The role of FL(x, Q2) in parton analyses

We investigate the effect of the structure function F-L in global parton analyses of deep inelastic and related hard scattering data. We perform NLO and NNLO analyses which include the reduced cross-section HERA data at high y, as well as earlier direct measurements of F-L. We find that the NNLO analysis gives a better description of F-L at low x than that performed at NLO. Nevertheless the data show evidence of the need of further contributions to F-L, which may be of higher-twist origin. We study such corrections both phenomenologically and theoretically via a renormalon approach. The higher-twist corrections extracted from a successful fit to the data are in general agreement with the theoretical expectations, but there is still room for alternative theoretical contributions, particularly at low x and Q(2). The importance of future measurements of F-L is emphasized. (c) 2006 Elsevier B.V. All fights reserved.