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

Hi all,
As I mentioned to Peter at QM, I think that we should respond to  
this.  I suppose the best way is to write a comment
on the Phys. Rev. C article.  I don't know, though, if this should be  
a "BRAHMS" comment, or if it should be me (and whoever else might be  
interested).
Cheers,
Ian
On 22/11/2006, at 11:24, 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 --------------------------- \-:
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>

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