Charm in Deep Inelastic Scattering

We outline the existing descriptions of the charm component of the deep inelastic proton structure function F2. We discuss recent approaches to include charm mass effects in the parton evolution equations and the coefficient functions. Contribution to the Proceedings of the Madrid low x Workshop, June 18-21 1997, Miraflores, Spain Both H1 and ZEUS have used c → D to measure charm production in the HERA domain [1]. They find F c 2/F2 ∼ 25%, as compared to the EMC measurement of F c 2/Fc ∼ 1% at lower fixed-target energies. Moreover, the precision of the measurements of F c 2 (x,Q ) will improve, particularly when vertex detectors become available. Such measurements should reveal important information on the gluon, which enters at LO through the photon-gluon fusion (PGF) process γg → cc. Clearly it is important to see how best to include the charm mass effects in the analysis. At NLO we have