Observation of scaling of the photon structure functionF2γat lowQ2

The structure function $F_2^{\gamma }$ for a quasireal photon has been measured in the reaction ee→eeX for $Q^2$ in the range 0.2<$Q^2$<7 ${\mathrm{GeV}}^2$, by use of 9200 multihadron events obtained with the TPC/Two-Gamma detector at the SLAC storage ring PEP. The data have been corrected for detector effects by a regularized unfolding procedure and are presented as $F_2^{\gamma }$(x,$Q^2$). The structure function shows scaling in the region 0.3<$Q^2$<1.6 ${\mathrm{GeV}}^2$, x<0.3, and rises for higher $Q^2$ and x>0.1. Below $Q^2$=0.3 ${\mathrm{GeV}}^2$, scaling breaks down in accordance with the finite cross-section bound for real photons.