BFKL evolution can be enhanced by studying DIS events which contain an identified jet of longitudinal momentum fraction xjet=pz(j)/Eproton (in the proton direction) which is large compared to Bjorken x [42]. By tagging a forward jet with this allows minimal phase space for DGLAP evolution while the condition leaves BFKL evolution active. This leads to the forward jet production cross section in BFKL dynamics being larger than that of the QCD calculation with DGLAP evolution [43].
In Fig. 8, recent data from H1 [44] and ZEUS [45] are compared with BFKL predictions [46] and fixed order QCD predictions as calculated with the MEPJET [17] program at NLO. The conditions and are satisfied in the two experiments by slightly different selection cuts. H1 selects events with a forward jet of pT(j)>3.5 GeV (in the angular region ) with
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Fig. 8 shows that both experiments observe substantially more forward jet events than expected from NLO QCD. A very rough estimate of the uncertainty of the NLO calculation is provided by the two dotted lines, which correspond to variations by a factor 10 of the renormalisation and factorisation scales and .A recent BFKL calculation (dashed lines) gives a better agreement with the data. The overall normalisation in this calculation is uncertain and the agreement may be fortuitous, indeed it should also be noted that both experiments observe more centrally produced dijet events than predicted by the NLO QCD calculations. Further careful investigation is necessary before claiming that BFKL is the mechanism for this enhanced forward jet production.
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