> Dear Nu and Zhangbu, > > The comments from TAMU are below. > > Best regards, > Saskia > > ----------------------------------------------------------------------------------------------------------------- > > Overall, we thought the paper was well written. With some modifications, we think it will be a "slam dunk". > > A general comment is that the connection between the theoretical effect and the measurement is not obvious to a non-expert. This is not the fault of the PA's, but the nature of the measurement. Exchanging paragraphs 4 and 5 may help in the introduction of the measurement. > PAs: The paragraph 3 introduces the observable with some related concepts like reaction plane, while paragraph 5 is already into technical discussions of why we use such an observable, and para 5 is closely followed by the details of the event plane. We'd like to keep the introduction simple, and leave mathmetics in later sections. > Abstract: Make it less explicit about what STAR has previously measured (since Cu+Cu and 62 GeV measurements are not included). > PAs: The text in the abstract has been changed to: "for heavy-ion collisions at the top RHIC energies" > Introduction: > Second sentence: provide -> provides PAs: Done. > Two suggestions to help motivate the measurement. > - why beam-energy dependence is interesting > - what are alternative interpretations (in these "intense discussions") > PAs: A sentence has been added to para 2: "A study of the beam energy dependence of the charge separation will shed light on the interpretation of the data." Other interpretations or backgrounds were discussed in the later part of the paper. > Fig. 1 ¨C suggestions: overlap region ¨C could be just an ellipsoid shape (without the individual nucleons) and spectator colors could be (red and blue) to denote red shifted and blue shifted to indicate directions. > PAs: We doubt that readers can really link the color with red/blue shift, which takes some imagination. We opt to keep the current scheme, with the caption clearly mentioning the directions. > Data sets: > Which 62.4 GeV data set was used? > 62.4 GeV Au+Au data cannot be from 2005, as the paper states. 2004 data had fewer than 8M events, 2010 data had much more. > If it¡¯s 2010 data, a comment about consistency with previous publication should be added. > > Why not mention the previous publication of 62 GeV data (and Cu+Cu data) in the introduction? > PAs: The 62.4 GeV data were from run4. We explained this in Sec 3.1 of the analysis note: https://drupal.star.bnl.gov/STAR/system/files/Analysis%20note%20for%20LPV%40BES.pdf > Figure 2: > MEVSIM should be a line in the legend and include line types for like sign and unlike sign. PAs: fixed, and a sentence is added in the caption. > Boxes (systematic errors) too light (better in fig 4). > Legend: labels symbols as gamma_OS and gamma_SS > Then in caption ¡°The opposite-charge correlations are shown with open circles and a dotted line, and same-sign correlations with stars and a dashed-dotted line." > PAs: We followed the convention of our previous publications, which seems to be well received. > Why not discuss results from FTPC for the reaction-plane > determination? They were included in the BES just for this > purpose. Also, in the previous papers, the FTPC played a significant > role in estimating the systematic uncertainties associated with the > determination of the reaction plane, which as this paper notes is a > dominant uncertainty. Without the FTPC (or ZDC-SMD), this paper > gives no indication how that systematic has been evaluated for these > BES measurements. (Note that it is certainly not fair to assume the > reaction plane determination systematic is energy independent. So > you can't just take it from the previous study.) > PAs: FTPC was operating in part of run10 and run11. But if you read STAR v2@BES papers, you won't find v2{FTPC} there. There were no FTPCs in 19.6 and 7.7 GeV. You can only find one FTPC track every 100 events at 39 GeV. At 11.5 and 27 GeV, there are on average 3 tracks from each FTPC, about 10 times fewer than nominial. And there are FTPC holes at 11.5 GeV. In short, FTPC is not usable during BES. The consistency between event planes from TPC, FTPC and ZDC-SMD at 200 GeV showed that the observable is well-constructed, with the traditional "non-flow" largely canceled out. We don't see why lower energies should significantly change the feature of this observable. On the other hand, we plan to study this effect with the new event plane detector in the future BES II. > The difference (of gamma_OS and gamma_SS) discussed on page 5 is not explicitly displayed. > If PA's don't want to add another set of data points for the difference on Figure 2, relabeling of symbols (as mentioned above)to gamma_OS and gamma_SS would help reader more easily see it is just the difference of the two curves. > PAs: Once the paper is published, the data points will be accessible to public, and people, if interested, can do the subtraction themselves. Moreover, gamma presents signal+bg, and delta presents bg, so H in Fig 4 is more meaningful. Also, you can find gamma_OS - gamma_SS in Fig 13 of the analysis note. > Page 5: between equations (4) and (5) mentions the detector acceptance effect on kappa. Detector acceptance effects should be corrected for! Any effect not possible to correct for should be in the systematic errors. > PAs: With a detector of |eta|<1, how can you obtain the knowlege in the full eta range? This is not an efficiency that can be "corrected". kappa relies on such information beyond our acceptance, and that's why it's uncertain. More discussions can be found in Sec 3.6 of the analysis note. > Discussion of Fig. 4: downward trend toward LHC data point should be addressed. What is a possible explanation for this? > PAs: There may be reasons like the duration time of the magnetic field. But we don't want to rush to any explanation here since a comparison betweeen different experiments requires better understanding of their systematics (not there yet for LHC). Even the data point for 60-80% is missing. We want to avoid such conclusion until more information is aquired. > Conclusion doesn¡¯t include any other possible interpretation. > Phrase ¡°if we increase statistics by ten times¡± should be removed. 1) It makes the current results sound less important and 2) systematic errors (due to other present physics correlations) are in many cases larger than the statistical. > PAs: Other possible interpretations rely on how small the signal is at 7.7 GeV, which requires 10 times more statistics. > Ref. 15 ¨C 021301 should be 012301. > PAs: Done.