Re: [Brahms-l] A short comment on stopping models

Hi,

I could understand from talking with Dieter that my email could be 
misunderstood in the way that something was incorrect in the NA49 talk. I 
don't think so.

The point was merely that one should (as always) be careful about saying 
that something is trivial because it can be described (usually 
aftwards:-) by a model.

About Ians comment, my suggestion would be that Flemming (if he haven't 
already done so) contacts the authors and let them know of our concerns.

It is nice that they want to use our data, but better if they use the 
actual data:-)

Cheers,
    Peter

On Wed, 22 Nov 2006, Peter H.L. Christiansen wrote:

> Hi,
>
> At QM NA49 has shown some comparisons to UrQMD calculations that seems 
> to reproduce the trends seen in rapidity loss, see the parallel talk by 
> C. Blume.
>
> This is in my opinion a postdiction and one argument for why it is not 
> always a good idea to quote postdictions by models as real 
> understanding is to look at the paper:
> Baryon junction loops and the baryon-meson anomaly at high energies
> Phys. Rev. C 70, 064906 (2004) (11 pages)
>
> If you look at Figure 6 in the paper you will see that all the model 
> calculations describe the data perfect, but if you look at the data 
> they have used and compare to our data you will see that their 
> net-baryons at y=0 are around 10 while ours are around 15. They have 
> misunderstood the correction we mention *2/3 to get feeddown corrected 
> protons and *2 to get net-baryons, BUT NOT BOTH AT THE SAME TIME!
>
> So their model can apparently pretty much describe everything.... and 
> maybe they should have thought a little bit more about the huge 
> disagreement they get with our energyloss calculation on the page 
> before even though the fit curves looks similar to their model curves!
>
> I mentioned this to Flemming one year ago and was surprised that not 
> everybody in BRAHMS knew about this. I think it is an important point, 
> because you clearly see that model calculations needs a lot of 
> (correct:-) data to be constrained.
>
> Cheers,
>   Peter
>
> :-) --------------------------- )-:
> Peter H L Christiansen
> :-D --------------------------- \-:
>

:-) --------------------------- )-:
  Peter H L Christiansen
  pchristi_at_nbi.dk / (+41)764870425
:-D --------------------------- \-:
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