Behaviour of the quark number densities as

In CC reactions we are now in a region where rn so the formulae (16.4.27) etc. greatly simplify. One has, to a very high degree of accuracy  

The only error in the above comes from neglecting the KM matrix elements Vtd and Vis, which sure of order 10 , compared with unity. We are assuming that there is no top production even at these values of Q. When in fact top is produced then obvious modifications must be made to (16.4.27) etc. near the threshold for top production, and (16.5.4) and (16.5.5) become exact well beyond the threshold. 

Because of their connection with virtual photon nucleon scattering, the behaviour of the structure functions Wi 2 in the high energy limit of that process, i.e. oo, with fixed, should be given by Regge theory (Abarbanel, Goldberger and Treiman, 1969) as 

If the form (16.6.1) continues to hold as 00, i.e. in the scaling region, then to get scaling we need, for large Q,  

In particular, the leading (Pomeron) contribution would suggest 

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