we mean't.
You are right, it was poorly worded. Following the suggestion from Dubna, we have worded it "less clear and not well developed."
4.
In Section V, 197 - 198
we put these results in the context of previous measurements
in Au+Au and elementary particle collisions
--> We make comparison with pp and pbar-p collisions, not sure
if we should call them elementary particle collisions.
Okay. We change it to "...in Au+Au and $p+p(\bar{p})$ collisions."
6.
281
Historically misnamed the “chaoticity” parameter, it generally
accounts for particle identification efficiency, long-lived decays, and
long-range tails in the separation distribution.
---> So do we mean to say that the lambda parameter has no
connection to Chaoticity ?
No. Just that it's never been shown to be due to anything other than the items listed. I'll just take away the "misnamed" and put "called."
7. 437 - 438
The small contamination due to electrons and kaons
impacts mostly the value of l obtained from the fit while it
was only a 1% effect of the femtoscopic radii.
--> Reference will be useful, or are they estimates from this
analysis.
They are estimates from the present analysis. We indicate this now with some more text. See around line 441, where we start "By varying the cuts on energy loss..."
8.
X-axis labels for Figures for example 1,2,3 are small.
Yes, there were several tweaks of figures requested and needed. We have revamped essentially every one. This should be fixed now.
9.
It may be good to give a chisq table for the various fits
shown to the data in Fig. 1 - 4, this may provide a better
idea which fits work well.
Specially when we discuss "None of the functional forms
perfectly fits the experimental correlation function, though
the non-femtoscopic 515 structure is semi-quantitatively reproduced by
the ad-hoc .....
Okay, we have actually included chi2/ndf now for ALL of the results, in the tables. Good idea.
10.
The dNch/eta in the Fig's 9, 11 and 12 are corrected for efficiency or raw
values from STAR ?
Those are the raw values.
While in Fig. 11 and 12 it is mentioned in the axis
that it is the average value for Fig. 9 it is not.
Okay you are right; we make it consistent now by labeling Figure 9 to say average value, too.
11. 706
the “lonngitudinal” direction
-->
the “longitudinal” direction
fixed, thanks.
Comments from the BNL group Comments_to_the_paper_-_HBT.pdf
Comments from the Institute of Particle Physics
1) Title: Femtoscopy in p+ p collisions at RHIC ->
Femtoscopy in p+ p collisions at \sqrt_{s} = 200 GeV ?
2) Abstract: line 1 and line 4, p+p -> $p+p$
line1/2 at 200 GeV -> at \sqrt_{s} = 200 GeV
3) Line 111, up to 200 GeV -> up to \sqrt_{s} = 200 GeV
Line 112, d+Au -> $d+\mathrm{Au}$
Line 131, in the soft sector-i.e. at low pt. ->
in the soft sector, i.e., at low pt.
4) Line 193, The paper is organized as follows ->
The rest of the paper is organized as follows
5) Line 221, $Q_{inv}$ -> $Q_{\mathrm{inv}}$, everywhere,
$R_{inv}$ -> $R_{\mathrm{inv}}$, everywhere
6) Line 228 and 236, “o,” “l” and “s” ->
“$o$” “$l$” and “$s$”
7) Line 430, 439, ... MeV/c -> $\mathrm{MeV}/c$, everywhere
8) III Analysis details, are there any nhit, dca cuts in your
analysis?
9) Line 481, GeV/c -> $\mathrm{GeV}/c$, everywhere
10）.In line 689, is it "pT-dependence" or "mT-dependence"?
11) Line 749, 808, $Au + Au$ -> $\mathrm{Au} + \mathrm{Au}$
Line 782, 803, 805, p+p -> $p+p$
Line 803, A+A -> $A+A$ or $AA$
12) Line 812, 813, why we need "-" here?
13) Fig 1, could we make the label "q_{o, s, l} [GeV/c]" larger? The
label size for different Fig are different, Should we make them same ?
14) Fig 3 and 5, $A_{22}^{RE}$ overlaped with data points.
15) Fig 7, caption, $R_{inv}$ -> $R_{\mathrm{inv}}$. Same thing in the
table V, VI, VII.
16) Fig 8, try this if PAs used root,
<dNch/deta> -> #LT dN_{ch}#/deta #GT, also, $R_{inv}$ ->
$R_{\mathrm{inv}}$.
17) Fig 9, $Au+Au$, $Cu+Cu$ -> $\mathrm{Au} + \mathrm{Au}$,
\mathrm{Cu} + \mathrm{cu}.
18) Fig 11, 12, <dNch/deta> -> #LT dN_{ch}#/deta #GT. same as Fig 8.
19) Fig 14, the label for the x axis should be a little bit far away
from the axis.
20) reference [1] - [4], the journal information should be added.
(Please check all references.) Actually, it seems we don't need the arxiv
number if the paper has been published.reference [14], why we need website here?
Comments from the JINR group
Comments to the STAR paper "Femtoscopy in p+p collisions at RHIC"
(Jan Fedorisin, Peter Filip, Richard Lednicky and Stanislav Vokal for JINR)
Abstract: What about to put "200 GeV" in one line?
109: "The extraordinary flexibility of the machine"
Since e+A and p+A collisions are not yet possible,
it can better be reformulated as:
"High flexibility of the machine"
139: measuresments -> measurements
144,398: "HBT radii" -> femtoscopic radii
144: the mass -> the transverse mass
146: [13] -> [13,10]
162: HBT correlations -> Femtoscopic Bose-Einstein correlations
165-166: "less clear and well developed" perhaps should read
"less clear and not well developed"
181-183: into the context both of ... and
(as much as possible) into the context of previous ->
into the context both of ... and
(as much as possible) previous
224-225: Pratt-Berttsch "out-side-long"
coordinate system [23,24] ->
"out-side-long" coordinate
system [gra'77,pod'83, 23,24]
add earlier references:
gra'77: P. Grassberger, Nucl. Phys. B 120, 231 (1977).
pod'83: M.I. Podgoretsky, Sov. J. Nucl. Phys. 37, 272 (1983).
(particularly, see eqs. 12,13 in [pod'83])
283: separation distribution. ->
separation distribution [led'79].
add pioneering reference on the topic:
led'79: R. Lednicky and MI. Podgoretsky,
Sov. J. Nucl. Phys. 30, 432 (1979)
301: vanishes. ->
vanishes [cso'91].
add pioneering reference on LCMS:
cso'91: T. Csorgo and S. Pratt,
Proc. Workshop on Heavy Ion Physics,
KFKI-1991-28/A, p.75.
314: points. ->
points and over the angles of the relative
three-momentum \vec{q} in the pair rest frame.
380: C_F(q). ->
C_F(q), especially taking into account their
rather small values of the radii in p-p collisions.
395: breifly -> briefly
431: their the -> their
481: ...[0.00,0.12] GeV/c.
Why such a range? No comment in text.
492: to present -> of present
509: ... Black dotted and purple dashed curves ...
and
511: ... Red curves
Colors are OK in the online text,
but how it will be seen in the paper copy?
574: R_{inv},extracted -> R_{inv}, extracted
566-591: Perhaps it should be explicitly mentioned why
dNch/deta=7 is chosen to select the events in
low and high multiplicity classes
652: STAR's -> of STAR's
651-657: this paragraph requires an improvement,
description of figures 11 and 12 is not very clear.
680: Nch -> N_{ch}
There is a huge amount of "HBT" garbage which, in most cases,
can be removed or substituted:
199,246,396,531,550,611,
689,701,710,760,774,787 : HBT -> femtoscopic
247,551,567,574,602,613,
614,629,636,667,675,716,
719,732,740,748,766 and
caption of fig.9 : remove "HBT"
675-676: lower HBT radius, at a given multiplicity ->
lower radius obtained by E735 at a given multiplicity
694-700: Please explain why <mt> and Sqrt(2/3)|p| variables
can be used on the same horizontal axis to compare
Tevatron and STAR data.
706: lonngitudinal -> longitudinal
727: "Additionally Alexander's explanation ..."
sounds too personal. Please replace by
"Additionally, the arguments from [64,65] ..."
736: HBT -> Bose-Einstein enhancement
750: resonannce -> resonance
759-764: The sentence starting with "With a very similar ...."
is significantly emotionally NEGATIVE.
The same content can be expressed by a more
appropriate and more neutral statement:
"With a very similar model, Humanic [71] was able to
reproduce femtoscopic radii measured at the Tevatron [34]
only with strong additional hadronic rescattering effects."
832: remove "Russian Ministry of Sci. and Tech." (no more exists)
Comments to figures:
Fig.1: Offset of horizontal axis title should be enlarged.
It touches label 0.3.
Perhaps add links to Eqs. used for the
fits directly on the figure:
measured CF
standard fit (11) \Omega=1
\delta-q fit (13)
\xi-\beta fit (14)
EMCIC fit (15)
Figs.1-5: Fonts in X/Y- descriptions should be larger
and unique;
offset of horizontal axis titles should be enlarged
Fig.7: Offset of vertical axis title should be enlarged
(it touches label 1.5).
Fig.9: Zeros on vertical axes of the upper plots
overlap with 8's of the lower plots.
Fig.10: Y-descriptions should be larger (as on Fig.9.)
Fig.12: on the left vertical axis (upper half)(lower half)
substitute R_G by R_B/2
and on the left vertical axis (lower half)
add R_G [fm]
on the right vertical axis remove R_G=R_B/2 and R_G
and move up the descriptions of the points
General suggestions to figures:
1) increase little bit labels offsets for vertical axes
in almost all the figures, especially small ones. Seems the labels
touch the axes in some cases, when small zoom is used. This concerns
also label offsets on horizontal axes in Figures 2,3,4,5.
2) use italic font for writing math symbols on the plots;
3) If it is possible, improve the organization of the sections
(mainly IV) containing figures and tables could be improved.
Sometime figures are placed too far (even two pages) from the
text where they are referred to.
What about to put together Figures 2,3,4,5 as well as
Tables I,II,III,IV and V,VI,VII? Firstly, they are related and,
secondly, it would make comparison among them easier.
Some questions:
1) There is not much information in the paper describing the
fitting procedures.
2) It is mentioned at the end of section III that the
systematic errors consist about 10% (for STAR data).
10% of what (in femtoscopic radii ?) ?
3) Were some systematic errors included in fitting process or
only statistical errors were used?
4) Which fitting method was utilized? Chi-square, maximum
likelihood, or something else?
5) If chi-square method was used, what are chi-square values
of the fits?
6) The number of parameters varies significantly mainly in
non-femtoscopic parts of fitted functions as described in
section II, subsection C. It would be interesting to see and
compare the quality of the fits (chi^2/ndf) and see
covariances (correlations) of the fitted parameters.
7) Are the non-femtoscopic effects taken into account
when obtaining values shown in Table IX?
8) Why the centrality classes 0-5% and 50-80% are chosen for
the data presented in Figure 10?
From Michal Sumbera [5 Aug 2009]:
Generally I found the article hard to read at some places but this can be
improved if we work on it a bit. My feeling is that this has something to
do with a lot of material and analysis techniques employed. You refer
quite often to your own publications wheer those techniques were either
introduced or further developed. I do not thing that's what the reader of
this (STAR collaboration) paper is expected to do. So I would recommend at
some places to be more definite. Thus for instance in spherical
decomposition part you should explain which l and m values are
permissible, what is the physical meaning of diffrent coefficient and what is the
reason for their non-monotic behavior (e.g. of A_{22}). You can do it in a
sketchy way but the reader must get the feeling he understands what are
you doing.
The paper has been largely rewritten, and hopefully is more clear. Around Equation (4), we have put some text on what "l" and "m" values are allowed by symmetry, and a little of what they correspond to. Please see if this improves things.
Now specific comments:
1) section 1, paragraph 1, line 13: [6,9,10]. Please add reference to one
of the Richard's papers where the term femtoscopy was introduced. Maybe
even better is his QM2005 talk: R. Lednicky, Nucl. Phys. A 774 (2006) 189.
The same for 6 lines below.
Okay, good idea. It actually appears in the second paragraph, in the present version.
2) section 1, paragraph 2: ... ,in which new phenomenon is not found
replace with: ... ,in which new phenomenon is not expected
Yes, this wording was certainly awkward. The same message, hopefully in a smoother way, is now in the 4th paragraph.
3) section 1, paragraph 3: ..."apples-to-apples"....
Being not a native perhaps I should not complain too much. But I recommend
not to (mis)use this phrase (idiom) too much in the paper. Perhaps you can
use some other word for it, e.g. fair comparison.
Okay. By popular demand, the paper is now fruit-free.
4) section 2, eq. (2): Correlation function defined as well as measured is
a function of 2 varibles - either p_1, p_2 or what is obtained via
orthogonal rotaion (e.i. does not change the Jacobian) q = p_1 - p_2 and k
= p_1 + p_2.
So either you change the definition eq.(1) accordigly or mention that in
eq.(2) you have integrated over k. Otherwise this is not
"apples-to-apples"
relation and you denote with the same letter two differnt objects.
This is a bit of a quibble, but okay in principle it is a good point, thanks. We now explicitly include the subscript for the total pair momentum in Equation (2), to maintain the six-dimensional character of the correlation function, and then say that, following convention, we drop the explicit reference to P from now on.
5) page 2, left column, top: "It has been suggested [19–21] to
construct the correlation..."
I suggest: It has been suggested [19–21] to express the correlation...
Well, the correlation is constructed in those variables. It may then be expressed in spherical harmonics. So, we think "construct" is more appropriate than "express" at this point.
6) page 2, left column, just before the subsection A. Femtoscopic
correlations:
"However, it was experimentally observed ..., clearly seen at large q,..."
What do you mean by large? You can say e.g. q >> 1/R, where R is
characteristic dimension of the source.
We have now quantified large as > 400 MeV/c.
7) The next sentence: "Usually this structure is parameterized
... that contributes in addition to the femtoscopic component C_F(q)"
I suggest: Usually this structure is parameterized
... that modifies in addition to the femtoscopic component C_F(q) at
large q.
Well, these forms contribute everywhere, not just at large q. They may grow with q, but part of the point is that they affect things everywhere. We don't think specifying "at large q" is appropriate. The surrounding wording (near Equation (5)) now is hopefully more smoth.
8) page 2, right column, bottom: "In hadron-hadron or e+e collisions"
-> In hadron-hadron or lepton-lepton collisions
or at least -> "In hadron-hadron or e^+e^- collisions"
Okay thanks. In the introduction (see line 51), we use the term lepton. Elsewhere (e.g. line 197), we have changed all to e^+-e^-.
9) page 3 just before eq.(14): " Another form assumes that non-femtoscopic
correlations contribute only to the two higher moments of the spherical
harmonic"
Which values do you mean. In eq.(14) you are using explicit values of the
spherical harmonics. It seems to me that you use "only to the two lowest
moments" or I'm wrong?
Yes, thanks. It assumes constant contribution to l=2 components only. The text reflects this now.
10) Eq.(16): please put a blank space between M_3 and M_4
okey-dokey
11) page 3, right column, between eq. (18) and (19):
"where m∗ is the mass of a typical particle in the system (for
our pion-dominated system, m∗ ≈m_{\pi}),"
What about the rho meson? Isn't that a typical particle in the system?
Have you tried to see what comes if you plugg in the rho mass?
Well, since it is the restricted phasespace of the final state that we are characterizing, pions are really more appropriate, and the rho we treat rather as an enhancement in the pi-pi cross section. Using a larger mass increases the characteristic "N," so that around the rho mass one would have N~120 or so.
12) page 5, right column, bottom: "that is the energy and momentum
conservation projected on the twoparticle phase-space."
-> that is overall (total) energy and momentum conservation projected on
the twoparticle phase-space.
Yes, we agree that that entire section was awkward, so it has been fully reworded. The message contained there is now explicitly addressed in the new subsection "Parameter Counting" that starts on line 287.
13) page 8, FIG.9 is obsolete. It jsut contains two pairs of values. Why
don't you mention them in a text?
Well, not sure what you mean by "obsolete," but we agree that there are only two datapoints, so that, especially relative to the other crowded plots, there is lots of white space. We are open to removing the figure altogether, but see no harm in keeping it as is. We leave it for now, but if you or others feel strongly, we will remove the figure and just put the numbers in the text.
14) page 11, secon paragraph: "In particular, we observe a significant
positive correlation between the one- and three-dimensional and the
multiplicity of the collision."
-> In particular, we observe a significant positive correlation
between the one- and three-dimensional radii and the multiplicity
of the collision.
D'oh! Thanks.
From Dave Underwood [21 July 2009]:
Here are my comments on the femtoscopy paper (ver 2, July 14) so far:
section 1, paragraph 1, line 6 after RHIC[1-4] it looks like a line is missing in the middle of a sentence and I don't know what it was supposed to say.
Thanks yes, this is hopefully much improved in the present version. Take a look at the first paragraph now.
section 1, paragraph 3, line 5 would read better as
"problematic for two reasons"
We actually mention the two reasons now in the third paragraph of section 1; that paragraph is considerably shorter now and hopefully reads more smoothly. Then, in Section V.B., where we discuss details of comparing to high energy experiments, we get more specific.
section 1, paragraph 4 It may not be obvious to all readers on first reading that "hadronic collisions" refers to no nuclei.
Okay, in lines 51-52, we say "hadron (e.g. p+p) and lepton (e.g. e+e-)..." It looks ok I guess, but maybe there is yet a better way?
section III paragraph 1
the PID technique used in this analysis allows one to reconstruct........
We have reworded that part (see around line 324) to be more specific. In particular "Pions could be identified up to a momentum of 800 MeV/c by correlating..."
section IV. part A
There should be some description of exactly what is being fitted in figures 1 and 2.
The fits of non-femtoscopic correlations in figure 1 look so good that there is no need for femtoscopic fits. Then the femtoscopic fits in figure 2 look very good, but one does not know whether the data selection is different from figure 1 or there is just a subtraction or what.
Oooh, here I guess maybe there is a real confusion. The data and the fits in Figure 1 and 4 (I changed 2-->4, see below) are THE SAME data and fits. It is just a different representation. I have put in an explicit paragraph about this-- see lines 379-390. Please see what you think.
Furthermore, ALL of the fits include femtoscopic correlations. This was not mentioned in the caption to Figure 1, which is probably the root of some confusion. I have added explicitly to Figure 1 "Femtoscopic correlations are parameterized with the form in Eq. 11; different curves represent various parameterizations of non-femtoscopic correlations used in the fit and described in detail in Sec.II.B"
It might also be nice to give non-experts some crude idea of the extent to which kinematic boundaries affect the correlations without their reading all the references. For example, the actual kinematic constraints (energy available per pion) must be a function of multiplicity. How far are these momenta from the limits?
Well, actually the energy available per pion probably does NOT change much with multiplicity! We make this argument in our spectra paper, but one can as well point to the fact that the average pT of pions changes only very little with multiplicity in heavy ion or pp collisions. Nevertheless, the *effect on spectra shape* (and the strength of correlations induced by conservation laws) _does_ vary with multiplicity. Maybe a good example is seen in Figure 12 in our spectra paper http://arxiv.org/abs/0807.3569
An idea of how close any given pion is to the edge of phasespace is probably given by N*<E> from our EMCICs fit. This is 14.3*(0.68 GeV) = 9.7 GeV. Since our midrapidity pions have ~0.5 GeV energy, they are not right at the edge. Do you think it makes sense to discuss this around line 423? I haven't done so, yet, since I'm not sure whether maybe there is a better way. Let's discuss that.
section 4, part B, paragraph 5 bottom of left column
"expected to be approximately twice as large as the radius from..."
Thanks. Please see lines 480-484.
section VI discussion #3 on last page
"halo" not "hallo" ??
Thanks. Fixed. Line 642.
From Debasish Das [4 Sept 2009]
Dear PA and GPC,
interesting analysis!
The abstract re-written:
The two-pion correlation functions from p+p collisions at sqrt_s = 200 GeV is
measured using the STAR detector at RHIC.
The measured correlation lengths (radii) extracted from this analysis in
p+p is
comapared with world dataset of femtoscopic
measurements done with hadron-hadron and e+-e- collisions.
What effects do you think are "surprizingly similar"? Not clear for the
reader.
We think the re-write that you suggest is too short, and does neglect the important issue of non-femtoscopic correlations. However, you suggest to neglect the "surprisingly similar" statement (unless we go into more detail on it). As we think about it, your suggestion makes sense, as this point is something that might unnecessarily cause a sticking point within STAR. This is now removed.
In paper "HBT" and "femtoscopy" are both used at regular intervals. Its
misleading
so needs to have either one of the acronym.
Well, we think both need to be used, for (at least) the following reason. We talk about non-femtoscopic correlations, so we do need to talk about "femtoscopic" correlations and it's natural to refer to femtoscopy then. But the radii we are extracting are traditionally called "HBT radii." It's a somewhat unfortunate term, but it's there, and a point about this paper is that we are making contact with previous analyses, in which the term "HBT radii" and "HBT" are used; there is also the so-called "HBT puzzle," to which we make passing reference. But you are right that we hadn't really made the connection between them explicitly. We have added a statement at lines 25-26, which we hope helps.
Section-I page1
line-6 "and that physics..." sentence incomplete.
Thanks. It is fixed.
Next line: The flow is ---> Flow can be explored in .....
Yes, this part was awkward and actually too brief. It is hopefully better worded in lines 14-21.
Next sentence: "However....." needs to be restructured, now difficult to
understand.
Please see lines 28-35 for a better wording.
So understanding flow using femtoscopy is one of the main if not the only
purpose of
this paper?
No. The purpose is to make a connection between HBT measurements in hadronic ("particle") collision experiments, and in heavy ion collisions. Obviously, we are *presenting* hadronic collisions. The point to mentioning flow etc is to motivate and emphasize the importance of connecting to heavy ions. In particular, we learn more about heavy ions when we understand the pp reference (hence we mention energy loss at high pT). Also, HBT is particularly interesting (i.e. not only energy loss is interesting) because we think it tells us a lot about the underlying bulk dynamics of heavy ion collisions, AND because it has proven itself a sensitive observable in terms of the physics in the models.
Hopefully, this case is made in lines 28-47 and 68-78.
Since the next sentence asserts that "The most direct probe of collective
flow is
...femtoscopy...."??
Well, that statement is true. We word it hopefully more clearly now in lines 28-39.
2nd para, page1:
The motivation now has changed again. It states that we need pp for
baseline only
for Heavy Ions!
Mentions "jets" but none of plots have any "simulation" to show its effect in
femtoscopy?
Why do we need this line at all? Its confusing.
As mentioned above, it was meant to make an analogy to high-pT studies, in which one better understands hard probes (jets, leading particles) in AA when one has a well-understood reference (pp). But you are right, it was worded and placed in a confusing way. The message is now put in a less confusing way around line 75.
3rd para line6:
"....mostly within the particle physics community.....apples- to- apples"
such phrases maybe too informal and needs to be restructured.
Okay. By popular demand, the paper is now fruit-free (no apples).
Next sentence: "Secondly...."---> Hard to understand what it means. Needs
to be
restructured.
Agree. Please see lines 56-60, which are hopefully clearer.
Section-II
Eq1. If these are 4-vectors probably good to use bold. Or else needs to
have vector
sign.
Eq2. Shifts from 4 to 3 vectors, but its confusing. Needs to be explained.
Okay, that makes sense, you are right. We make all three-vectors.
Part A (femtoscopic correlations) page2:
While discussing Lambda we state "mis-nomer" But in next line "we do not
discuss it
further" ? Why?
Well, lambda as you know, usually encodes the percentage of (uncorrelated) contamination from particle mis-id, etc. It is not the point of the paper, and does not affect the HBT radii. So we don't discuss it in this paper. (As we don't on any of STAR's HBT papers, actually. Although soon I think Michal's group will produce a paper in which lambda is important.)
After Eq.9, Page2, right hand column,
"Another femtoscopic effect that affects...." -> difficult to understand,
needs to
be restructured
Right. This was in introduction to Coulomb suppression. Now it appears near line 203, hopefully more smoothly.
Part B(Non-femtoscopic...)
Line3: What is a "standard fit" and why is it "standard"?
As the text says, "standard" fits are those that neglect non-femtoscopic correlations altogether (\Omega=1). We use "standard" only as a term, that's all, to refer to such a fit. (Since we have so many fit forms, we give them names.) "Standard" is also handy, since it implies that this is what most people use (e.g. in STAR).
Last line, same page:
Phrases "ad-hoc" and "physically motivated" needs explanation. Difficult
otherwise.
Here, we actually think the wording is clear as it presently stands, but that's often true from a PA's point of view ;-) Can you suggest an alternative?
Page4:
KT definition incorrect. Correct one here:
http://arxiv.org/abs/0903.1296(Phys. Rev. C 80, 024905 (2009))
Check vector sign-all over the text.
???? but it's the same as in that paper, or? In particular, kT=0.5*|\vec{p}_{T,1}+\vec{p}_{T,2}| Please look again, maybe you misread (or I'm just overlooking something).
Under Fig.1 "blue triangles" and in same page under Fig.2 "red stars" and
"violet
circles" can be misleading if one
take and reads from a print-out where all in black. Correct them for all
medium
online as well as offline(paper mode).
We have modified most figures to make sure that the symbols can be distinguished in black-and-white mode. (i.e. there are no "red triangles" and "blue trianges" on the same plot). There is no problem with saying "red triangles" and "blue squares." The person in black-and-white mode will obviously look for the "squares," not the "blue squares."
But nuts, I now see that we didn't do it for all figures-- there are still ambiguities that would appear in black-and-white. I am going to release the present version and correct this in the next one, okay? I am modifying macros that Zibi gave me, and I don't want to rush; I am slowly implementing these changes now, and with other stuff going on, it probably takes a few days.
Page-8:
Fig9 and Fig10:
They look very different...
I am a little confused. Figures 9 (multiplicity dependence of RG and Rinv) and 10 (mT dependence of Rout, Rside Rlong ratios) are different, so that's why they look that way. Note that in the new draft 2.1, these are Figures 9 and 11.
...and Fig10 is "too loaded" for a non expert reader
to even
understand whats going on.
Make it in two parts.
Fig 10 (11 in the new draft) is the mT dependence of the 3d radii ratios. I agree that there is plenty of data on there, but disagree that it is too loaded. It allows to see the flatness of the ratios, at the same time as the systematics due to different treatment of non-femtoscopic correlations.
One thing I could probably agree is to remove the 50-80% Au+Au points. Would this help, do you think?
Also why is Cu+Cu missing here since in next Figure
we have
Cu+Cu added? Its
very confusing and making more difficult to understand for any reader.
No, come on. Then it would be too loaded, with zero additional information content.
Why
only
Au+Au 200 GeV chosen and not Au+Au 62.4 and
Cu+Cu 200 and 62.4?
Because the point here is to compare p+p to Au+Au with all else constant. So we don't want to change the energy. After all, the first paper from STAR was 130 GeV, and we don't put that on there, either. ;-)
Page9:
Presented results show that the multiplicity is a scaling variable that
drives
geometric the femtoscopic radii at midrapidity.
Because Rout includes both space and time information
the simple scaling with the final state geometry is not expected.
Because of the finite intercepts of the linear scaling
[10, 42], results do not confirm predictions that freeze-out
takes place at the constant density [43].
What does this line mean? Does this not sound contrary to "universal mean
free path at freeze-out"?
We have removed this discussion, as it is besides the main point of the paper.
Page10:
The details mentioned from item1 to item5 are various previous analyses
and models.
How do we relate them to the presented pp data here?
Are they just for mentioning? If so just citation would have been enough,
rest the
references shall speak?
Those items are proposed (usually without numerical predictions) physics mechanisms which might be behind the pT-dependence of the HBT radii. We said at the beginning motivation that the pT-dependence could be interesting, so we have measured it and presented it, and these items make sense for the discussion, as possible physics. For each, we give reasons that they could or could not be plausible.
Page11:
Discussion:
"This is crucial, since in the later case, the pT systematics have
provided the most
compelling evidence for collective flow in heavy ion collisions"
Not clear, this is known,
Well, it's been pointed out many many times in the literature.
Nevertheless, we have removed this sentence, as it might cause hold-ups in the collaboration as a whole. It might appear in a separate follow-up publication.
so what way is this new for pp and how to make
an inference?
We won't make an inference here. That might show up in a separate follow-up publication.
Dave Underwood [12 December 2009]
I like version 2.1. It is a major improvement.
The only big problem I see is that as far as I can tell, there is no definition
of MT but it is in the discussion extensively after line 418.
Thanks for catching this.
We have changed the sentence (now in line 427)
"The $m_T$-dependence of the radii in all cases is quite similar."
-->
"The dependence of the radii on $m_T\equiv\sqrt{k_T^2+m^2}$ is quite similar in all cases."
Should it be obvious in Eqn 5 why coulomb is multiplicative rather than addative?
I havn't thought about this or gotten to the references yet.
It is a fair question. In principle, in using the Koonin-Pratt equation, one
convolutes with the square of the wavefunction in relative coordinates. In this
case it should be the symmetrized Coulomb wavefunction, or better said, Coulomb-distorted
symmetrized plane wavefunction. It turns out that, for sources smaller than the Bohr radius (good for heavy
ion collisions and very good for pp collisions), one can instead use symmetrized plane waves
times unsymmetrized Coulomb. The reason to make this approximation is the convenient
fitting function that results, for Gaussian sources.
This is discussed for example in our review paper (Reference 11); see around Equation 10 in
that paper.
While it is a good question, my own feeling is not to discuss it explicitly in our
paper, as it really is a settled detail in the HBT procedure and not one we study in our
paper.
The conclusions don't come across as strong as the introduction.
Yes, I agree with this statement. I think what we have here is a presentation of
the data. The introduction tried to motivate that this data is generically important
but drawing conclusions at this point is difficult.
I make no secret of MY conclusion from this data (that pp collisions generate strong
flow), but it is likewise no secret that STAR is actively hostile to this conclusion.
However I choose to respect the right of STAR to subscribe to a view,
so am willing to leave these important results open to speculation (in the "discussion"
section). Maybe a later paper will go more into the physics. (OK, not "maybe"...)
There are a few typos
line 28 systmem
line 105 explicity
line 268 eqn needs a j
Thanks, they are fixed. Good catch on the "j."
Michal Sumbera [13 December 2009]
This version, how could it be the other way after so long elapsed form the
previous one, represent substantial improvement.
Here are my, somehow scattered, comments on version 2.1:
1. Reading fresh a new I found too many "correlations" in it. In some
sentences it apperas 4 times. I suggest from time to time use the other
word like effects e.g. in abstract
"... the presence of strong non-femtoscopic effects."
Yes, I see what you are saying. The word "correlation" shows up
a LOT. It is somewhat unavoidable in a paper like this. The word itself
appears 126 times in version 2.1!!!
Using a thesaurus for "correlation" yields the following:
connection, association, link, tie-in, tie-up, relation, relationship,
interrelationship, interdependence, interaction, interconnection; correspondence, parallel.
Not really promising. Your suggestion of "effect" can be used in some places
(like the one you suggest), but that word is really much more vague.
Firstly, we have to accept that this is a paper about correlation functions,
that we discuss femtoscopic and non-femtoscopic correlations, not to be confused
with space-momentum correlations that are very different but *probed by* two-pion
momentum correlations!
But okay I agree. I have gone through the paper in detail, and tried to avoid
saying "correlation" too soon after using the word previously. I think you should
find it better now. Section II.B. is probably the worst offender, but it is better
than it was.
"Correlation" is now mentioned "only" 85 times in version 2.2, and it usually
is not repeated too close together, like it was in version 2.1. Anyway, it should
be better, take a look.
2. line 119: It has been suggested [25-27] to express..." I'm not quite
sure if we construct the 3d-correlation function this way.
But, we do. Probably I don't understand your point. This will be a good thing to discuss
by evo meeting.
3. equations (7), (8) and tables I -IV: Consider to change the subscript
of the radii R_G etc from capitals to lower case i.e. R_G -> R_g. The
reason being that you are using (o,s,l) also in the lower case.
Well, now that you bring it up, we are using "O,S,L" often in *upper* case in
Table headings, and (as you mention in #5 below) sometimes "out" instead of "o"
as a subscript.
I agree that we need to standardize. "o,s,l" (lower case) are the industry standard,
so I will change all - in text - to that. R_G (not R_g) is more the standard, so I will
leave "G" in upper case.
We will need to standardize the figures as well as the text. Since we have this
update of the figures pending (so that all symbols are distinguishable in black-and-white),
this standardization will occur simultaneously with that. This I am asking Zibi to do,
so will do that after tomorrow's meeting.
4. Eq.(14): would'n it improve the readability to include in the first
line (or replace on the secon one) expression 1+\beta Y_{2,0}+\ksi
Y_{2,2}. It's a long time ago when some people heard about the wave
function of hydrogen atom...
Okay, we have done this, thanks.
5. Fig.1: Change C(q_{out}) -> C(q_{o}) as well as q_side -> q_s and
q_long -> q_l.
Yes, thanks. We will do this simultaneously with the figure upgrade.
6. Line 279-280:
"...and consider whether their values make physical sense." ->
"...and consider whether their values are mutually compatible and physical."
Good, thanks.
7.Line 385: "... is based on the desire to represent" -> "...is based on
determination to represent..."
okay, changed.
8. lines 433-436:
"Although three-dimensional correlation functions encode
more information about the homogeneity region than do
one-dimensional correlation functions, most previous particle
physics experiments have constructed and analyzed the latter."
->
"Since three-dimensional correlation functions encode
more information about the homogeneity region than do
one-dimensional correlation functions, they are also more statistics
hungry. So most of the previous particle physics experiments have
constructed and analyzed the latter."
Umm, okay, I like your wording better, so it is changed. However, as we both know, 3D correlation functions
are not really that much more statistics hungry than 1D ones, a bit counter-intiutively.
9. When discussing energy-momentum conservation in pp I have not found in
the article any word about inelasticity of the collision. Its know for
long that pp (especially) does not provide the best fireball. For the
later antiproton-proton annihilation where inelasticity is 1 are
excellent. When scanning the literature, ahve you guys run into ANY
corresponding HBT data?
We have had a few more email exchanges on this, after you wrote up these comments.
I think we should discuss this more on the evo meeting.
10.Lines 708-9: I do not think that conservation law-driven effects are
problematic. What they may be is that they may show up less. So I suggest
wording:
"At the Large Hadron Collider, similar comparisons will be possible, and
the much higher energies available will render conservation law-driven
effects less important."
That sounds good, thanks.
11. Last but not least I still don't like your Fig.9 with too few points
to deserve their presentation in thsi way. What about turning Figs. 8 and
8 into a single figure with different left and right scales?
Well, I don't like the left and right scales things-- too many different
radii and colors.
How about a compromise? How about we combine Figures 8 and 9, such
that they share a common x-axis (dN/deta), but there is an upper panel (currently
Figure 8) and a lower one (currently Figure 9). Does this make sense?
Let's talk about that at our evo meeting. I won't change it for now until we talk.
Comments from our phone meeting of 17 Dec 2009 (minutes by Mike):
Hello GPC,
Thanks for meeting today. It appears that our chairman got disconnected at the end, but I'm glad we could touch base and I think we were about finished anyhow.
Here is what I took away from our discussion today. Let me know if I missed anything and I'll put a summary onto the web page.
* Paul was satisfied. He did make the comment that we could mention pp earlier in the introduction, which is probably a good comment. I will take a look at this.
We have added a paragraph at the very beginning of the Introduction, that we hope brings the pp focus of the paper to the beginning. We still go into heavy ions immediately afterwards, however, since it is crucial for the motivation of this analysis.
* Michal was overall happy with the analysis and with the paper, with some further discussion:
- at the end, he wants that we mention that EMCICs will be less important at LHC due to high multiplicity, not just high energy.
[Insertion] Michal later followed up by email with the following suggestion for the final sentence:
"Similar, qualitatively better comparisons will be possible at the Large
Hadron Collider. The much higher incident proton energies will not only
render the conservation less problematic but also give access to
correlation analyses in several multiplicity bins allowing thus to study
EMCIC weakening directly."
Well, I don't like "qualitatively better comparisons at LHC." Come on, this is a STAR paper. LHC measures collisions at TeV scale and above, and we measure at 200 GeV. Our meausrements are very nice. We can, ourselves, come back with higher-stats measurement, to make it QUANTitatively better. I do not want to advertise that LHC will do "better" measurements. Putting LHC as an "outlook" is fine; it is only natural, and that's why we did it in the first place. But let's not go too far.
Also, I thought that you didn't like the word "problematic"?! I had used "problematic" originally, but in your comment #10 to the version 2.1, you wanted to use "important" instead, which I agree is better, so I changed it to "important" in v2.2.
Also, I want to point out that in our paper we have seen EMCICs decrease with multiplicity. See e.g. Table VIII. But okay, I agree this will be interesting at LHC.
OK, here's what I've done for v2.3:
"Similar comparisons will be possible at the Large Hadron Collider, where the higher collision energies will render conservation laws less important, especially for selections on the very highest-multiplicity collisions."
- we discussed some more about the CPLEAR p-pbar annihilation-at-rest HBT data. If I understand correctly, we agreed at the end that the CPLEAR data really has no relevance to be discussed in our paper.
- he urged us to use darker colors as we tweak the figures. We will try to do this.
- it wasn't entirely clear that he was 100% happy with my proposed compromise to combine figures 8 and 9, but he was willing to leave it to me and the journal editors ;-)
* Dave didn't bring any new big issues beyond the ones he raised in the previous two iterations, but he wanted a chance to go through everything one more time.
* Tomasz said he didn't have any huge issues, but wanted to collect his comments together over the weekend and send them by Monday.
Tomasz sent a follow-up email, to which we respond below.
* Debasish couldn't join us, but sent a short mail saying that he is satisfied with the draft and our responses to his earlier detailed comments.
Now, Michal stressed that publication of our paper is "urgent," given the imminent release of LHC data. I actually agree with this (having seen said data), but I do NOT want to RUSH this paper through, plowing over any actual concerns. So, the only thing to take away is a request to identify any remaining issues on reasonably short timescale, but do NOT hesitate to identify something serious that needs work. Although some papers do proceed in "emergency panic" state in STAR, that is really not the right way to go.
It is up to Michal and overall GPC to make the determination, but it seems to me that we are about ready to go. I think we agreed that folks should take a look at the paper again over the weekend, to see whether there is a major issue we have not yet identified. If it turns out that there is not, but only small wording issues that can be handled very quickly, then I will probably ask Michal to make the call and send it on to Bedanga.
Comments from Michal Sumbera sent 21 Dec 2009
1. line 134: second-order oscillation about the "long" direction
-> second-order deformation around the "long" direction
???? No, this is not right. Why "deformed?" We will replace "about" with "around," but the correlation function oscillates, it is not deformed.
2. line 137: R_{out} and R_{side} -> R_{o and R_{s}
Oops, thanks. I'd thought I'd caught all of those on the previous iteration
3. line 205-6: ... wavefunction integradted over the source .
-> wave function integrated over the source emission points.
Okay thanks.
4.line 224: q -> $q$
Thanks.
5. Equation (14): put first two expressions onto one line (yielding
two-line expression instead of three-line)
Well, actually, Zibi made the good point that we should explicitly indicate that the spherical harmonic functions depend on angle, so now it really has to be on three lines. The formula doesn't format so beautifully even after I've screwed around, I do admit, but this really is something for the editor.
6. line 259: phasespace -> phase space
Okay thanks.
Comments from Tomasz Pawlak sent 22 Dec 2009
1. Line 120: do we need definition of theta and phi angles?
Well, I don't think so. The "out," "side," and "long" Cartesian directions were defined in previous paragraph, so I think the expressions in Equation (3) are, in fact, the definitions of those angles theta and phi. I mean, I could also right that theta=arccos(sqrt(q_{o}^2+q_{s}^2)/q_{l}), but this really is redundant with Equation (3).
2. Line 295: "other fits" - what abuot references?
Okay thanks. We have added a citation to Brown (2005) about the spline fits, and to Kittel:2001 and Kittel:2005 (a book together with De Wolf) on the others.
3. Figure 1: Correlation functions are not normalized. Is normalization parameter N fitted?
Yes, as shown in the fitting function in equation (5) and also mentioned in the second paragraph of Section II.C, the normalization N is an explicit fit parameter. We generally do not list its value in the tables, or plot its value, as it is not of physical interest.
4. Table VI: deltaQinv - maybe better \delta_sup{Q_sup{inv}} ?
Ah thanks, good catch! It should actually be simply \delta. Fixed now.
Many of the changes going from version 2.2 to 2.3 were in response to GPC comments. Several more were small tweaks to figures (colors, symbols) that had been discussed. A few more came up in the final polishing process. Any change not in direct response to a GPC comment is recorded here.
Now, several small changes in figures, mostly axes labels and captions, along with color tweaks.