Transparencies pdf - Desy
Transparencies pdf - Desy
Transparencies pdf - Desy
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(P gg ⊗ g) / g<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
-0.2<br />
-0.4<br />
10 -8<br />
gluon = CTEQ6M<br />
Q = 2.0 GeV<br />
10 -7<br />
10 -6<br />
10 -5<br />
10 -4<br />
x<br />
10 -3<br />
LO DGLAP<br />
NLO DGLAP<br />
NNLO DGLAP<br />
NLL B (n f =4) Scaling violation for gluons at<br />
small x<br />
- from G.Salam study<br />
10 -2<br />
Current studies of the perturbative QCD lead to expectation that the growth of the parton densities<br />
predicted by LO DGLAP is weakly modified when NLO is included and the attempt to sum various extra<br />
terms does not modify result noticeably down to smallest x relevant for GZK.<br />
Can we trust pQCD prediction that the growth persist down to very small x?<br />
Depends on transverse size of the system. As we argued above - in<br />
practical situation answer is NO !!! already in the region where log x<br />
effects are moderate and could be accounted for by NLO<br />
33<br />
10 -1<br />
10 0<br />
33
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