Measurement and Phenomenology of the Proton Structure Function F2 from Zeus at Hera

Measurements of the proton structure function F2 in the Q range 0.6 − 17 GeV from ZEUS 1995 shifted vertex data and Q ≃ 1.5 − 20000 GeV from 1996 and 1997 ZEUS data are presented. From the former and other ZEUS F2 data the slopes dF2/d lnQ at fixed x and dF2/d ln(1/x) at fixed Q are derived. F2 data at Q below 0.9 GeV are described successfully by a combination of generalised vector meson dominance and Regge theory. Using a NLO QCD fit the gluon density in the proton is extracted in the range 3× 10 < x < 0.7 from ZEUS 1994 and 1995 data. For Q ∼ 1 GeV it is found that the qq̄ sea distribution is still rising at small x whereas the gluon distribution id strongly suppressed. It is shown that these observations may be understood from the behaviour of the F2 and dF2/d lnQ data themselves.