Re: [Brahms-l] comments to pp paper

>

      Dear JJ,
            I think that the most interesting part of the paper is  
that current models of QCD cannot reproduce the number of high pT  
protons at y=3 while they can do a good job for the mesons and pbars.  
This suggests to me that either we don't understand the distribution  
of low x partons inside the proton or that the models fail in how  
they move baryon number from the beam rapidity to y=3.

Michael

>
> Now here I come to my prob. more serious comments.
>
> I find the comparison of data to the two pQCD sets  (mKKP and AKK)  
> confusing and the statements unclear.
>
> What I understand to be the case is that:
> 1) mKKP can reproduce the meson data well, but cannot calculate the  
> baryons (?) or does not reproduce the baryons (?).
> 2) AKK can do the total p+pbar and agrees with STAR data  at y=0.  
> From the plot in the paper it obviously reproduces our total p+pbar  
> data. So from that I would assume that AKK is a wonderful model.
> 3) There is some unexplained issue related to the AKK physics that  
> led you to distrust the meaning of the AKK set (?)
>
> There seems to be some logical link missing here. What is the point  
> you are trying to make.?
>
> I suppose that what you are tying to say is that AKK does not -at  
> the same time as reproducing the total - reproduce the pbar/p  
> ratios and therefore the agreement with the data must be  
> 'accidental'. This is not demonstrated to the reader.
>
> The issue is therefore not clear. What is the exp. surprise? That  
> there are many high pt protons? I somehow lack a demonstration that  
> this is not expected from theory. The shown curves do not evidence  
> that- on the contray : all fits well.
> Finally, the issue of the charge ratios (p/pi) being different is  
> not taken up in the comparison to theory. So why is this  
> surprising?. Earlier on you say that you expect soft p spectra. Is  
> this clear from pQCD? AKK does, as you show, reproduce the total p 
> +pbar spectrum.
>
> In summary I find that the main physics points of the paper are  
> unclear.
>
> If you can outline the reasoning to me in an email I will try to  
> express it as a paragraph for discussion --- I have to make amends  
> for being so late with these comments.
>
> cheers
> JJ
>
>
>
> ______________________________________________________________________ 
> ___
> Jens Jørgen Gaardhøje, Professor, Dr. Sc.
> Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark.
> Tlf: (+45) 35 32 53 09, secr. (+45) 35 32 52 09, Fax: (+45) 35 32  
> 50 16.
> UNESCO Natl. Comm.: secr. (+45) 33 92 52 16.
> Email: gardhoje_at_nbi.dk.
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