Re: [Brahms-l] meson paper

Hi Djamel

(and anyone else on the list).
Some of the issue that are raised in the points to a discussion we have had
several times w/o coming to a conclusion.
Do our data in dn/dy support Bjoerken or not? \
Taken at face value with the syst errors (point to point)
I will tend to agree with Dieter that the y<1 are consistent both with being
flat (Bjoerken like) as also the Star data in similar rapidity ranage says,
but is also consistent with a near Gaussian.
This tells me that we should not focus on the part of the data where it is
hard and difficult to say anything clearcut;
 (albeit anyone can certainly promote either in talks) but should focus on
the overall dependence as the paper the paper
does so nicely. This is our strong point as also said in the second par of
the paper.

Some comments to the comments by Dieter.

par 1)
Chemical composition.. I is certainly true that Chem comp. cannot prove
equilibration, but could also come from mainly
phase-space dominance (Koch)- it is albeit a necessary condition. I think
the introduction should give general arguments
why it is important to measure particle abundances (after all this is why we
designe Brahms). It is a tool in this sense for both therm. models as well
for dynamical models to get this right.
page 2)
feed-down correction? has anyone done this ? I know that for the dn/deta the
pions from k0s decay are essentailly counnted, and will suspect that the pi
from Lambda are not due to vertex cuts , but w/o a detailled MC it is not
known.

Figure 2.
The caption say the curves are fit to the data. Which one has been plotted
G1,G2 or WS? (as ref I would ask this question). I assume it is either G2 or
WS since the fit to fig 3 which is a Gaussian is slightly off;
The point for Fig 3 is of course it is a Gaussian with Landau values and
therefore in my opinion worth to keep even if the data are the same Just
showing sigma's would not convey the message as strongly.


the 72% question:
I think that it in fact impossible from inclusive distribution to determine
if the scenario is 'transparency' or ' near full stopping+longitudinal
expansion' . As is
implied in the paper most of the 72% do in fact end up
in long. energy. At eta=-1,1 only about .5*600*1.5*2 GeV == 900 GeV ~1 TeV
out of a total of 350*.72*200== 50TeV is present in the final state;

I would think it serves the paper best just to state at end that it is
consistent with Landau and leave out the
(fairly obvious ) reservations about other possibilities. They have been
(and should be) qualified in the main text before
then.

regards
    Flemming

PS excuse my sometimes missing 'd''s due to my keyboard




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

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



>
> Dear Djamel,
>
> my comments. Most of them are a repetition of what I have sent around
> earlier within the paper comittee.
>
>
> Abstract:
> Why did you remove our numerical results? Now the abstract contains no
> information at all.
>
> P.1, first par.:
> remove "The chemical composition (abundances) of
> the produced particles constitute an important tool to
> test if equilibrium occurs in the course of the collision."
>
> The statement is wrong. See the discussion at QM'02 in Nantes,
> chaired by Koch. Elliptic flow might prove equilibrium; but not
> particle ratios.
>
>
> p2, second par.:
>
> be more specific about the amount of particles from
> Lambda and K0 decays. This is important in order to use our data
> for thermal model fits.
>
> p3, figure 3:
>
> exchange figure with inset. The figure itself contains no new information
> in addition to fig.2 and eqn. 1.
>
>
> p3, second column, 2. par:
>
> The statement
> "As mentioned, collisions at RHIC
> are neither fully stopped nor fully transparent, although
> a relatively high degree of transparency is observed [3]
> corresponding to an average rapidity loss of the colliding
> hadrons of about y 2.2."
>
> contradicts the statement (same page)
> "The analysis of nuclear stopping in central Au+Au collisions at
> psNN = 200 GeV [3] has demonstrated that about 72%
> of the participant energy is lost during the collision and
> potentially available for particle production, ..."
>
> I would not call 72% stopping a "relatively high degree of transparency".
> Remove the sentence.
>
>
> p3, second column, 2. par.:
>
> remove: "The fact that the obs. dist. are flatter at mid-rapidity and
> wider ...may point in this direction."
>
> Don't try to educate the PRL reader that a wider Gaussian is automatically
> flatter around y0. That's the whole point of a Gaussian.
>
> p4, sec. colummn, last par.:
>
> remove
> "although the overall width and the behaviout of the distr.
> around mid-rapidity suggest increased longitudinal expansion at
> RHIC energies reminiscent of the Bjorken picture."
>
> The distributions are Gaussian, punktum. Small deviations
> can easily be explained by our contaminations from weak decays.
> There is no "behaviour around mid-rapidity".
>
> What is an "increased longitudinal expansion"??
> This makes no sense.
>
>
> With best wishes,
> Dieter
>
>
>
> On Fri, 5 Mar 2004, Djamel Ouerdane wrote:
>
> > Hi,
> >
> > You can find the latest draft of the meson paper here:
> >
> > http://www.nbi.dk/~ouerdane/mesonAuAu.ps
> > http://www.nbi.dk/~ouerdane/mesonAuAu.pdf
> > http://www.nbi.dk/~ouerdane/mesonAuAu.tex
> >
> > or you can get it from CVS:
> >
> > cvs -d /afs/rhic/brahms/BRAHMS_CVS co papers/mesonAuAu200
> >
> >
> > The plan is to make an announcement soon, and submit it next Friday.
> > Please make final comments and corrections so that we can do it as I
> > mentioned.
> >
> > Thanks,
> > Djam
> >
> >
> >
>
> -- 
> --------------------------------------------------------------------
> Dieter Roehrich                   |
> Institutt for fysikk og teknologi | Email: Dieter.Rohrich@ift.uib.no
> Universitetet i Bergen            |               Tel: +47-555-82722
> Allegt. 55                        |               Fax: +47-555-89440
> N-5007 Bergen, Norway             |    http://www.ift.uib.no/~dieter
>
>
>
>
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