Abstract :
Recently the H1 collaboration has published a “determination” of the structure function FL(x,Q2) at low x. I address the question of how reliable this determination really is. I argue that it is in fact a consistency check of a given theoretical approach rather than a real determination of the value of FL(x,Q2), but potentially a very useful one. I compare the consistency of different approaches, and indeed find that a LO-in-αs calculation of structure functions is completely ruled out. I also find that the “determined” values of FL(x,Q2) are surprisingly stable under changes in theoretical approach but, when working consistently within a well-defined theoretical framework, the values of FL(x,Q2) implied are somewhat lower than previously quoted.
