An observation on F2 at low χ

A simple parametrisation of H1 and ZEUS data at HERA is given for the ranges in χ and Q2 of 10−4–5 · 10−2 and 5–250 GeV2, respectively. This empirical expression is based on a strikingly similar dependence of the average charged particle multiplicity 〈n〉 on the centre of mass system energy s in e+e− collisions on the one hand, and the χ dependence of the proton structure function F2 as measured at small χ on the other hand. To the best of our knowledge, this similarity has not been noted before.