Leading and higher twists in proton, neutron and deuteron unpolarized structure functions F2
Sezione di Roma 3, Istituto Nazionale di Fisica Nucleare, Via della Vasca Navale 84, I-00146, Roma, Italy
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Accepted: 30 November 2006
Published online: 9 March 2007
We summarize the results of a recent global analysis of proton and deuteron F2 structure function world data performed over a large range of kinematics, including recent measurements done at JLab with the CLAS detector. From these data the lowest moments (n≤10) of the unpolarized structure functions are determined with good statistics and systematics. The Q2 evolution of the extracted moments is analyzed in terms of an OPE-based twist expansion, taking into account soft-gluon effects at large x. A clean separation among the leading- and higher-twist terms is achieved. By combining proton and deuteron measurements the lowest moments of the neutron F2 structure function are determined and its leading-twist term is extracted. Particular attention is paid to nuclear effects in the deuteron, which become increasingly important for the higher moments. Our results for the non-singlet, isovector (p-n) combination of the leading-twist moments are used to test recent lattice simulations. We also determine the lowest few moments of the higher-twist contributions, and find these to be approximately isospin independent, suggesting the possible dominance of ud correlations over uu and dd in the nucleon.
PACS: 13.60.Hb Total and inclusive cross sections (including deep-inelastic processes) – / 12.38.Cy Summation of perturbation theory – / 12.38.Qk Experimental tests – / 12.38.Lg Other nonperturbative calculations –
© Società Italiana di Fisica and Springer-Verlag, 2007