[Brahms-l] meson paper - referee report

Dear collaborator,

We have just received a response from PRL on the meson paper. It seems we are being unlucky with referee's not responding,
but the one report says it is well suited for PRL, with some questions and comments. Djamel and the writting commitee will prepare a response
an hopefully we can re-submit shortly

flemming

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Subject: Your_manuscript LQ9562 Bearden

Re: LQ9562
    Charged meson rapidity distributions in central Au+Au collisions
    at $sqrt s sub {NN}$=200 GeV
    by I.G. Bearden, D. Beavis, C. Besliu, B. Budick, H. Boggild, et al.

Dr. D. Ouerdane
Niels Bohr Institute
Blegdamsvej 17
DK-2100 Copenhagen, DENMARK

Dear Dr. Ouerdane,

The above manuscript has been reviewed by one of our referees.  We ask you
to consider the enclosed comments from the report.

While we cannot make a definite commitment, the probable course of
action if you choose to resubmit is indicated below.

( ) Acceptance, if the editors can judge that all or most of the
    criticism has been met.

(X) Return to the previous referee A for review if available.

(X) Submittal to new referee(s) for review.

Please accompany any resubmittal by a summary of the changes made, and
a brief response to all recommendations and criticisms.

Yours sincerely,

Christopher Wesselborg
Senior Assistant Editor
Physical Review Letters
Email: prl@aps.org
Fax: 631-591-4141
http://prl.aps.org/

P.S. Another referee was consulted but we now assume that no report will
     be received. If a useful report is received, we will contact you.


--------------------------------------------------------------------
Report of Referee A (LQ9562 Bearden,I)
--------------------------------------------------------------------

The manuscript is well written and the data presented by the BRAHMS
collaboration are sound and of high significance. A unique feature of the
BRAHMS experiment, compared to the other experiments at RHIC, is the
possibility to measure identified particles over a large region of the
longitudinal phase space. Therefore these data have a high relevance to
current physics discussions in this field.

In the manuscript basically two issues are addressed. One is the question
of how strangeness production evolves as a function of the beam energy and
as a function of the measured phase space region. Especially the phase
space dependence of the particle ratios is of importance for the
comparison to statistical model predictions.

The second issue is related to the shape of the measured rapidity
distributions. Here the key point is whether there is room for a boost
invariant region at central rapidities, or whether the discussed Landau
scenario is more relevant. This topic has been discussed decades ago for
proton-proton reactions, but has been largely disregarded in the
discussion of heavy ion reactions. The spectra presented here will
therefore have a large impact on the interpretation of high energy heavy
ion reactions.

Therefore I would consider the manuscript well suited for publication in
Physical Review Letters. However, I have a couple of comments and
questions that the authors should address:

As stated in the text, the extrapolation of the pt/mt-spectra is done
using a power law fit to the pt-spectra and an exponential fit to the
mt-spectra. Since these extrapolations are not equivalent they will result
in different results and presumably this difference constitutes a part of
the systematic error quoted for dN/dy. Here, I would like to ask the
authors to be more precise on the determination of the systematic error.
Also, it would be helpful to state in the caption of Fig. 1 whether the
dashed lines correspond to the exponential (as one would conclude from the
text, since the figure shows mt spectra) or the power law fit.

Even though it is clear from the appearance of Fig. 2, I would recommend
to reformulate the first sentence of the caption, e.g. like: "Pion and
kaon rapidity densities (a) and their mean transverse momentum <pT> (b) as
a function of rapidity."

The values on <pT> shown in Fig. 2 and the values given in the text are
without systematical error. Since the calculation of <pT> can be strongly
dependent on the way the pt-spectra are extrapolated into the unmeasured
regions, the systematical error can be substantial and also rapidity
dependent. Therefore, I would suggest to include a statement on the
systematical error of <pT> and its dependence on rapidity in the text,
similar to what is discussed for the extracted dN/dy values.

The K/pi ratio as a function of rapidity, as shown in Fig. 3(b), clearly
exhibits a difference between K+/pi+ and K-/pi-. As the authors explain,
this can be attributed to an increase of the baryon density at forward
rapidities. However, this will also increase the feed-down contribution to
the pi- spectra, since the Lambdas approximately will follow the
net-baryon distribution. The authors state that all spectra shown are not
corrected for feed-down from hyperon decays, therefore the decrease of the
K-/pi- ratio at forward rapidities can to certain extend be caused by
this. So, in order to substantiate the conclusion drawn from this figure,
I would like to ask the authors, whether they have any estimate of the
magnitude of the feed-down contribution and its rapidity dependence.
Ideally, a full correction to the data should be applied, but in any case
the possible influence of the missing correction to the data points in
Fig. 3(b) should be discussed in the text.

----------------------------------------------------------------
Flemming Videbaek
Physics Department
Brookhaven National Laboratory

e-mail: videbaek@bnl.gov
phone: 631-344-4106



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