Proton and deuteron F2 structure function at low Q2

Measurements of the proton and deuteron F-2 structure functions are presented. The data, taken at Jefferson Lab Hall C, span the four-momentum transfer range 0.06 < Q(2) < 2.8 GeV2 and Bjorken x values from 0.009 to 0.45, thus extending the knowledge of F-2 to low values of Q(2) at low x. Next-to-next-to-leading-order calculations using recent parton distribution functions start to deviate from the data for Q(2) < 2 GeV2 at the low and high x values. Down to the lowest value of Q(2), the structure function is in good agreement with a parametrization of F-2 based on data that have been taken at much higher values of Q(2) or much lower values of x, and which are constrained by data at the photon point. The ratio of the deuteron and proton structure functions at low x remains well described by a logarithmic dependence on Q(2) at low Q(2).