Re: Ratios Paper - Draft 2.2

From: Michael Murray (murray@CyclotronMail.tamu.edu)
Date: Tue Jun 25 2002 - 14:57:55 EDT

  • Next message: Jens Jørgen Gaardhøje: "Re: Ratios Paper - Draft 2.2" 

         Dear Claus and Jens Jorgen,
                       thanks for the new ratios draft. I think
that it is a great improvement. However I have some concerns
about Fig 4, I have attached my version.
 The first is that the thermal curve for Becattini is wrong.
>From PRC64 024901 one gets k+/k-=1.17 for pbar/p =0.4. 
That gives k-/k+=0.85 at pbar/p=0.4 in good aggreement with our
data. This is the dashed line in my plot.

Secondly I think it is crucial that we address the question of
weather we have local 
strangeness neutrallity at different rapidities. If this were 
so as long as the temperature does vary mu_s (and hence k-/k+)
is  fixed for a  given mu_b (ie pbar/p). Therefore we should
see a universal curve of k-/k+ versus pbar/p. In my plots I have
shown our 130GeV data and pp data from (Alper et al). They
are both in good agggreement with our 200GeV data. 

Third all k-/k+ data lie above (pbar/p)**1/3. Thus we have
a positive mu_s which approches 0 as pbar/p goes to 1. 

Finally I would prefer to use the published NA44 pbar/p ratios
rather than the QM99 pbar/p values from NA49. The spokesman of
NA49 told me that he thought the pbar yields should go down.
This would bring there pbar/p closer to ours. Both experiments
aggree on k-/k+.

AMPT does not reproduce the data, both k-/k+ and pbar/p are 
too high. In my plots the yellow  band shows AMPT for the same
rapidity region as our data. Also the Pt slopes are not quite
the  same were as for us our ratios have no Pt dependence.

Masashi has found that feed-down from weak decays does not 
effect the k-/k+ or pbar/p ratios very much. This strengens
our case for using them in a thermal analysis.   
 
For my plot I guess errors of 10% for the pp data. Tess is typing
in the spectra for me so that I can  get the proper errors.
The k-/k+ ratio E866 is at y=0 and would be somewhat lower if
averaged over the same region as the pbars, ie 1.0<y<2.2.
 

In summary it seems that a thermal description of our data
with T~160-170MeV and local strangeness neutrallity gives 
a good  description of our data. K-/k+ vs pbar/p looks like 
a universal curve.

Michael Murray, Cyclotron TAMU, 979 845 1411 x 273, Fax 1899
    kmpvpbarp.gif

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