Λ and
Round 1
Reviewer 1 Report
- Rows 10, 11, as well as 38 – a clearer specification of the fact that STAR data and predictions for NICA energy range are considered in this paper
- Row 27 – nucleus collisions or nuclear collisions or nuclei collision
- Row 30, 31 – HADES Collaboration results – more details in text, considering the differences between experimental results and predictions for anti-lambda (Table I)?
- Row 53, 54 – motivation of the rapidity selection for spectators: a clarification of the selection manner for collisions at different energies seems to be necessary
- Row 68 – motivation for the energy density in the fireball; it is specific for the final state, at freeze-out?
It seems to be specific to other nuclear matter phase (liquid-vapor, probably)
- Rows 75-82 – the explanation of the time selection must be improved. It is related to the general evolution of the fireball or to the vorticity kinematics? Are these values of the evolution time specific for the given impact parameter of the two colliding gold nuclei at the given energuy or ar used at other energies and impact parametres, too? Why?
- Rows 107-110 – There are some remarks that can confusing the reader. The autors consider the time of the last interactions and present evolution in a time range 0-20 Fm/c. In the same time an afirmation related to the freely stream towrds the detector is introduced. It seems that the particles are registred in detctor in very short times, almost the same order with the selected time range.
- Table I increases the confusion in the selection of the parameters mentioned above, having two energies. The good results for lambda and the large difference for anti-lambda seem me unexplained clearly.
- An explation could help in the acceptation of the disussion on Fig.5 (rows 160-169), where are melt results form 3 GeV per nucleon in CMS, to 200 GeV per nucleon in CMS.
Author Response
1) We change the sentence at lines 38-40
2) line 27 we replace with "nucleus-nucleus collisions"
3) In this work we consider only two collision energies - 7.7 and 11.5\,GeV. The HADES results are mentioned just in passing. The problem with its description can be clearly seen in Fig.3 of the HADES publication. We added a remark in the manuscript. We add a comment that calculation in Ref. [22] by Vitiuk et al describes the Lambda polarization at the HADES energy.
4) The spectator nucleon is identified if its rapidity does not change from the beam rapidity by more than the rapidity of the nucleon Fermi motion, which is about 0.27 for the atomic nucleus density of 0.16/fm^3. The comment is added in line 56.
5) This condition is not used as a condition of particles freeze-out. Evolution of each particle is traced till all interactions cease.
It is used only to decide if the cell contains enough particle that we can assign a particular value of thermal vorticity. Thereby we avoid unphysically large gradients temperature occurring on the fireball boundary. We add the comment on line 71.
6) The time in the code is counted from the moment of nuclei initialization. Then there is a short time of approach and the interpenetrating time.
The first time moment we show corresponds to the maximum overlap. Two later times are chosen for the best illustration of the structures created in the velocity and vorticity fields.
7) Time of the last interaction is a characteristic of each particle among the test particles, which distributions are evolving during the transport code. It fixes its last interaction, after it propagates towards detectors. This propagation takes as much time as it needed, but the particle will not interact anymore. For collision at 7.7 GeV main part of interaction ceases at t=15-16 fm/c. However, there are still contribution from resonance decays which are Lorentz-delayed. We changed text in lines 109-117.
8) We have not influence the running of the code and adjusted any parameter to get the hyperon polarization. Merely, we fixed the points wherefrom the hyperons goes to the detector and calculated the vorticity field around this point formed by participant-nucleons. Many details fluidization and structure of created fields are given in Ref. [25].
9) In the discussion it is clearly stated that the linear increase of polarization as that we see in our calculations was observed at various energies. The director comparison of our current calculations is possible only with the results of STAR at the energy 7.2 GeV. We used our calculations at 7.7 GeV and imposes the same momentum and rapidity cuts as in Ref [44], the results are presented in Fig. 5 (right panel) in comparison with experimental data.
Reviewer 2 Report
The paper contains valuable study on the Lambda global polarization in heavy ion collisions with PHSD model. The authors evaluated the global polarization of Lambdas caused by vorticity field and did a comprehensive study in terms of centrality dependence. I recommended it to be published in Particles after considering some minors comments.
1) Figures captions, e. g. Fig. 1 and 2, please use complete sentences instead of phrases.
2) Fig. 1 and 2: The colors in the figures are all yellow-red: the contrast is not strong enough. Probably one can use blue-red to make it clearer.
3) Fig. 4: please enlarge the figure.
4) Fig. 5: full stop missed.
5) Is it possible to add one figure including a direct comparison to the STAR data?
6) Although I am not a native speaker of English, I feel that the English of the article can be improved.
Author Response
We appreciate the positive decision of the Reviewer about our manuscript and thank for constructive comments and suggestions.
We made the following modification in the manuscript
1) Caption of Figs 1 and 2 are changed.
2) We try our best in selection of various color schemes to present the generated vector field. Using more contrast scheme like a blue-red one makes the figure unreadable since the dark color overwhelms the lighter one. There less contrast scheme preferable therefore. With the reviewers permission we would like to keep colors in Figs. 1 and 2.
3) Fig. 4 is made bigger
4) Fig. 5: the sentence is finished.
5) We include direct comparison of our calculations at 7.7 GeV with the experimental data for collisions with the energy 7.2 GeV.
The same momentum and rapidity cuts are imposed.
6) We make an effort to control spelling and grammar of the manuscript.
