ar X iv : h ep - p h / 06 10 04 3 v 1 4 O ct 2 00 6 Experimental moments of the nucleon structure function F 2

Experimental data on the F2 structure functions of the proton and deuteron, including recent results from CLAS at Jefferson Lab, have been used to construct their n ≤ 12 moments. A comprehensive analysis of the moments in terms of the operator product expansion has been performed to separate the moments into leading and higher twist contributions. Particular attention was paid to the issue of nuclear corrections in the deuteron, when extracting the neutron moments from data. The difference between the proton and neutron moments was compared directly with lattice QCD simulations. Combining leading twist moments of the neutron and proton we found the d/u ratio at x → 1 approaching 0, although the precision of the data did not allow to exclude the 1/5 value. The higher twist components of the proton and neutron moments suggest that multi-parton correlations are isospin independent. The Operator Product Expansion (OPE) is a powerful tool in QCD which allows measurable moments of hadronic structure functions to be related to series expansions of the moments in terms of twists. The first term in the series, corresponding to Leading Twist (LT), reflects the physics of asymptotic freedom, and is determined by single-parton distributions in the hadron. Subsequent terms in the series, or Higher Twists (HT), describe interactions between partons, or multi-parton correlations. The determination of the HTs is considerably more challenging, both experimentally and theoretically. We analyzed data on experimentally extracted moments of the proton and deuteron structure functions F 2 [1] to separate LT and HT terms.