Re: [Brahms-l] paper on K/pi at 62 GeV AuAu

From: Peter Christiansen <peter.christiansen_at_hep.lu.se>
Date: Fri, 13 Mar 2009 14:21:49 +0100 (CET)
Hi,

I did not have time yet to read the full paper in detail, but I have some
general comments on some parts (particularly the data).

If I sound a bit sour then add a few smileys:-) I know that this
represents a great amount of work! However, I feel that with a small
effort on the data part (and a little work on the text) this could be a
really great paper!

So here I go:-)

The quality of the data is not impressive. y=-0.1 and y=0.1 gives quite
large differences: 202 vs 215 and 208 vs 216. As this is where we have the
easiest analysis it is a bit worrisome.

In general the dN/dy trend between 0 and 1 is at best flat, but more looks
rising?!. I would appreciate to see the data points for the integrated
yields (no fits!), i.e., from pT 0.35-1.8 for pions where there is
coverage for all 4 data points. (and the same for Kaons:0.35-1.90). If
that shows the same trend, then ok..... One could also as an additional
check overlay the spectra (Ian's idea).
My personal feeling is looking at fig1 that the two low pT data points at
y~0 is much below the fit.

This is important for my main point which is that it is a bit sad for me
that there is no follow up on the Landau story which I like, but ok, the
Gauss fit is not so good if dN/dy(y=0) <= dN/dy(y=1).
Should the provoking conclusion be: pion dN/dy is Gaussian at SPS/AGS and
RHIC maximum energy but not at 62 Gev?

How can URQMD give any meaningful contribution to the ratio discussion
after you killed it in Fig. 2? I agree that the trends in Fig. 4 is much
better, but then you should perhaps rescale the URQMD pions?

A lot of times the p/p-bar is used, but no reference is given (as far as I
can see).

Table 1 and 2. Could we have the y-range. F.R. is for what fits? (there is
quite a large difference between power law and mt). Maybe we should just
give the yields in the pT-range.
Is the point at 3.32 meaningful to include? 8% coverage!
In general I would reduced the numbers to e.g. 202+-3

Summary:
which is understood -> which is not understood. Seriously!

What is the main message of this paper? IMO it should be that the particle
ratios exhibits a universal behavior from SPS top energies to RHIC top
energies as a function of p-bar/p e.g. figure 5 and 6. While this can be
partly understood in the statistical model with a constant T (why do we
not compare to those models, e.g. therminator/Michael Murray) the rapidity
dependence can only be understood if we have local equilibration in y i.e.
the particle production at rapidity y is dominated by the chemical
potential at rapidity y.

Not only does the event generators fail to describe the specific energy
dependence, but:
a) AMPT shows no universal behavior (figure 6)
b) the associated production of K+ relative to pi+ at large baryon
chemical potentials (low p-bar/p) has the opposite behavior in both models
as in the data (figure 5)

My prioritized wish list:-)
1) Data consistency check at y=0 and y=0+1
2) Add a Gaussian fit to figure 2 and mention Landau
3) Update summary
4) Add the therminator/statistical model curves on the plots

Cheers,
   Peter



On Fri, March 6, 2009 1:16 pm, flemming videbaek wrote:
>
>
>
> Dear Collaborator,
>
> The paper "\title{Kaon and pion production in central Au+Au collisions
> at $\sqrt{s_{NN}}=62.4$~GeV} has been prepared by Ionut Arsene,
> and reviewed discussed among a fairly large group including the
> committee members JH, Pawel, Dieter, Trine. It has also been discussed
> extensively in the
> weekly analysis meeting. The paper is intended to be submitted to
> Physics Letters B.
> It is now ready for collaboration review; I would appreciate comments
> within the next two weeks with a deadline of Friday March 20.
> Hopefully it can be submitted before QM 2008.
>
>
> best regards
> Flemming
>
>
>
>
> Flemming videbaek
> videbaek @ bnl.gov
> Brookhaven National Lab
> 631-344-4106
> cell: 631-681-1596
>
>
>
> _______________________________________________
> Brahms-l mailing list
> Brahms-l_at_lists.bnl.gov
> https://lists.bnl.gov/mailman/listinfo/brahms-l
>


-- 
Peter Christiansen
Email: peter.christiansen_at_hep.lu.se
Phone: (+46) 046-2227709

Address:
Lund University
Department of Physics
Div. of Experimental High-Energy Physics
Box 118
SE-221 00 Lund
Sweden

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Received on Fri Mar 13 2009 - 09:24:57 EDT

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