Longitudinal and transverse structure functions of proton and deuteron   at large x
  Higher-twist effects in the low-order moments of the longitudinal and transverse structure functions of proton and deuteron have been analyzed using available phenomenological fits of existing data in the Q**2 range between 1 and 20 (GeV/c)**2. Both twist-4 and twist-6 contributions have been determined adopting the Natchmann definition of moments, which allows to disentangle properly target-mass effects. The extraction of the matrix elements of the relevant twist-4 operators, describing quark-quark and quark-gluon correlations, is carried out in case of the second moment. The need of transverse data with better quality for x > 0.5 and Q**2 < 10 (GeV/c)**2 as well as more precise and systematic determinations of the L/T separation make JLab @ 12 GeV a good place to improve our understanding of the non-perturbative structure of hadrons. 
G. Ricco and S. Simula