  We show that recent data from HERA on the proton structure function $F_2$ at
small $x$ and large $Q^2$ provide a direct confirmation of the double
asymptotic scaling prediction of perturbative QCD. A linear rise of $\ln F_2$
with the scaling variable $\sigma$ is observed throughout the kinematic region
probed at HERA, and the measured slope is in excellent agreement with the QCD
prediction. This provides a direct determination of the leading coefficient of
the beta function. At large values of the scaling variable $\rho$ the data
display a small but statistically significant scaling violation.

High Energy Physics - Phenomenology;High Energy Physics - Experiment