Experimental moments of the nucleon structure function F2

✍ Scribed by M. Osipenko; W. Melnitchouk; S. Simula; S. Kulagin; G. Ricco

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 206 KB
• Volume: 174
• Category: Article
• ISSN: 0920-5632
• DOI: 10.1016/j.nuclphysbps.2007.08.079

✦ Synopsis

The difference between NLO and NNLO is small with respect to uncertainties of the data 2 ,

(1)

where LT n is the leading, twist-2 moment, α S is the running coupling constant, μ 2 is an arbitrary scale (taken to be 10 (GeV/c) 2 ), a τ n is the matrix element of corresponding QCD operators, γ τ n is the anomalous dimension and τ is the order of the twist.

The separation of the LT from the complete series is to some extent dependent on the order to which one calculates the LT Q 2 -evolution. In Fig. 1 we compare the n = 8 moment of the LT term calculated at fixed orders in pQCD: Leading Order (LO), Next-to-Leading Order (NLO) and Next-to-Next-to-Leading Order (NNLO); and by using resummation of soft gluon emission (SGR) [2]: Leading Log (LL) and Nextto-Leading Log (NLL). The fixed order calculations appear to converge at NLO 1 . However, at fixed pQCD order the logarithmic precision of the LT term deteriorates the closer one gets to x = 1. Applying the SGR [2] we can improve the accuracy of the LT term in the large-x region. The