Heavy-Ion Collisions at FAIR-NICA Energies
Round 1
Reviewer 1 Report
This is a comprehensive survey on the physics opportunities to be addressed at the upcoming new accelerator facilities FAIR and NICA. The focus is on the state-of-the-art of our knowledge and capabilities to fill the remaining knowledge gaps by the planned experiments. Relations to the big questions in the field are well highlighted.
I recommend the publication of this paper.
A short list of formulation issues or typos includes:
l.15: "a" --> "at"
l.38: "physic" --> "physics"
l.39: "were" --> "will be"
l.73: "the energy range between CBM and STAR --> "the energy range accessible by CBM and STAR"
l.77: missing ")"
l.85: "the mass and radius" --> "the mass-radius relation"
l.88, l.351: "phase transition" --> "transition"
l.127: it looks like a contradiction: one observable favors the soft EOS, another one the hard EOS --> reformulate!
l.143: is this an original figure by the author? if not, add the source!
l.152: "the E_sym" --> "E_sym"
l.154: "ratio, which differ in isospin" --> "ratio, which contains components with different isospin projections"
l.171: "speculations" --> "conjectures"
l.174: explain "132 + 3 - 6 MeV" or write it in a different manner!
l.180: attribute the symbols of T, mu_B, mu_I to the names of these quantities in the fig.5 caption!
l.183: I would prefer "chemical" --> "hadro-chemical" (at many places too)
l.186: unify mu_b vs. mu_B
l.205: add "below the red line"
l.214, l.217, l.219: use "luminocity" with proper units (not "Hz")!
l.223: "at FAIR and NICA" --> "accessible at FAIR and NICA"
l.240: add "within the experimentally accessible range"
l.246: when speaking on "yields" one needs additionally the volume parameter!
l.246, l.348: "(anti-hyperons)" --> "(anti-) hyperons"
l.271: rephrase the sentence's middle part, e.g. "such as the ones implemented in the Hadron_String-Dynamics"
l.291: I would say "challenge the proposed signal of deconfinement"
l.302: "This illustrated" --> "This is illustrated"
l.305: what is "4-pi spectral function"?
l.339: central collisions of which nuclei?
l.361: "A key observable of a 1^st order phase transition are lepton pairs" --> "A key observable of a first-order phase transition is provided by lepton pairs"
l.363: "to discover or to exclude the caloric curve of QCD matter" --> "to discover or to exclude a caloric curve which is specific for QCD matter" (the author should be aware of missing first-principle knowledge of this curve due to the sign problem)
l.365: to my knowledge, 3-body YNN, YYN can be also studied in high-multiplicity pp ... AA collisions at LHC, as follow-up of previous YY and YN interactions via correlations; the author may consider including arXiv:2002.09223 as modern citation, also w.r.t. neutron stars.
Ref. [23] is incomplete, [25, 40] mess up bf-print of volumes and years, in [43] the doi is not needed; I would omit at many places the comma in sentences as in l.28, l.43, l.131, l.211, l.311, and in l.43, l.44 insert a ":" instead of ",".
There are many abbreviations (the author should check whether they are carefully defined; may be a glossary at the end would be useful for the broad audience)
Author Response
I would like to thank the reviewer for the careful reading of the manuscript and for his comments and suggestions, which have been taken into account. Some answers and explanations from my side to the reviewer:
Line 127: the interpretation of the data is not conclusive, and results in a large uncertainty.
Line 143: the figure was made by the author
Line183: "baryon-chemical" potential is routinely used in literature as one axis of the QCD phase diagram
Line 246: particle yield per collision is the synonym for particle multiplicity per collision
Line 365: in high-multiplicity pp, pA and AA collisions so far only two-body correlation functions have been studied.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This is a review about the prospects of two laboratories under
construction, which are going to perform heavy-ion collisions.
It is relatively short, but it captures the important points,
and the author is certainly an expert in this field. It is kept
rather superficial, without going into details, which is probably
intended. The text is in general reasonably well formulated -
exceptions are listed below.
I would have hoped that the article includes some original
elements or lines of thought, but this does not seem
to be the case. In this respect, it is a bit disappointing,
it summarizes some facts, which are well-known in the corresponding
community, and even the figures are adopted from elsewhere.
Nevertheless, it provides a good overview, and perhaps the
original point is that it encompasses two different laboratories.
Now I go though some details, in chronological order, and I
indicate the line number in each case.
L15: Typo: "at neutron star core densities"
L77: the author forgot to close the parentheses.
L82: "governed by same the high-density equation-of-state"
L91: "properties of high-density QCD matter"
L99: The text refers to "the symmetry energy", so it should specify
what symmetry this is about. It refers to isospin symmetry, I suppose.
L121 and 127: The author should specify what he means by "soft EOS".
Up to what energy is it "soft", and what does it mean for the EOS?
Vice versa: when is the EOS "hard", as mentioned in L145.
L131, L211, L217, L219, L311
no comma in front of "that"
L154: What ratio is this? This should be formulated carefully, and
also the continuation: these are two hyperons, which differ in isospin.
L165: The author wrote: "The QCD phase diagram is sketched in figure 5..."
It is important to point out that this is a hypothetical QCD phase
diagram. The same comment refers to the caption, L180.
L192: repeats a statement of L174. If the author insists in the
repetition, he should at least add something like "as we mentioned
before".
L209: referring to the "number of constituent quarks" does not make
much sense - these objects are not well-defined anyhow. I assume that
the sentence was meant to refer to valence quarks.
L210: Should it be "(m_T - m_0)/n_q" ?
L266 and below: I really hope that the final version will have a proper
symbol for "c-bar", and I strongly recommend the use of LaTex.
The same for "anti-D" in L272 and below, and again for lambda
in L323 and below.
L276: "as illustrated in"
L278-280: The statement of this sentence is not clear, perhaps it
should be "..., because in a hadronic scenario..."
L394/5: "... matter as it is created in heavy-ion collisions,
since they carry ..."
L302: "This is illustrated"
L312: should "integrate" be "include"?
L314: no comma behind "possibility"
L348: The formulation "of multi-strange (anti-hyperons)." is strange,
please clarify.
L361: "first order"
L362: "allows us to"
L434: The format of this reference is inconsistent:
remove the word "volume", then "2018, 561".
Once these points are fixed, I think that this article can
be published in Particles.
Author Response
I would like to thank the reviewer for the carefull reading and the comments, which all have been included and marked as red in the revised manuncript, where also the suggestions of the other reviewer are included and marked in red.
One comment to line 210: the lower cases correspond to n_q, for example.
Author Response File: Author Response.docx
