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References - Bogoliubov Laboratory of Theoretical Physics - JINR

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α eff<br />

s<br />

= αs(μ 2 )+ 1<br />

� �<br />

arctan<br />

πb<br />

= αs(μ 2 )+ 1<br />

πb<br />

�<br />

arctan<br />

π<br />

ln(k 2 ⊥ /βΛ2 )<br />

�<br />

�<br />

πbαs(k 2 ⊥ /β)<br />

where β is the faction <strong>of</strong> the longitudinal moment. When<br />

α eff<br />

s<br />

�<br />

− arctan<br />

can be approximated by the much simpler expression:<br />

If additionally x is large, α eff<br />

s<br />

π<br />

ln(μ 2 /Λ 2 )<br />

��<br />

� �<br />

− arctan πbαs(μ 2 ��<br />

)<br />

(3)<br />

μ 2 ≫ Λ 2 e π ≈ 23Λ 2 , (4)<br />

α eff<br />

s ≈ αs(k 2 ⊥ /β). (5)<br />

≈ αs(k2 ⊥ ). Therefore, the QCD coupling in the Standard<br />

Approach is always μ -dependent, though implicitly, through Eq. (4).<br />

3 The μ -dependence <strong>of</strong> g1 at small x<br />

The μ -dependence <strong>of</strong> g1 at small x is even more involved because accounting for contributions<br />

∼ ln n (1/x) requires to change the DGLAP-ordering by the new one:<br />

μ 2

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