Origin of the Q
2-dependence of the DIS structure functions |
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Authors: | B I Ermolaev M Greco S I Troyan |
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Institution: | 17313. Ioffe Physico-Technical Institute, 194021, St. Petersburg, Russia 27313. Department of Physics and INFN, University Rome III, Rome, Italy 37313. St. Petersburg Institute of Nuclear Physics, 188300, Gatchina, Russia
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Abstract: | We consider in detail Q 2-dependence of the DIS structure functions. Very often this dependence is claimed to be originated by the Q 2-dependence of the QCD coupling. This leads to the small-x asymptotics of the structure functions with Q 2-dependent intercepts. We demonstrate that the DGLAP parametrization α s = α s (Q 2) is an approximation valid in the region of large x (where 2pq can be approximated by Q 2) only, providing the factorization scale is also large. Outside this region, the DGLAP parametrization fails, so α s should be replaced by an effective coupling which is independent of Q 2 at small x. As a consequence, intercepts of the structure functions are independent of Q 2 . Nevertheless, the small-x asymptotics of the structure functions explicitly depend on Q 2 , even when the coupling does not depend on it. We also consider the structure functions at small Q 2 and give a comment on power-Q 2 corrections to the structure functions at large and small Q 2 . |
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