ZEUS Results on the Measurement and Phenomenology of $F_2$ at Low x and Low Q^2

ZEUS Collaboration

Paper

ZEUS Results on the Measurement and Phenomenology of $F_2$ at Low x and Low Q^2

Abstract

Measurements of the proton structure function

for

and

from ZEUS 1995 shifted vertex data are presented. From ZEUS

data the slopes

at fixed

and

for

at fixed

are derived. For the latter E665 data are also used. The transition region in

is explored using the simplest non-perturbative models and NLO QCD. The data at very low

are described successfully by a combination of generalised vector meson dominance and Regge theory. From a NLO QCD fit to ZEUS data the gluon density in the proton is extracted in the range

. Data from NMC and BCDMS constrain the fit at large

. Assuming the NLO QCD description to be valid down to

, it is found that the

sea distribution is still rising at small

and the lowest

values whereas the gluon distribution is strongly suppressed.