Re: [Brahms-l] comments to pp paper

     Dear JJ,
           the protons at y=0 are mainly produced in pairs with  
antiprotons and so pbar/p is close to 1.0 . However at y=3 pbar/p is  
very small and this implies that most of the baryon number must be  
transported from the beam rapidity.
Michael

On Jan 12, 2007, at 4:13 PM, Jens Jørgen Gaardhøje wrote:

> Dear Michael,
> You say that pQCD reproduces mesons and pbar wel , but not p.  That  
> may be one one the logical links we are searching for, for the  
> physics discussion in this paper. That is to my recollection not  
> stated in the paper. Rather we see a model reproducing p+pbar  
> wonderfully, a pbar spectrum no one attempts to describe and yet  
> negative statements about the AKK variant.
> Now, I can follow your surmise that something is amiss with the  
> proton, if indeed only the p's are not reproduced, however, why do  
> things work at y=0 but not at y=3. Surely its tougher to move some  
> fractional baryons all the way from y=5.6 to y=0 than just to y=3 (?).
> cheers
> and goodnight
> 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.
> ______________________________________________________________________ 
> ___
> ----- Original Message -----
> From: Michael Murray
> To: brahms-l_at_lists.bnl.gov
> Sent: Friday, January 12, 2007 5:33 PM
> Subject: 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.
>> _____________________________________________________________________ 
>> ____
>> _______________________________________________
>> Brahms-l mailing list
>> Brahms-l_at_lists.bnl.gov
>> http://lists.bnl.gov/mailman/listinfo/brahms-l
>
>
>
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