Measurement of the proton structure function F2 and the total γ*p cross-section at low Q2 and low x

The ZEUS-experiment at HERA has significantly enhanced the kinematic coverage for low Q2 and low x inelastic e+p→e+X scattering with an upgrade of the ZEUS-detector in 1995 which extends the acceptance for small positron scattering angles. The upgrade included the modification of the beam pipe with low mass exit windows and the installation of a small electromagnetic sampling calorimeter, the Beam Pipe Calorimeter (BPC), to explore the region in Q2 of 0.11≤Q2≤0.65 GeV2. A shift of two rear uranium calorimeter (RCAL) modules and the small rear tracking detector (SRTD) closer to the beam together with a data sample taken with a shifted event vertex extended the Q2 coverage of the main detector down to 0.6 GeV2. Both data sets have been used to measure the proton structure function F2 and the total virtual photon-proton γ*p cross-section. Results are presented for 0.11≤Q2≤6.10 GeV2 and 2·10-6≤x≤7·10-4 along with a comparison to various models