The new FL measurement from HERA and the dipole model

From the new measurement of FL at HERA we derive fixed-Q2 averages 〈FL/F2〉. We compare these with bounds which are rigorous in the framework of the standard dipole picture. The bounds are sharpened by including information on the charm structure function F2(c). Within the experimental errors the bounds are respected by the data. But for 3.5GeV2⩽Q2⩽20GeV2 the central values of the data are close to and in some cases even above the bounds. Data on FL/F2 significantly exceeding the bounds would rule out the standard dipole picture at these kinematic points. We discuss, furthermore, how data respecting the bounds but coming close to them can give information on questions like colour transparency, saturation and the dependencies of the dipole-proton cross section on the energy and the dipole size.