Photon structure functions: Are they measurable?

It is shown that 3 of the 8 independent photon structure functions are simply calculable using leading logarithm techniques in QCD. We then discuss which of these are most readily measurable in the processese ⁺e^?→e⁺e^?+X,γp→μ ⁺ μ ^? X andμp→μμ ⁺ μμ ^? X. Detailed predictions are given for the latter processes including the case where beam and target are longitudinally polarised. Given sufficient beam intensities, the contributions from the anomalous (as opposed to vector meson-like) component of the photon structure function would be easily identifiable above the Bethe-Heitler pair production background. However, currently available beam intensities make such measurements impractical at present. We discuss simple algorithms for estimating the polarised and unpolarised quark and gluon distributions inside the proton and the hadronic (?-like) piece of the photon.