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TH Meeting on Particle Physics Phenomenology
Total resummation of ln(x) vs. standard description of the polarized DIS
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Europe/Zurich
TH Auditorium (CERN)
TH Auditorium
CERN
Description
The standard theoretical instrument for studying the polarized DIS is DGLAP. When applied to calculating the spin structure function g1, it accounts for logarithms of Q2 to all orders in αs but lacks the total resummation of ln x. Such a resummation provides g1 with a steep rise at small x and leads to the conclusion that DGLAP should not have worked at x < 0.01. However it is known that DGLAP works successfully at the small-x region. The reason is that the standard fits for the initial parton densities include the phenomenological factors which are becoming singular when x -> 0. These factors mimic the impact of the total resummation of ln x and also ensure the power-like rise of g1 at small x. The total resummation of ln x allows us to drop these factors and leads to remarkable simplifications of the fits.
On the other hand, DGLAP expressions for anomalous dimensions and coefficient functions include terms absent in our formulae. These terms are not so important at small x but quite essential when x is large. Combining DGLAP with our approach leads to the description of the polarized DIS equally good at large and small x without using singular terms in the fits.
On the other hand, DGLAP expressions for anomalous dimensions and coefficient functions include terms absent in our formulae. These terms are not so important at small x but quite essential when x is large. Combining DGLAP with our approach leads to the description of the polarized DIS equally good at large and small x without using singular terms in the fits.